RO pressure booster pump

[Pszemol]

Hi there,

My tap water pressure is around 40PSI, my membrane is 10gpd TFC.
I have heard the optimum pressure for RO membranes is from 65-120PSI.
I am considering a purchase of a booster pump but it is quite expensive.

What are benefits of increased pressure?
What are risks of increasing it too much?

[Marc Levenson]

The benefit is faster production, as the RO membrane works better under higher
pressure. I've been told it will actually extend the life of the membrane as
well. I would suggest you boost it up to about 80 psi.

Marc


Pszemol wrote:

> Hi there,
>
> My tap water pressure is around 40PSI, my membrane is 10gpd TFC.
> I have heard the optimum pressure for RO membranes is from 65-120PSI.
> I am considering a purchase of a booster pump but it is quite expensive.
>
> What are benefits of increased pressure?
> What are risks of increasing it too much?

--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

[Pszemol]

How much should I trust recommendation given by KENT?
They state optimum pressure for my membrane is 65PSI...
I am not sure if KENT is manufacturing their own membranes
or rather markets common membranes made by others?

Is there a maximum pressure you should never go over it?
Is is possible to damage membrane with too much pressure?

Does increased pressure improves quality of the permeate?
Does is decrease waste to product ratio?
I have found such statement when searching net...


"Marc Levenson" > wrote in message ...
> The benefit is faster production, as the RO membrane works better under higher
> pressure. I've been told it will actually extend the life of the membrane as
> well. I would suggest you boost it up to about 80 psi.
>
> Marc
>
>
> Pszemol wrote:
>
> > Hi there,
> >
> > My tap water pressure is around 40PSI, my membrane is 10gpd TFC.
> > I have heard the optimum pressure for RO membranes is from 65-120PSI.
> > I am considering a purchase of a booster pump but it is quite expensive.
> >
> > What are benefits of increased pressure?
> > What are risks of increasing it too much?
>
> --
> Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
> Business Page: http://www.sparklingfloorservice.com
> Marine Hobbyist: http://www.melevsreef.com
>
>

[CapFusion]

"Pszemol" > wrote in message
...
> How much should I trust recommendation given by KENT?
> They state optimum pressure for my membrane is 65PSI...
> I am not sure if KENT is manufacturing their own membranes
> or rather markets common membranes made by others?
>

Optimal pressure should be between 60 - 85. 120 is very dangerous level.


> Is there a maximum pressure you should never go over it?
> Is is possible to damage membrane with too much pressure?
>

I belived 120 PSI is too high that I read some where. [going by memory].


> Does increased pressure improves quality of the permeate?
> Does is decrease waste to product ratio?
> I have found such statement when searching net...
>

Higher prussure like 80 or so will give efficient operation output and
performance.

CapFusion,...

[Pszemol]

Marc and others: what PSW Tank Pressure Shut Off Switch should I pick?
I have three options: 40PSI, 60PSI, 80PSI... The store description tells me I need
to pick the pressure I want my collection tank to be filled with... but... I have no
collection tank - I need it to fill an empty bucket with a KENT float switch.
I have already pressure switch on the RO intake to switch tap off when the bucket
is full - I understand PSW switch is to switch the pump electrically off... Which to pick?

I am e-mailing the store c-support, but I need first hand users perspective as well :-)

BTW - what version do you guys have? 12V or 24V? Does it matter anyhow ?
Thanks.

"Marc Levenson" > wrote in message ...
> The benefit is faster production, as the RO membrane works better under higher
> pressure. I've been told it will actually extend the life of the membrane as
> well. I would suggest you boost it up to about 80 psi.
>
> Marc
>
>
> Pszemol wrote:
>
> > Hi there,
> >
> > My tap water pressure is around 40PSI, my membrane is 10gpd TFC.
> > I have heard the optimum pressure for RO membranes is from 65-120PSI.
> > I am considering a purchase of a booster pump but it is quite expensive.
> >
> > What are benefits of increased pressure?
> > What are risks of increasing it too much?
>
> --
> Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
> Business Page: http://www.sparklingfloorservice.com
> Marine Hobbyist: http://www.melevsreef.com
>
>

[Rod]

>Optimal pressure should be between 60 - 85. 120 is very dangerous level.
>

Yes, At least for most of the RO units sold to hobbyists. But there are many RO
units that require much higher PSI. That last unit I was maintaining required
225 PSI to run efficiantly. That was a 1700 GPD unit tho ;)
Rod Buehler
www.asplashoflife.com

[Raymond]

"Pszemol" > wrote in message >...
> Hi there,
>
> My tap water pressure is around 40PSI, my membrane is 10gpd TFC.
> I have heard the optimum pressure for RO membranes is from 65-120PSI.
> I am considering a purchase of a booster pump but it is quite expensive.
>
> What are benefits of increased pressure?
> What are risks of increasing it too much?

About three years (or so) back there was a response from Spectrapure
on this subject. 100PSI was the ideal for the maximum output without
dropping the quality of the purified water. 70 PSI is where the
membranes are tested. The quality of the filtered water, filtered
water quantity, and membrane life span were the areas improved when
increasing source water pressure. (the response was to a man that had
a source water pressure of 40psi) The response from spectrapure didn't
discuss how much pressure it would take to damage the membrane but I
wouldn't go above 100PSI. Also along these lines would be a membrane
flush kit. It is basicly a valve that bypasses the output restricter.
You simple turn the valve on and let it run for 30 seconds or so about
once a month. This flushes the membrane off and will extend its life.
I believe they are available from both Kent and Spectrapure. I don't
have the original response although I didn't do a search in this
newgroup....

Hope this was helpful....

[CapFusion]

"Rod" > wrote in message
...
> >Optimal pressure should be between 60 - 85. 120 is very dangerous level.
> >
>
> Yes, At least for most of the RO units sold to hobbyists. But there are
many RO
> units that require much higher PSI. That last unit I was maintaining
required
> 225 PSI to run efficiantly. That was a 1700 GPD unit tho ;)
> Rod Buehler
> www.asplashoflife.com

So far as those 225 PSI I have seen are like industry type that require more
pressure but for those normal hobbyist kind are normally at 60 - 85 PSI.

CapFusion,...

[CapFusion]

"Pszemol" > wrote in message
...
> Marc and others: what PSW Tank Pressure Shut Off Switch should I pick?
> I have three options: 40PSI, 60PSI, 80PSI... The store description tells
me I need
> to pick the pressure I want my collection tank to be filled with... but...
I have no
> collection tank - I need it to fill an empty bucket with a KENT float
switch.
> I have already pressure switch on the RO intake to switch tap off when the
bucket
> is full - I understand PSW switch is to switch the pump electrically
off... Which to pick?
>
> I am e-mailing the store c-support, but I need first hand users
perspective as well :-)
>
> BTW - what version do you guys have? 12V or 24V? Does it matter anyhow ?
> Thanks.
>

Pszemol, I am not sure I am valid to answer your question regarding which
PSI to get since I do not have or own one. But I do not see the point of
having one either (If I unstand your case). Are you talking about a booster
pump?
http://www.aquaticreefsystems.com/aquarium_pumps.htm
If so, you will need to get the pump that fit your need. If you have like 40
PSi, they get 80PSI booster pump to push your PSI upto 80 PSI. The above
link is about 70 to 120 PSI booster pump, regardless of your feed water
pussure.

Since you already have a float switch, all you need is to attach it to your
bucket.

CapFusion,...

[Marc Levenson]

CapFusion wrote:

> "Pszemol" > wrote in message
> ...
> > Marc and others: what PSW Tank Pressure Shut Off Switch should I pick?
> > I have three options: 40PSI, 60PSI, 80PSI... The store description tells
> me I need
> > to pick the pressure I want my collection tank to be filled with... but...
> I have no
> > collection tank - I need it to fill an empty bucket with a KENT float
> switch.
> > I have already pressure switch on the RO intake to switch tap off when the
> bucket
> > is full - I understand PSW switch is to switch the pump electrically
> off... Which to pick?
> >
> > I am e-mailing the store c-support, but I need first hand users
> perspective as well :-)
> >
> > BTW - what version do you guys have? 12V or 24V? Does it matter anyhow ?
> > Thanks.
> >

A float valve will not be absolutely trustworthy, because it may continue to
trickle out a minute amount of water, keeping your unit running all the time at
a very low rate. If that occurs, your water will actually be more polluted then
ever because of the super low flow rate.

If you want to use a float valve, use it as a safety/reminder. Then turn off
the RO/DI either before or after the unit, until you need to make fresh water.

Marc


--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

[Pszemol]

"Marc Levenson" > wrote in message ...
> A float valve will not be absolutely trustworthy, because it may continue to
> trickle out a minute amount of water, keeping your unit running all the time at
> a very low rate. If that occurs, your water will actually be more polluted then
> ever because of the super low flow rate.

What is the theory behind this effect? How is low flow affecting membrane?

> If you want to use a float valve, use it as a safety/reminder. Then turn off
> the RO/DI either before or after the unit, until you need to make fresh water.

Good idea - I will consider it. At first I was going to hook up the float switch
and have water constantly replenished. I had no idea it is a bad idea :-)

[Pszemol]

"CapFusion" > wrote in message ...
> Pszemol, I am not sure I am valid to answer your question regarding which
> PSI to get since I do not have or own one. But I do not see the point of
> having one either (If I unstand your case). Are you talking about a booster
> pump?
> http://www.aquaticreefsystems.com/aquarium_pumps.htm

Yes, I am thinking about a booster pump. But since I never had one
I am not comfortably making this decision... Is is worth it if I have
40PSI already? Will I have enough returns from this investments
boosting the pressure to the KENT-recommended 65PSI? Or maybe should
I override their recommendation and go with the crowd, boosting it to 80PSI?
Does this pump have precise regulation of the output pressure? How is it done?

> If so, you will need to get the pump that fit your need. If you have like 40
> PSi, they get 80PSI booster pump to push your PSI upto 80 PSI. The above
> link is about 70 to 120 PSI booster pump, regardless of your feed water
> pussure.

Thanks, I will look at it.

> Since you already have a float switch, all you need is to attach it to your
> bucket.

I have read they use other kind of switch to actualy turn off the pump
electricaly when the desired pressure is achieved. My float switch is
just shutting off the water exchaust and then, with back pressure, the
water intake. But the booster pump will operate constatly, even when
not needed. I have days, weeks sometimes without need to produce RO water.
How should I turn off my pump during inactivity periods?

[Pszemol]

Yes Raymond, thank you - I will google for this old thread.

"Raymond" > wrote in message om...
> About three years (or so) back there was a response from Spectrapure
> on this subject. 100PSI was the ideal for the maximum output without
> dropping the quality of the purified water. 70 PSI is where the
> membranes are tested. The quality of the filtered water, filtered
> water quantity, and membrane life span were the areas improved when
> increasing source water pressure. (the response was to a man that had
> a source water pressure of 40psi) The response from spectrapure didn't
> discuss how much pressure it would take to damage the membrane but I
> wouldn't go above 100PSI. Also along these lines would be a membrane
> flush kit. It is basicly a valve that bypasses the output restricter.
> You simple turn the valve on and let it run for 30 seconds or so about
> once a month. This flushes the membrane off and will extend its life.
> I believe they are available from both Kent and Spectrapure. I don't
> have the original response although I didn't do a search in this
> newgroup....
>
> Hope this was helpful....

[Marc Levenson]

I had a long conversation with a guy in the RO/DI business about this very subject, and
basically if your water is tricking in a tiny bit at a time (rather than 4gph), your
membrane is not able to keep the crap out of the water output. The flow is simply so
incredibly slow that it is able to travel right into your pure water.

So the very thing you hope to keep out of your system can/will trickle in extremely slowly
24 hours a day. Because your tank always evaporate a little bit of water, the float valve
never has quite enough water pushing it up to keep it closed, and your system will run
non-stop. And when that occurs, your waste line will be running non-stop as well. So
you'll be wasting water as well.

I didn't take notes ;) but what I was hearing made a lot of sense to me and confirmed my own
suspicions at that point. I always make 5 to 10g at a time, and turn off the system by
closing a valve on the (good) output.

Marc

Pszemol wrote:

> "Marc Levenson" > wrote in message ...
> > A float valve will not be absolutely trustworthy, because it may continue to
> > trickle out a minute amount of water, keeping your unit running all the time at
> > a very low rate. If that occurs, your water will actually be more polluted then
> > ever because of the super low flow rate.
>
> What is the theory behind this effect? How is low flow affecting membrane?
>
> > If you want to use a float valve, use it as a safety/reminder. Then turn off
> > the RO/DI either before or after the unit, until you need to make fresh water.
>
> Good idea - I will consider it. At first I was going to hook up the float switch
> and have water constantly replenished. I had no idea it is a bad idea :-)

--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

[Pszemol]

But what you do defeats the purpose of havin automatic top-off system...
Is there another way to do the same job without human/manual operations?

"Marc Levenson" > wrote in message ...
> I had a long conversation with a guy in the RO/DI business about this very subject, and
> basically if your water is tricking in a tiny bit at a time (rather than 4gph), your
> membrane is not able to keep the crap out of the water output. The flow is simply so
> incredibly slow that it is able to travel right into your pure water.
>
> So the very thing you hope to keep out of your system can/will trickle in extremely slowly
> 24 hours a day. Because your tank always evaporate a little bit of water, the float valve
> never has quite enough water pushing it up to keep it closed, and your system will run
> non-stop. And when that occurs, your waste line will be running non-stop as well. So
> you'll be wasting water as well.
>
> I didn't take notes ;) but what I was hearing made a lot of sense to me and confirmed my own
> suspicions at that point. I always make 5 to 10g at a time, and turn off the system by
> closing a valve on the (good) output.

[Raymond]

"Pszemol" > wrote in message >...
> I have read they use other kind of switch to actualy turn off the pump
> electricaly when the desired pressure is achieved. My float switch is
> just shutting off the water exchaust and then, with back pressure, the
> water intake. But the booster pump will operate constatly, even when
> not needed. I have days, weeks sometimes without need to produce RO water.
> How should I turn off my pump during inactivity periods?

I think the difference you are looking for is a pressure switch versus
a pressure valve. Most RO systems use a pressure valve to turn off the
source water when the filtered water output line reaches a given
pressure. This works great for the drinking water kits and float valve
top off systems but it doesn't allow for turning power on/off to the
booster pump. You need to add a pressure *switch* that will turn the
power off to the booster pump when the desired pressure is reached....

[Chimera]

Whoa.
From what I know about RO, a semi-permeable membrane is used to reject
molecules (?) larger than H20.
How would low pressure defeat the membrane? Must be the design of the
unit(does the source water get around the membrane?) , not the
physics.


Marc Levenson > wrote in message >...
> I had a long conversation with a guy in the RO/DI business about this very subject, and
> basically if your water is tricking in a tiny bit at a time (rather than 4gph), your
> membrane is not able to keep the crap out of the water output. The flow is simply so
> incredibly slow that it is able to travel right into your pure water.
>
> So the very thing you hope to keep out of your system can/will trickle in extremely slowly
> 24 hours a day. Because your tank always evaporate a little bit of water, the float valve
> never has quite enough water pushing it up to keep it closed, and your system will run
> non-stop. And when that occurs, your waste line will be running non-stop as well. So
> you'll be wasting water as well.
>
> I didn't take notes ;) but what I was hearing made a lot of sense to me and confirmed my own
> suspicions at that point. I always make 5 to 10g at a time, and turn off the system by
> closing a valve on the (good) output.
>
> Marc
>
> Pszemol wrote:
>
> > "Marc Levenson" > wrote in message ...
> > > A float valve will not be absolutely trustworthy, because it may continue to
> > > trickle out a minute amount of water, keeping your unit running all the time at
> > > a very low rate. If that occurs, your water will actually be more polluted then
> > > ever because of the super low flow rate.
> >
> > What is the theory behind this effect? How is low flow affecting membrane?
> >
> > > If you want to use a float valve, use it as a safety/reminder. Then turn off
> > > the RO/DI either before or after the unit, until you need to make fresh water.
> >
> > Good idea - I will consider it. At first I was going to hook up the float switch
> > and have water constantly replenished. I had no idea it is a bad idea :-)

[CapFusion]

"Pszemol" > wrote in message
...
> "Marc Levenson" > wrote in message
...
> > A float valve will not be absolutely trustworthy, because it may
continue to
> > trickle out a minute amount of water, keeping your unit running all the
time at
> > a very low rate. If that occurs, your water will actually be more
polluted then
> > ever because of the super low flow rate.
>
> What is the theory behind this effect? How is low flow affecting membrane?
>

Any water pressure over 35 to 40 P.S.I. should be sufficient to run in
reverse osmosis unit correctly. Keep in mind however that the more pressure
the easier the water will have penetrating the membrane element itself.
Running a system with too little pressure will cause underproduction and
over waste.



> > If you want to use a float valve, use it as a safety/reminder. Then
turn off
> > the RO/DI either before or after the unit, until you need to make fresh
water.
>
> Good idea - I will consider it. At first I was going to hook up the float
switch
> and have water constantly replenished. I had no idea it is a bad idea :-)

I prefer not to have float switch in any part of any system but anyone need
to have it then be caution if using with endless supply of water. But if it
setup coming from a resoviour or a bladder without endless source then it is
GOOD.

CapFusion,...

[CapFusion]

"Pszemol" > wrote in message
...
> "CapFusion" > wrote in message
...
> > Pszemol, I am not sure I am valid to answer your question regarding
which
> > PSI to get since I do not have or own one. But I do not see the point of
> > having one either (If I unstand your case). Are you talking about a
booster
> > pump?
> > http://www.aquaticreefsystems.com/aquarium_pumps.htm
>
> Yes, I am thinking about a booster pump. But since I never had one
> I am not comfortably making this decision... Is is worth it if I have
> 40PSI already? Will I have enough returns from this investments
> boosting the pressure to the KENT-recommended 65PSI? Or maybe should
> I override their recommendation and go with the crowd, boosting it to
80PSI?
> Does this pump have precise regulation of the output pressure? How is it
done?
>

The one I saw like 550 series, it can run intermittently / demand by
presssure / delivery mode by a switch.

Regarding "precise regulation", I am not to sure if it "precise" as to
speaking but you can ask ARS [John] for detail information. Having your
feed or pressure about 80PSI is good for your RO to produce pure water. At
80 PSI, it can penatrate the membrane for better efficient output and will
produce less waste. Getting about 40 PSI will be less efficient and produce
more waste water. Optimal recommend is about 80 PSI or so.


> I have read they use other kind of switch to actualy turn off the pump
> electricaly when the desired pressure is achieved. My float switch is
> just shutting off the water exchaust and then, with back pressure, the
> water intake. But the booster pump will operate constatly, even when
> not needed. I have days, weeks sometimes without need to produce RO water.
> How should I turn off my pump during inactivity periods?

I guess the 550 series pump does the same as the one you are referring to?

CapFusion,...

[CapFusion]

IMHO, I prefer not to have any auto top-off or auto switch that feed either
the sump or the tank with the water level get low. I have 100G tank 40G sump
that will evaporate abut 5 - 10G a week or so. When it evaporate, I just use
from a resovour or from a water dispenser. No big deal as for manul work.
But it a big deal if the auto-shut off switch / valve fail to turn off the
water, it will cause overflow both to the sump and the tank. I may need to
call Marc for his "Sparkling Floor Service" to clean up my floor / carpet.
The only auto is the Auto-Valve from the RO. You do not want to know that
your floor got flooded when you get home from work / school or whatever. It
will become another expense to fix.

CapFusion,...


"Pszemol" > wrote in message
...
> But what you do defeats the purpose of havin automatic top-off system...
> Is there another way to do the same job without human/manual operations?
>
> "Marc Levenson" > wrote in message
...
> > I had a long conversation with a guy in the RO/DI business about this
very subject, and
> > basically if your water is tricking in a tiny bit at a time (rather than
4gph), your
> > membrane is not able to keep the crap out of the water output. The flow
is simply so
> > incredibly slow that it is able to travel right into your pure water.
> >
> > So the very thing you hope to keep out of your system can/will trickle
in extremely slowly
> > 24 hours a day. Because your tank always evaporate a little bit of
water, the float valve
> > never has quite enough water pushing it up to keep it closed, and your
system will run
> > non-stop. And when that occurs, your waste line will be running
non-stop as well. So
> > you'll be wasting water as well.
> >
> > I didn't take notes ;) but what I was hearing made a lot of sense to me
and confirmed my own
> > suspicions at that point. I always make 5 to 10g at a time, and turn
off the system by
> > closing a valve on the (good) output.
>

[Pszemol]

"Chimera" > wrote in message m...
> Whoa.
> From what I know about RO, a semi-permeable membrane is used to reject
> molecules (?) larger than H20.
> How would low pressure defeat the membrane? Must be the design of the
> unit(does the source water get around the membrane?) , not the
> physics.

I was confused reading Marcs words the same way...
And if membrane is leaking, it would leak more with higher pressure, right?

[Marc Levenson]

Having an auto top off feature is wonderful, but it has to be controllable. If' I have to go out
of town for a few days, and the switch fails/jams/etc... 30 minutes after I leave, water could
continue to flow for days until I get back.

However, making 30 gals of water, then hooking up a switch/float valve to that is a good method of
protection. Once a week you fill up the resevoir, and then for 7 days you let the resevoir top
off your tank.

Marc


Pszemol wrote:

> But what you do defeats the purpose of havin automatic top-off system...
> Is there another way to do the same job without human/manual operations?
>

--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

[Rod]

>You do not want to know that
>your floor got flooded when you get home from work / school or whatever. It
>will become another expense to fix.

I agree.. nor do you want your tank flooded with fresh water.. Float switches
in reef tanks can and will fail due to calcium deposit build up and even salt
creep. If you must use a float switch to control you top off unit, I recommend
inspecting and cleaning weekly.
Rod Buehler
www.asplashoflife.com

[Pszemol]

Assuming the most pessimistic scenario, the switch will fail 30 minutes after you
leave and you will have 30 gals of fresh water in your tank.

Maybe the solution is to have to float valves/switches?
One for regular top-off, and the second and inch or so higher, for safety.

It would greatly improve your chances of coming home and finding
everything in order... Both probabilities of switch failure will multiply giving even
smaller probability of overall failure - at least that is what I remember from school ;-)

"Marc Levenson" > wrote in message ...
> Having an auto top off feature is wonderful, but it has to be controllable. If' I have to go out
> of town for a few days, and the switch fails/jams/etc... 30 minutes after I leave, water could
> continue to flow for days until I get back.
>
> However, making 30 gals of water, then hooking up a switch/float valve to that is a good method of
> protection. Once a week you fill up the resevoir, and then for 7 days you let the resevoir top
> off your tank.
>
> Marc
>
>
> Pszemol wrote:
>
> > But what you do defeats the purpose of havin automatic top-off system...
> > Is there another way to do the same job without human/manual operations?
> >
>
> --
> Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
> Business Page: http://www.sparklingfloorservice.com
> Marine Hobbyist: http://www.melevsreef.com
>
>

[CapFusion]

"Rod" > wrote in message
...
> >You do not want to know that
> >your floor got flooded when you get home from work / school or whatever.
It
> >will become another expense to fix.
>
> I agree.. nor do you want your tank flooded with fresh water.. Float
switches
> in reef tanks can and will fail due to calcium deposit build up and even
salt
> creep. If you must use a float switch to control you top off unit, I
recommend
> inspecting and cleaning weekly.
> Rod Buehler
> www.asplashoflife.com

If auto-topoff require, I would hook it up to a resoviour that hold certain
amount. If any auto-switch / float etc fail, it will just empty the resovour
only.

CapFusion,...

[Raymond]

"Pszemol" > wrote in message >...
> "Chimera" > wrote in message m...
> > Whoa.
> > From what I know about RO, a semi-permeable membrane is used to reject
> > molecules (?) larger than H20.
> > How would low pressure defeat the membrane? Must be the design of the
> > unit(does the source water get around the membrane?) , not the
> > physics.
>
> I was confused reading Marcs words the same way...
> And if membrane is leaking, it would leak more with higher pressure, right?

As I understand it the loss of purity at low pressure is due to the
slow rate at which the clean water is going through the membrane. The
membranes are manufactured with defects. That is why they let a small
percentage of impurities through. The membrane requires a certain
amount of pressure to force the pure water through. The impurities go
through the defects at a much lower pressure. As the pressure rises
the amount of impurities forced through the defects goes up but not at
the same rate as the pure water. In other words the defects are little
holes in the membrane. At lower pressure the only water getting
through is through these defects. As the pressure rises you start to
get water through all of the membrane and the pure water then dilutes
the source water leaking through the defects down to a very low level.
The lower the pressure the higher the percentage of impurities. The
membranes are tested and the specs given are at 65-70 PSI. My
understanding is that at some point, as the pressure goes up,
impurities are forced through the membrane. This means there is a top
end limit (prior to bursting the membrane) at which you should operate
the filter at. If memory serves the optimum limit was at 100 PSI. If I
had the cash to drop on a booster pump, I would, and I would set the
pressure to 100PSI. Actually I would probably write the manufacturer
and ask the question again as this information is several years old
now....
FWIW

[Pszemol]

Yes, it makes sense. I did not consider defects in the membrane film.
Thank you.

"Raymond" > wrote in message om...
> As I understand it the loss of purity at low pressure is due to the
> slow rate at which the clean water is going through the membrane. The
> membranes are manufactured with defects. That is why they let a small
> percentage of impurities through. The membrane requires a certain
> amount of pressure to force the pure water through. The impurities go
> through the defects at a much lower pressure. As the pressure rises
> the amount of impurities forced through the defects goes up but not at
> the same rate as the pure water. In other words the defects are little
> holes in the membrane. At lower pressure the only water getting
> through is through these defects. As the pressure rises you start to
> get water through all of the membrane and the pure water then dilutes
> the source water leaking through the defects down to a very low level.
> The lower the pressure the higher the percentage of impurities. The
> membranes are tested and the specs given are at 65-70 PSI. My
> understanding is that at some point, as the pressure goes up,
> impurities are forced through the membrane. This means there is a top
> end limit (prior to bursting the membrane) at which you should operate
> the filter at. If memory serves the optimum limit was at 100 PSI. If I
> had the cash to drop on a booster pump, I would, and I would set the
> pressure to 100PSI. Actually I would probably write the manufacturer
> and ask the question again as this information is several years old
> now....
> FWIW

[Raymond]

What I am doing addresses this except that I don't top-off with just
RO water. I mix up lime water (Kalkwasser) to dose with. I had all the
same worries. If the float valve sticks and it is connected to an
endless supply of water or even a large container of water....

So I mix my lime water in a container. The container has a float valve
with a mechanical valve that is used to refill the container with RO
water. I leave the mechanical valve open unless I'm going to be gone
and not available to check on it or I want to maintain the strength of
the mix in the container. (which I do frequently) The makeup water is
pulled from the container with a dosing pump. The dosing pump is set
to dose at a rate that matches water evaperation + ~10% or so. (This
allows for varying evaperation rates due to changes in humidity
through out the year) The dosing pump is plugged into a float switch
that turns it off if the water gets to high in the sump. The float
switch is plugged into a mechanical wall timer that turns on at night
for about 12 hours. This causes the days evaperation to be replaced
with what ever is in the container (kalkwasser) through the night at a
slow rate. If I missed on the dosing rate then the float switch will
turn it off. If the float switch sticks then it still will only add a
little too much until the timer turns it off for day operation and
even if the timer were to fail then it still can only add as much as
is in the container unless I left the valve on.

Now this is a little different because of the lime water but all but
the day/night timer would still be applicable and make it quite safe.

Just my two cents...

"Pszemol" > wrote in message >...
> Assuming the most pessimistic scenario, the switch will fail 30 minutes after you
> leave and you will have 30 gals of fresh water in your tank.
>
> Maybe the solution is to have to float valves/switches?
> One for regular top-off, and the second and inch or so higher, for safety.
>
> It would greatly improve your chances of coming home and finding
> everything in order... Both probabilities of switch failure will multiply giving even
> smaller probability of overall failure - at least that is what I remember from school ;-)
>
> "Marc Levenson" > wrote in message ...
> > Having an auto top off feature is wonderful, but it has to be controllable. If' I have to go out
> > of town for a few days, and the switch fails/jams/etc... 30 minutes after I leave, water could
> > continue to flow for days until I get back.
> >
> > However, making 30 gals of water, then hooking up a switch/float valve to that is a good method of
> > protection. Once a week you fill up the resevoir, and then for 7 days you let the resevoir top
> > off your tank.
> >
> > Marc
> >
> >
> > Pszemol wrote:
> >
> > > But what you do defeats the purpose of havin automatic top-off system...
> > > Is there another way to do the same job without human/manual operations?
> > >
> >
> > --
> > Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
> > Business Page: http://www.sparklingfloorservice.com
> > Marine Hobbyist: http://www.melevsreef.com
> >
> >

[Marc Levenson]

Raymond's system is the only way I'd dose Kalkwasser. They have some very nice pumps that will only add
up to 4g a day (some are designed for less per day, others for more), but the one I liked was $200!

Using dual float switches will work fine, if you use a small powerhead to feed the water. However, if
you want to use the Kent Float Valve, you don't have that option. It is a plastic air filled device
that falls downward to let water in, and as the water level rises, so does the float arm until the feed
line is blocked. This is the kind many use, but I don't recommend them being hooked up directly to the
RO/DI. It'll work fine with a gravity driven resevoir though.

Marc


Pszemol wrote:

> Assuming the most pessimistic scenario, the switch will fail 30 minutes after you
> leave and you will have 30 gals of fresh water in your tank.
>
> Maybe the solution is to have to float valves/switches?
> One for regular top-off, and the second and inch or so higher, for safety.
>
> It would greatly improve your chances of coming home and finding
> everything in order... Both probabilities of switch failure will multiply giving even
> smaller probability of overall failure - at least that is what I remember from school ;-)
>
>

--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

[Marc Levenson]

http://www.premiumaquatics.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=PA&Product_Code=SP-LLC-S&Category_Code=Dosers

That might be the perfect solution to what you want. It better be for $85 + shipping.

Marc


Pszemol wrote:

> Assuming the most pessimistic scenario, the switch will fail 30 minutes after you
> leave and you will have 30 gals of fresh water in your tank.
>
> Maybe the solution is to have to float valves/switches?
> One for regular top-off, and the second and inch or so higher, for safety.
>
> It would greatly improve your chances of coming home and finding
> everything in order... Both probabilities of switch failure will multiply giving even
> smaller probability of overall failure - at least that is what I remember from school ;-)
>

--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

[Raymond]

Marc Levenson > wrote in message >...
> http://www.premiumaquatics.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=PA&Product_Code=SP-LLC-S&Category_Code=Dosers
>
> That might be the perfect solution to what you want. It better be for $85 + shipping.
>
> Marc

The liquid level control is a great product from the RO membrane
perspective but I'm not so sure it is all that great from a Reef tank
perspective depending on how it is used. When the water level reaches
the low water point the "switch" turns on and doesn't turn off until
the water level has risen ~1 inch. If the water is being pumped into
the tank/sump/whatever then the rise in water happens quickly and you
would see a bounce in salinity. If it is hooked straight to your RO
system and you have a pressure (bladder) tank then the water is still
added quickly. The design is for connecting straight out of the RO
filter without any storage tank so the water would be added at the
rate the membrane can pass it. As long as that is the way it is being
used then I would agree that this may indeed be the perfect solution.

[Pszemol]

"Raymond" > wrote in message om...
> The liquid level control is a great product from the RO membrane
> perspective but I'm not so sure it is all that great from a Reef tank
> perspective depending on how it is used. When the water level reaches
> the low water point the "switch" turns on and doesn't turn off until
> the water level has risen ~1 inch. If the water is being pumped into
> the tank/sump/whatever then the rise in water happens quickly and you
> would see a bounce in salinity. If it is hooked straight to your RO
> system and you have a pressure (bladder) tank then the water is still
> added quickly. The design is for connecting straight out of the RO
> filter without any storage tank so the water would be added at the
> rate the membrane can pass it. As long as that is the way it is being
> used then I would agree that this may indeed be the perfect solution.

My filter is giving 10gpd max when conditions are optimal.
With my lower pressure and colder water is gives less...
It should be ok :-)