Backsiphoning

How do i prevent this? i have a 5.5 gallon sump so i cant really have a fill max line. I already glued the pvc structure and its in place for the return and theres still a lot of backsiphoning when the tank turns off. Any suggestions on how to prevent this? does drilling a hole right above the water surface in the return pvc work? ill do anything but its pretty hard to un-glue pvc so i can move the return higher up in the tank.

 

Drilling a hole will work. Once it starts to back siphon, the air from the hole will be pulled in and it will break the siphon.

There are also PVC check valves that prevent the water from back siphoning.

 

How big of a hole? more than one? and i know, ive heard of those check valves but its too late to add one. Wish i would have thought of that earlier

 

I'm pretty sure if you use a small enough hole, the water returning to the tank won't spray out of it.

What type of return do you have? I'd say the hole should be dependent on the size of the return. If its a small return, a small hole should do.

 

The check valves are not a good choice in saltwater. They get clogged in a very short time with salt and calcium and will fail to work when you need it
Just drill a hole slightly UNDER the water level. 1/8" hole should be plenty.

 

awesome, sounds good. Im using 3/4 inch return. does that change anything?

 

A couple of 1/4" holes just below the water line will do the trick. I always use more than one just in case a snail happens to be feasting over the hole when the power is cut. If you drill the hole above the water line you'll draw air into the the pipe by the venturi effect. You need to make sure your sump has some room for water that will come through the overflow after the pump stops.

 

oh i know that i just dont have enough room down there for all the water that would have been backsiphoned

 

+ 1 I would stay definatly stay away from a check valve in the system. Its not if it will fail, its when.

 

I haven't had any problems with check valves yet.. I have a few systems that have the display tank on a higher floor, and then sump/fuge and everything in the basement. These tanks have PVC check valves, and I know they have been working for past year or so.

Everytime I shut the systems down, they work... You got me worried now though.