How to prevent backflow in drilled tanks?

[cvrle1]

Hello everyone,

Was doing some reading last night, but couldnt find good info on how to prevent backflow of water from the return piping in a drilled tank. Consensus is not to use check valves, and similar, as they will clog up and not work. For folks that are using over the tank returns, it is easy to control by drilling a hole that would break siphon. How do you break siphon for tank with drilled returns though?

Tried finding pics and such, but wasnt ale to get any conclusive answers.

Thanks for the help.

 

[ihavecrabs]

It would be easier to help and understand your specific conditions with a picture of your overflow.

Edit: misunderstood question

Are you talking about backflow when your return pump turns off, returning water to your sump?

In this case, typically your return flows through your overflow. You can drill a spot facing down here to eliminate the siphon. Mine go through the back of the tank and I use loc-line tubing to bring the returns to the waters top and drill a small hole 1/2" below that point.

 

[redfishbluefish]

I would never us a check valve with the exception of Melev's reverse check valve. Here's a video that explains it:

 

[KrisReef]

Drill a hole? I've done that before. I drilled a small hole into the horizontal return pipe where it pointed down into the tank so that any spray or leakage was aimed into the tank.
Check valves can fail, and holes can get plugged with detritus, algae, etc. Be careful.
HTh.

Come to think of it, I drilled the tiny hole at an angle through the pipe (pointing in the direction of the return flow) so that the holes would tend to draw in air vs. spout water when the return pump is running.

 

[cvrle1]

It would be easier to help and understand your specific conditions with a picture of your overflow.

Edit: misunderstood question

Are you talking about backflow when your return pump turns off, returning water to your sump?

In this case, typically your return flows through your overflow. You can drill a spot facing down here to eliminate the siphon. Mine go through the back of the tank and I use loc-line tubing to bring the returns to the waters top and drill a small hole 1/2" below that point.

Yes, I was thinking about back flow when return pump turns off (in case of power outage for example) I get that it goes through overflow, but water is also sucked in through return pipes back into the sump. If return pipe is for example 2 inches below the water surface in DT, that will be a lot of water sucked back into the sump.

Locline was missing piece in my understanding. I was under the impression that majority of folks use return for water movement in the DT, thus having return deep in the water, but it seems that isnt the case. I could be wrong, but my understanding now is that majority use locline and aim it near the top so that they break surface tension, and then use proper wavemakers and pumps for actual water movement inside the tank.

 

[falc]

I am no plumbing expert but I picked up a used tank that had the return drilled too low and I used 2 pvc 90's to bring it just above the waterline and then used locline to direct the flow where I wanted it. You could also drill a couple small holes in the PVC at the waterline as extra protection in case the locline gets pushed too far under the surface. Sorry, not the best picture.

 

[ihavecrabs]

Yes, I was thinking about back flow when return pump turns off (in case of power outage for example) I get that it goes through overflow, but water is also sucked in through return pipes back into the sump. If return pipe is for example 2 inches below the water surface in DT, that will be a lot of water sucked back into the sump.

Locline was missing piece in my understanding. I was under the impression that majority of folks use return for water movement in the DT, thus having return deep in the water, but it seems that isnt the case. I could be wrong, but my understanding now is that majority use locline and aim it near the top so that they break surface tension, and then use proper wavemakers and pumps for actual water movement inside the tank.

Having that low and for flow sounds like a closed loop system. Returns are generally close to the top for the siphon reason. You could run loc-line to the top and then drill a hole close to the surface (make sure it is pointing sideways or down though!

 

[Travis Stewart]

I use a check valve and Check often for clogs, but have had great success with one. I also plumbed it close to the return pump so I can see it easily.

 

[nickeg79]

small hole angled down and in under the return line for immediate siphon break when return pump is off...just keep the hole cleared of salt buildup etc

 

[Ron Reefman]

I even add a john guest 90 degree elbow (one end threaded to screw into the return line and a push/pull fitting at the other end) to the anti siphon hole. That way it can be set so it's just at or just below the water surface. It also helps with breaking the water surface tension and breaks the siphon almost instantly. My tank only backflows about a gallon before the siphon breaks. Oh, and if you need more 'reach' to get the elbow near the surface, you can add a small bit of pipe in the push/pull fitting.

20180717_110047 by Ron Lindensmith, on Flickr

 

[cvrle1]

Thanks everyone for info. This now gives me better understanding on how to go about this part of plumbing at least.

 

[beaslbob]

as long as the return outlet has any part above the tank water level, no syphon results.

 

[Stanzo13]

Drill a hole? I've done that before. I drilled a small hole into the horizontal return pipe where it pointed down into the tank so that any spray or leakage was aimed into the tank.
Check valves can fail, and holes can get plugged with detritus, algae, etc. Be careful.
HTh.

Come to think of it, I drilled the tiny hole at an angle through the pipe (pointing in the direction of the return flow) so that the holes would tend to draw in air vs. spout water when the return pump is running.

I am literally going to do this. What a great idea, thanks. (For the overflow side) but... What about the return side that will always have pressure behind it

 

[jjflounder1]

I use both a check valve just above my return pump ...
And small holes in the lock-line fitting..... Gives me redundancy ...

 

[JumboShrimp]

I have these flaired return ends partially out of the water; no siphon ever forms when the power gets cut / pump goes into feeing mode.