Actually, I was planning to have a pipe connecting the two sumps, which
should make them effectively one sump. My problem is figuring out how large
the connecting pipe needs to be. If one pump fails I have 300 GPH coming
down each overflow, so I need 300 gph flow through a horizontal pipe, with
only the pressure of differing water levels to push it through the pipe.

Using two connected sumps will simplify the plumbing and keep the sumps
small enough that they can be removed through the stand doors.




"CapFusion" CapFusion...@hotmail..,com wrote in message
...

"Henry Etteldorf" wrote in message
. ..

[snip]
You are right in thinking you will only pump what you get via the
overflows,
with the momemtary exception of what it in the sump.

What happens when a pump stops.
Overflows reduce flow from 1200 gpm to 600 gpm, but not instantaneously.
You can visualize this as the level in tank will go down slightly and
there
will be less water in the overflow plumbing at any instant in time.
This
will cause an increase in the water in the sump. (Is the sump big
enough?
If it doesn't overflow with both pumps off this is not a concern.)
[/snip]

That really depend on the level on the overflow.
Depending on which or both pump stop.

Since there are two sump with pump, this make it very tricky and
complicated. [This kind of method I strongely NOT RECOMMENDED].


[snip]
What happens when one of the overflows plugs.
Sump #1 fill from 600 gpm overflow and pumps 600 gpm. Sump #2 doesn't
fill from overflow and pumps whatever is coming through connecting pipe
for
the sumps. You will get 1200 gpm from the two pumps momentarily
(possibly
overflowing the tank). Then you may get both pumps cavitating, causing
bubbles and heat.
[/snip]

Sump #1 working = Water will return to the main tank and maintain the
water
level of the overflow. From overflow where two pipe is split. Both pipe
will
still get water to distination sump #1 and #2. But sump #1 return water
back
to tank but not sump #2. Water level still maintain and continue the same
cycle until sump #1 no longer have water to return and water level from
the
main tank no longer can overflow to the filter.

Note - where all the water go? All water goto sump #2. Reason, pump from
the
sump #2 did not return any water that feed through the pipe.

Eventhough the sump #2 pump stop, there no prevention method or safe guard
from water keep on coming / feeding to any sump.
***[Please note, according previous thread, there no indication of safe
guard or prevention mention. ... like shutoff valve or floating valve etc
to
prevent water from coming into sump.]***

2nd note -
Best is to have one sump to hold any water that the main tank provide
according to water level is set from the overflow box. The water level is
set from the overflow water level.

CapFusion,...