I have an overflow problem someone help me out

I just tested my closed loop system and it works awesome, but theres one problem. When I turn off the power the water continues to drain back into the sump via the return pipes and floods the sump. I drilled a hole in both return pipes. In theory this wil break the siphon and stop the overflow right?

 

Yes it should stop the overflow. How far below the water level in the display tank did you drill your hole in the return pipe???

 

A closed loop has nothing to do with a sump and is exactly what its says, closed. In a closed loop you take water from the display, through a pump and back to the display always in a closed system and never exposed to atmosphere so the level of the returns is not a factor, there is nothing to drain back to.
In my case I have a 1" bulkhead in the back center of my 100G display with a strainer fitting on it. It goes into a ball valve for isolation then through a Ocean Runner 3500 pump, on to an Oceans Motions Squirt two way and back to the two upper back corners of the display where it exits with Loc Line. It does not matter if the power goes off since it is "closed".

Are you actually referring to your sump return line? If so this is not a closed loop and the returns must be close to the surface so once the display level drops sightly the returns are exposed to atmosphere and break suction. The higher the better. On my returns the level can drop 3/4" in the display and they break suction so I get about 3.8 gallons back in my sump before the backflow quits.

I never ever trust drilled holes or a check valve as both require maintenance and still fail on a regular basis. Air gaps cannot fail and are the best method of backflow prevention there is.

 

The holes are dilled in the back of the tank. The tank is a 125 with two overflows. Each overflow has a stand pipe attacked to the bulk heads. The return has a hole drilled right next to the overflow. So each overflow has one return and one overflow if that make since. The return comes over the overflow box and goes below the surface of the water about 5 inches. So my two returns are 5 inches below the surface. It was creating a siphon and returning the water to the sump when unplugged the pump. I then drilled a hole in each return pipe to break the siphon.

 

I see what you are saying. My return pipes are submerged about 5 inches from the surface, what I'm trying to ask is can i just drill a hole in them at the top or do I need to put them closer to the surface? I just saw the last part of your post, I will move the returns closer to the surface thanks for the replies and the advice, I really appreciate it.

 

I wouldn't rely on drilled holes, all it takes is a piece of food, algae, a small snail of fish, an anemone or who know what to defeat them.

You are talking about your returns and not a closed loop.

Does the return have a 90 degree elbow where it travels over the overflow box? If so I would attach LocLine to the elbow and bend it so its just slightly below the surface and is exposed with just a slight drop in surface elevation in a power outage. Then you always maintain at least that much freeboard or spare room in your sump at all times.

Take a look at the picture of mine here and you can see where the return goes over the overflow box then exits into two LocLines which are just barely in the water. They break suction at almost exactly the same time as the teeth on the overflow box so I drop 3/4".



This picture was when i was first constructing the canopy so the lights are sitting on boards over the tank temporarily but it gives you another view.

 

Yeah, thats exactly how my setup is. The problem is i'm using pvc instead of loc line, I guess I will just have to get the loc line to fix the problem. Do you know where I can get 1" loc line? I just looked at bulk reef supply, the biggest they carry is 3/4"

 

marine depot or ebay

 

I think 3/4" is the largest.
ModularHose.com - Loc-Line Modular Hose System

 

Just drill a hole in each pipe just below the surface of the water to break the siphon during a power outage. Even with this, siphon overflows are very risky.