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

[Doug]

Originally Posted by gregzz4

Should I use a union check valve or not?
I don't want to drill my lines.
What's your experience?

Whats the matter with his response?

I have done my tanks that way for 40yrs. Never have I ever used a check valve. My returns have just been under the surface, with the sump holding any back flow.

I also drilled a 1/8th. in. hole for back up but as mentioned, my systems would be fine without.

I liked to drill them om an upwards angle so the water sprayed straight down. Also on the backside, where the piping came over the top. I found snails could not bother it as much when between the pipe and the glass with not much room.

Only snail problem I have had was one the cover the hole partially and the water squirted in the air. That was corrected by the above angle and placement of the holes.

Having the return just below the water line is still the best solution as was said. If its under far enough that back flow will flood the sump, {for whatever reason I,m not sure},then a check valve is the only solution. Although many have run them with great success, I have read many stories of floods from their failure.

[fishytime]

most check valve failures are due to the seals getting schmengy....I always recommend that people buy two and swap them out for cleaning......that and make sure that your sump can handle any back siphoning that may happen in a "worse case" scenario

[Doug]

Originally Posted by fishytime

most check valve failures are due to the seals getting schmengy....I always recommend that people buy two and swap them out for cleaning......that and make sure that your sump can handle any back siphoning that may happen in a "worse case" scenario

Good advice.

[Delphinus]

I've run both anti siphon holes and check valves on tanks in the past. Both are methods equally prone to failure and there will always be a chance they fail one time when you're unprepared. Maintenance will reduce the risk but not eliminate it completely.

I prefer the KISS principle.. On my tanks I run now I keep enough space in my sump to handle the backflow. The higher the output nozzles the less backflow volume you need to account for. Plus, having output nozzles near the surface has the added advantage keeps better surface agitation.

[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.

[reefme]

+1 to Myka. Very well explained.

[sphelps]

I agree with Myka, the need for siphon breaks or check valves is a result from bad design. I think the majority of experienced people will agree you shouldn't rely on such things. However you may want to add them to prevent full back back flow all the time but your system should still be able to handle the back flow if the breaks or valve fail. If this were the case check valves would be a better option than break holes as they require more maintenance being that they are often plagued with algae growth.

[fishytime]

In my case it's not bad design..... I do my water changes by siphoning from the display most of the time.... Siphon break holes and check valves help keep more water in the display so I can siphon out more crap....

[sphelps]

Originally Posted by fishytime

In my case it's not bad design..... I do my water changes by siphoning from the display most of the time.... Siphon break holes and check valves help keep more water in the display so I can siphon out more crap....

Agreed provided they aren't actually needed.

[Proteus]

Originally Posted by Myka

(who fills their sumps more than 60% anyway??

I do lol. But only because my last baffle is too high so if I keep water level to low I end up with bubbles in dt. But my sump still holds any flowback