Suggestions on how to SLOW down back siphon from return

wetWolger · 03/08/2015, 12:03 PM

So this is a new one for me, and I have not found many others with the same issue. Because of some space constraints I have to have my return pump at a weird angle on my new build.

This normally functions fine, but the issue is when I turn the pump off, the return lines start "sipping" air until it breaks the siphon. The issue is that it pushes this air down the return line and back out the pump, and due to how I have the pump currently mounted it causes it to loose it's prime.

The sump can 100% hold all the water that is siphoned into it.

So I am looking for a way to slow down the back siphon so that that as it sucks air in there is not enough water velocity to push it all the way to the pump. If it's slow enough I also expect it wont just "sip" air out like it currently does as it back siphons either.

The only idea I have is a check valve (but I am open to any creative suggestions as well!). I normally am not a fan of check valves, but since this wont prevent a flood, just maintaining the pump's prime, it seems like it's an okay solution.

What sucks most about the check valve is the reduction in flow. So I want to pick the check valve that will have the less head loss (and not necessarily be the most reliable).

I do see two possible options with the check valves:

1) I cut a section out of my return plumbing and put in a true union flapper check valve (I assume this version would have the least head loss?)

2) I could put in 1/2in loc line check valves on my two loc line return lines

I can't seem to find my information about how much the loc line check valves restrict flow. Does any one know much about them?

What would be the best choice for slowing the return siphon, while maintaining the maximum flow?

mechanix23 · 03/08/2015, 01:51 PM

From your description, it sounds like you're getting air trapped in the impeller. The only choice for prevent that is your number 1 option. The other option is to use an external pump due to lack of sump room and install a backwards check valve at the top of your return. This option will have no-head loss. When you shut the return pump off, the check valve will break the siphon by letting air in. I think I saw this on Melev's Reef. It's on YouTube.

03/08/2015, 12:03 PM	#1
wetWolger Registered Member Join Date: Oct 2005 Location: Colorado Posts: 1,955	Suggestions on how to SLOW down back siphon from return So this is a new one for me, and I have not found many others with the same issue. Because of some space constraints I have to have my return pump at a weird angle on my new build. This normally functions fine, but the issue is when I turn the pump off, the return lines start "sipping" air until it breaks the siphon. The issue is that it pushes this air down the return line and back out the pump, and due to how I have the pump currently mounted it causes it to loose it's prime. The sump can 100% hold all the water that is siphoned into it. So I am looking for a way to slow down the back siphon so that that as it sucks air in there is not enough water velocity to push it all the way to the pump. If it's slow enough I also expect it wont just "sip" air out like it currently does as it back siphons either. The only idea I have is a check valve (but I am open to any creative suggestions as well!). I normally am not a fan of check valves, but since this wont prevent a flood, just maintaining the pump's prime, it seems like it's an okay solution. What sucks most about the check valve is the reduction in flow. So I want to pick the check valve that will have the less head loss (and not necessarily be the most reliable). I do see two possible options with the check valves: 1) I cut a section out of my return plumbing and put in a true union flapper check valve (I assume this version would have the least head loss?) 2) I could put in 1/2in loc line check valves on my two loc line return lines I can't seem to find my information about how much the loc line check valves restrict flow. Does any one know much about them? What would be the best choice for slowing the return siphon, while maintaining the maximum flow? __________________ cheers, jent d-_-b Current Tank Info: 66gal = 32x24x20

03/08/2015, 01:51 PM	#2
mechanix23 Registered Member Join Date: May 2012 Location: Collinsville, OK Posts: 29	From your description, it sounds like you're getting air trapped in the impeller. The only choice for prevent that is your number 1 option. The other option is to use an external pump due to lack of sump room and install a backwards check valve at the top of your return. This option will have no-head loss. When you shut the return pump off, the check valve will break the siphon by letting air in. I think I saw this on Melev's Reef. It's on YouTube.