Opinions appreciated: check valve vs anti-siphon holes in overflow returns

reefwars · #1 04-08-2012, 04:42 PM

Quote:

Originally Posted by Myka

I do this too, but in my case, after siphoning 10 gallons out I turn the return pump on the empty the sump so I can remove another 5 gallons from the display without the corals being out of the water very long.

I have an "emergency" drain for just that purpose.

this is what i do too

Quote:

Originally Posted by Myka

This topic really irks me. It is beyond my realm of mental capability to understand why someone would design a system that could possibly allow an overflow during a power outage.

Personally, I have no use for a check valve. I think they are a waste of money. I would rather design my sump to accommodate the back flow (who fills their sumps more than 60% anyway??), and design the return plumbing in a way that only an inch or two of water will back flow. To me, relying on a check valve or anti-siphon holes to keep my floors dry is absurd. If the system is designed in a way that the sump won't overflow regardless, then it makes the check valve and anti-siphon holes completely superfluous.

When designing the system, measure from the running water line to the top of the opening of your return line (where the siphon will break). Use an online volume calculator to figure out how many gallons will back siphon. Make sure you include any other volumes of water that may siphon (like a compartment/overflow box that has some silly design). Then add 25% for safety. Then measure from the water line in the sump to 1/2" below the top of your sump. Figure out that volume. If the available space in the sump is more than the back flow volume you're good to go. If the available volume in the sump is less than the back flow volume you need to redesign to make space for the volume or to reduce the volume backsiphoning, and I don't mean to using gadgets like check valves! Redesign by using standpipes, baffles or such in the overflow boxes, or by raising the return opening to make the siphon break higher.

If all else fails, you just can't seem to figure this out then fill your tank up outside with the hose and do a freshwater test run.

agreed, since most return pumps arnt the main source of flow most just use them for surface agitation, i like that when i need to the high loc lines are good to point towards my frag shelf:P

Proteus · #2 04-08-2012, 04:47 PM

+1 on emergency drain

I have 2 overflow with with one emergency.

bignose · #3 04-08-2012, 05:30 PM

Everything that myka said makes sense. I don't use check valves on my system but I drilled holes in my returns and I make sure that they are cleaned every so often to prevent plugging.