Turn off pump, siphon happens, turn on pump = weak flow

[qguy]

Got a pump in a sump, when I turn off the pump, siphon happens. I turn on the pump and then the flow is reduced. What I need to do is turn off the pump. Remove the hose, turn om the pump and connect the hose.
Never had this problem when the pump was inside the main tank, its only when it was in sump about 5 feet height.

Any suggestions on what to do and what is happening ?

Rio 17HF - i know its an inexpensive pump, but got no funds to replace it right now, there must be a solution to my dilemma.

Thanks

 

[ragin_cajun]

Hmmm....do you have a check valve in the return line? I'm guessing the 5 foot height of water is enough pressure on the pump to keep it from starting up?

 

[qguy]

no check valve, but the pump starts and water flows to the main tank, but the flow is from my guess half the rate...

 

[ragin_cajun]

http://www.riopump.net/products_pumps/hyperflow_desc.html

Yep, that's about right according to the manufacturers output curves. A little over 1000 GPH with 1 foot of head height. A little over 500 GPH with 5 feet of head height.

 

[qguy]

the pump works fine when I turn it on, with no hose, I connect the hose and its still ok, Turn off and then restart and i get a reduce flow rate. Nothing changes except for the turn on and turn off process. Basically the flow is reduce when I do a turn off and then turn on cycle

 

[DDK]

Why dont you just drill a hole at the top of the return?

http://www.reefkeeping.com/issues/2008-01/newbie/images/tn_image011_jpg.jpg

this will break the siphon. The hole doesnt need to be anywhere near that big. A small 1/16th inch hole will do exactly the same thing.

 

[DN328]

So are you saying that when you turn the return pump back on, it never reaches "equilibrium" between sump and tank again? Or, does it just take a long time to reach the point that the water level is as it should be?

If the pump isn't able to return back to the tank then, perhaps breaking the siphon earlier as suggested will help with that and so you don't have too much head starting up?

 

[qguy]

When I turn the pump back on, the GPH is reduced. even if I remove the hose from the pump the GPH is still reduced.

Breaking the siphon does not help. kinda weird, but what I need to do is Turn off the pump. remove the hose from the pump, turn on and then connect the hose.