Can't stop the siphon!

[Seajuice]

I have an auto top off system with a float valve in the sump and a pump in a 25 gal. vat. The system works well but when the vat is full and the pump goes off the water still flows into my sump. The pump is pretty low into the vat and I have put a couple of coils in the tubing. I'm sure there is a good solution but I can't seem to come up with it. I thought of a check valve but that just prevents flow in the reverse direction.
Very frustrating, thanks in advance for anyones help.
Feeling very stupid that I can't think of a solution!

 

[manderx]

the end of the tubing that water drains out of into the sump has to be up above both the water level in the sump and the water level (not just the pump) in the reservior vat.

 

[scottfarcuz]

Put the tubing output into the main tank. Unless you have a very tall storage container it should be higher. I run mine into the overflow box.

 

[Tremelle]

Drill a hole in the tubing just above the highest water level in the sump. When the water flow stops, the hole will introduce air into the line to break the syphon. When water is flowing you may get alittle spirt from the hole but that water will just drip into the sump. That is the same premise of the return lines into the main tank.

 

[RicksReefs]

as manderx said, if both ends are submerged or the outflow is below the waterline of the vat, you'll get a siphon.

 

[Spuds725]

You could also put a small hole high in your line in storage container-- check valve won't do anything unless you can find some type of spring loaded one that will seat under low pressure (top off pump off)--I'm not sure if they make such a thing for this application... I know this type of valve exists in hydraulic systems but obviously would not be suitable in this application.

 

[Seajuice]

Thanks! I'm going to try putting a small hole in the tubing that is currently in the storage container.

 

[Sk8r]

Put a lid on the storage container. An old salt bucket works fine, if a 5 gallon serves, with a notch in the top to accommodate the outgoing hose and incoming cord.

 

[scrager]

putting a lid on won't stop a siphon

you need a siphon break hole above the water level of the vat or put the output higher than the water level of the vat. i run mine to the overflow and it works great. also has lots of time to mix the fresh water into the saltwater before returning to the tank.
only thing is that the end needs to NOT be submerged in the overflow. this will create a siphon from the overflow to the vat.

 

[Sk8r]

No, no, I mean that once you put the hole near the waterline, it will spray when the pump is working, and you could get spatter outside the bucket. Hence the lid, to prevent it spattering your cabinet. Sorry about that---should have specified.