# Plumbin: Check valve to prevent draining of the tank ?



## Gilles (Oct 12, 2007)

Quick question. I am in the process of plumbing my 120 gallon tank and 30 gallon sump. I have incorporated my tubing inside my background of the aquarium. This means that the tubing outlets are below water level.

I did this because i did not want the tubing inside my tank to be vissible to the human eye. However; this brought another "problem" into my tank. When the power goes "out", my tank would drain untill the first point in my tank where the tubing can suck in air. I hope you understand what i mean.

To compensate, i thought of using a 1 1/2" (32mm) check valve but they have a very high resistance, causing my pump to loose a lot of "power". Now, the problem is that the system need to suck in air when the power fails, so i though of the following.

Is it possible to a normal air tubing (like you use on an air stone or to inject co2, but add a (air) 1 check valve to it? This check valve would be added in reverse, so that water can't "pump out" but air can be "sucked in", like on the image below.

Is something like this possible?


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## Adragontattoo (Jun 3, 2007)

drill a few holes at the min level you want the water to drain to. 

I.e
waterlevel is here





Drill holes here
Min level is here

That way the syphon is broken if for whatever reason the return is not functioning. Just make sure that you leave enough slack in the sump to account for the contents of the overflow tubing.


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## Grubs (Jul 4, 2007)

It would be easier and safer to just drill a hole in the outlet pipe a few mm just below the water line. When the pump is running the venturi effect may actually suck a little surface water into the stream that is directed downward into the tank in your picture.

When the pump stops the tank will only drain a few mm before air is sucked into the delivery pipe to break the siphon.

see: "Drilled hole in return line breaks siphon" on http://www.melevsreef.com/what_sump.html

edit: snap Adragontattoo


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## Squawkbert (Jan 3, 2007)

This is also a very good idea for canister filter users. Drill a hole a few mm below your water line (how much evap. do you allow, how much water are you willing to have put on the floor in the event of a major failure? - set hole depth accordingly, but not so high that you're constantly cavitating the pump). In the event of a prolonged powre failure, o-ring failure, cat yanks/chews on inlet hose or any other failure, you will only lose a little water before the hole breaks the siphon. To plug said hole during water changes, I use a little blob of poster putty (stuck to rear tank rim the rest of the time).


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## Gilles (Oct 12, 2007)

Well guys, that won't work for me. Take a look at my topic in my sig to see that my plumbing is 100% incorporated in my aquarium background (concrete)


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## Diana K (Dec 20, 2007)

The check valve in my system plugs up occasionally, making it unreliable in case of emergency. 
When I am cleaning the system and notice it draining I can clear it, but if I am not home...
I use intakes at the top of the tank to break the siphon as the tank drains. The sump is sized to hold just that much water.


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