Overflow return pipe sucks float to the bottom

I recently purchased a used 90 gallon All-Glass overflow aquarium. I'm
new to this type of system so I'm not sure what to expect. The system
seems to be functioning normally with the exception of the float inside
the return pipe. It is supposed to float on the surface of the water
to quite the flow of water. It does this for a minute or so and then
gets sucked down, completely cutting off the flow of water. Then it
pops back up to the surface when the water level rises. It continues
to cycle like this causing a noisy sucking sound every time the float
is pulled down. I'm wondering If I've got too large of a pump,
providing more water than the return can handle. It's 950 GPH pump.
There is also a small air hole in the top of the float. If I make this
hole larger will it prevent the presure from building too hight?

I've never had good luck with those types of overflow apparatus. They
usually end up in the trash, and I make a Durso. Sounds like the flow
may be too high for the overflow box.


Durso Standpipe info:
http://www.wetwebmedia.com/dursopipefaqs.htm

billy

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"Mike" wrote in message
oups.com...
I recently purchased a used 90 gallon All-Glass overflow aquarium.
I'm
new to this type of system so I'm not sure what to expect. The
system
seems to be functioning normally with the exception of the float
inside
the return pipe. It is supposed to float on the surface of the
water
to quite the flow of water. It does this for a minute or so and
then
gets sucked down, completely cutting off the flow of water. Then
it
pops back up to the surface when the water level rises. It
continues
to cycle like this causing a noisy sucking sound every time the
float
is pulled down. I'm wondering If I've got too large of a pump,
providing more water than the return can handle. It's 950 GPH
pump.
There is also a small air hole in the top of the float. If I make
this
hole larger will it prevent the presure from building too hight?

Thanks for the info. The Durso Standpipe web site was helpful:
http://www.dursostandpipes.com/
Mike