Holes in returns to prevent siphon

[kung fu]

I need to drill holes on my returns at the waterline to prevent a siphon effect during power outages, etc.
How large would you recommend these holes should be? (1/8 in., 1/4 in., etc.)?
Thanks!
Peace...

 

[richard rendos]

I only see two problems with drilling holes. If the hole is too small, it will act like a venturi and put lots of microbubbles back in the tank. If it is too big, you will have water shooting out of it.
Just a thought.

 

[uncle fester]

I used something in the neighborhood of 1/16. Make sure to drill the hole so that it is underwater approx 1/8" when tank is full to avoid probs Rendo pointed out.

 

[rockface]

If your drilling PVC then angle the hole down. this way when you do start it back up the water will be going into the tank, and not shooting strait forward across the surface of the water. This will keep water from shooting out until enough water is pumped back into the tank to cover it back up. The first time I drilled the return fitting I shot about 2 gallons of water across the tank, and onto my wall before getting the pump unplugged. Mine is about an 1/8 under the water line when full. Just 1, 1/4 hole.

 

[reeferx]

Why not use a check valve instead of drilling holes in your return line?

<img src="graemlins//confused.gif" border="0" alt="[confused]" />

 

[broomer5]

Yep
I had 1/8" hole drilled at first.
A small piece of caulerpa from the refugium made it's way through return pump and actually "blocked" the 1/8" hole drilled in spraybar, enough to NOT allow for vent/siphon break.
Luckly I saw it.
I've since gone to 1/4" holes, slightly angled down as mentioned. Seems to work well.
Check valves work well too - although they will eventually fail as well. Anything mechanical will fail - although I'm not discounting the use of these check valves. Some also contain metal springs, not all, but some. And again, sometimes they do not always "seat" well over time, can accumulate build up of alage/slime and can allow small leakage past this worn or distorted seating area.
Good point though.

 

[rockface]

I was planning to use a check valve, but was told they can sometimes fail when used with saltwater. The lfs told me this before they sold me a check valve.

 

[richard rendos]

If you get check valves, be sure to get the ones with no metal inside. They make some that have a rubber flap inside that work great and salt water will not harm.

 

[reeferx]

I used mine for over 3 years and never cleaned it. It never failed. But I was being pretty stupid. I should have done it the couple times I broke down my tank to move it. They are designed to come apart pretty easily.
If you get one make sure to follow the recommendations on this thread and make sure it is aquarium approved. I believe the one I put a pic of here is, right click on it and view its properties to get the site I got it from if you want to follow up.