Return Line Siphon Break

[ragin_cajun]

So....I'm gonna put one on a return line (really 2 cause I have 2 return lines, but let's keep this simple and talk about 1 return line).

I have a 1.5 inch PVC return line. It's black ABS. I'd like to drill a hole, thread it, and put in some kinda threaded poly line type fitting. Then I can just move that poly line wherever I want above the water line in the tank, or maybe even just run it back into the sump somewhere, for maximum silence.

Has anybody ever done this? What's a great threaded fitting to use for the hole I drill in the ABS pipe. What size threads are small enough for the ABS pipe hole, but big enough to give a very solid and tight seal against water leakage, etc?

And could I just do this in the sump, instead of in the display? Seems like to me it doesn't matter where I drill the return line, so long as the hole lets air into the line when the pump shuts off?

How much air needs to get into the return line to break the siphon? would a 1/4 inch hole let enough in?

 

[millerkid519]

I would use a 90 degree 1/8 inch npt to 1/4 inch barb fitting.
You can try running it down to the sump I think it would work fine

 

[ragin_cajun]

1/8 inch NPT? So, drill the PVC, tap it, and screw in the fitting? That's big enough to break siphon on 1.5 inch return line?

 

[Fish Tank Travis]

My returns are 3/4" with 1" tubing going up to them and I drilled a 3/32" hole on each side of the elbow at a downward angle, just below the water line. It's completely silent and breaks the siphon every time.

You can't drill the hole in the line in the sump because that will still keep the siphon inside the tank and continue to drain it. The hole has to be inside the tank and has to be near or above the normal water line so it can allow air into the line as soon as or very soon after the pumps are shut off.

My opinion, don't over complicate the idea of a siphon break and just drill a small hole, or several small holes, in the topmost part of your return inside your tank, just about 1/4" below the water line. Drill it at a downward angle so it shoots down when restarting the pumps. Simple, silent and done!

 

[ragin_cajun]

I can't drill it like you describe. Here's some pics....I'm thinking drill into that short vertical run of black pipe before it turns back down into the overflow box to go down to the sump?

 

[ragin_cajun]

pics are right here

 

[millerkid519]

1/8 inch NPT? So, drill the PVC, tap it, and screw in the fitting? That's big enough to break siphon on 1.5 inch return line?

Yes 1/8 inch npt will be big enough

 

[Fish Tank Travis]

pics are right here

View attachment 1254552

View attachment 1254553

View attachment 1254554

It looks like the best spot for a siphon break hole is just under the water line, right about where the white threaded fitting is, or just a hair above it. If you can't get to this spot during a water change then drilling a break hole in one of the elbows above the tank and installing a small npt fitting, 1/8", and running some sort of line into the tank so that the outlet is just under the water line will work just as well. You could use loc line, if they make it that small, or some small vinyl tubing with a hose barb fitting. It must go back into the main tank though.

 

[jaws7777]

Not being a wise guy, whats the benefit of having the line run ino the sump ?

 

[DN328]

I can't drill it like you describe.

This would be the best approach. But can you elaborate why you couldn't drill. Is it accessibility and/or bulkhead that extends below the tank water level?