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I want to connect tanks with a U siphon

My sump tank is at ground level and there is roughly 600 gph passing through it. That water is pumped directly back into the FT. Because the water is constantly pumped out and the 4 bell siphons regularly drain into the tank, the level in the sump varies between 8" to 16".

I want to build a DWC across the walkway, 2 feet away. The DWC will hold about 600 gallons and I want to pump that water directly back up into the FT. The water level in the DWC should average about 12 inches. I want to supply the clean water from the sump tank to the DWC using a U siphon.

My theory, using the understanding that water seeks it's own level, is to form a U configuration between the two tanks. That configuration would be filled with water. With NO air in the plumbing between the tanks, the water should always seek a constant level in both tanks. With the pump in the DWC returning the water to the FT, at a rate of 600 gph, the water should pass from the sump to replace what has been pumped out of the DWC.

Here is a pic of what we currently have. The DWC will be along side what you see, with a 2' walkway between. The 1st tank is the sump and the last is the FT.

Your thoughts...

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Replies to This Discussion

Permalink Reply by TCLynx on June 29, 2012 at 10:23am

How high will the DWC tank be?

There are drawbacks to using a Water Bridge or U siphon to equalize level between two tanks, they tend to get gas and break so you have to regularly make sure they are fully primed or have no air bubbles building up in them.

It seems to me it would be much easier to plumb an actual drain line between the sump and the DWC bed below the normal low water line instead of trusting a Water bridge. With an actual drain line you could have the plumbing run on the ground or even in the ground to leave a clear pathway while a water bridge would normally be installed straight across between the tops of the two tanks effectively blocking your pathway. If you were to make it into a Double U in order to keep the pathway clear, it will become even harder to keep it primed since you will have two separate high spots to remove air from.

2" or better yet 3" uniseals are not that $ and having a normal drain instead of a water bridge that needs to be checked all the time seems like an easy choice to me.

Permalink Reply by Chris Carr on June 29, 2012 at 11:34pm

Looks like there is already a 2inch plumbed with a uniseal and capped off no?

I love the idea of using a bridge, but TC makes good points about what can go wrong. If there was a scenario where one had to use a bridge, would adding 2 90degree elbows on each end help with keeping air out? My guess would be that the air that does get in, isn't bubbling right up the inlet/outlet as much as it is leaking joints and gas bubbles forming on the inside of piping surface. Maybe not?

Permalink Reply by TCLynx on June 30, 2012 at 7:04am

Yes, making a "trap" at the bottom inside both tanks with elbows does help keep water from bubbling up into the U bend and is what I did for no holes overflows as well but it is also true that gas can escape and form bubbles inside the bridge and also if the joints are not cemented properly air can leak in, since it is a siphon there is a bit of a vacuum in it and it will be trying to suck air in to let the water down.