Check valves on anti-syphon holes

[M.E.Milz]

I am adding a large return that will come up the back of the tank and then split into several separate returns before exiting inside the tank at mid-water level. I plan to drill anti-syphon holes in each of the separate returns just above the water line.

As a backup, I was going to add another anti-syphon hole in the top of the manifold that splits the single return into the separate returns. Since the manifold is behind the tank, I will need to run some air-line tubing from the hole to somewhere above the tank (or the sump) so that the water being pumped out of the tubing will end up in the tank and not on the floor. But what if I added a check-valve to this tubing so that water will not be pumped out during normal operation, but will allow air to enter (and break the syphon) should the pump get shut off? Maybe I could even use a relatively large check-valve (compared to the size of teh airline tubing) to ensure that the syphon will be broken quickly? Any thoughts?

Mike

 

[Anonymous]

hi.
There should be no need for a ASH on the manifold if there are already one ASH on the each of the outputs. As long as any single one of the outputs' ASH worked, all the other outputs' siphon will broke, including the one in the manifold.

If you have problem visualize the domino siphon breaks, try to see how you going to start a siphon if any of the outputs' ASH is open... impossible unless you have something that can suck very fast.

 

[M.E.Milz]

ALL of my return lines exit under the water surface (many inches below, in most cases). Thus, I want to break the syphon as quickly as possible so as to avoid any possibility that the sump will overflow.

But my experience has been that delays in breaking the syphon can occur if the ASH becomes restricted in size and/or the syphoning action is large. Therefore, I want to use a larger ASH and/or mulitple ASH's. But either option means more water being diverted from the main return lines and out through the ASH's. I figure that by using a checkvalve, I can use a large, optimally placed ASH (e.g., at the highest point of the return) that will break at the first instance of pump shut-off. Moreover, since water will not pass through this ASH, then it should not get clogged with coraline algae over time (like my standard ASH's tend to do). On the otherhand, I do not want to rely solely on a single ASH with a single checkvalve that might fail, which really would be a dissater. Maybe mulitple large ASH's, each with its own checkvalve?

 

[Anonymous]

hi.
You have several options, as you already know. For a ASH check valve, make sure you get one that normally open, without any "cracking" pressure (the amount of force/area needed to open, hence crack, the valve). Sometimes, I feel that a swing check valve on the pump's return maybe a better alternative than ASH setup. Did you consider that already?

 

[Iron]

IMO if you have alot of returns low in the water just add one return at the top of the tank. even if it's reduced to a 1/2 " flex nozzel. As long as it's connected to the main it will break first and won't clog. If thats not an option I would use an anit siphen at the highest point and include a check valve. A clear good quality one you can clean. This way you don't depend on one or the other. They can both fail IME. Whatever you do back up your back up. When you have returns deep into the take it's scary. But IME anti siphen holes have failed more x's than my check. But I use both