Sump Overflow Question

[Cliff]

I’m helping a friend set-up her 125 gallon SW tank. It’s pretty cool as we are learning together. We are both in the process of setting our first SW tanks.

Her tank is not drilled, nor does she want it drilled, but she is planning on a 55 gallon sump. She has asked me for some help so I’ve been looking into overflow designs that we could use on her tank. She would like a overflow that (when the power went out) would automatically start working again once the power came back on. I’ve never set-up a overflow like this so its all new to me. I found a few designs as well as a view videos on how they work. They seam simple enough to put together, but I’m still not clear on how you get it going.

How would you prime a system like this to get it started ?

Also I’ve noticed that some have a small air vent at the top of the loop on the outside of the tank and other do not. Would you need a small vent hole ?

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[WhiteDevil]

Youd need a lift pump I think to kick it back on when the power comes back on.

I bought an overflow and didnt make one when i set mine up so unsure on DIY but I still think a lift pump is needed.

[Michael Milligan]

White Devil: I'm pretty sure what you're talking about is a siphon drain of some kind. See this page about how this works and how.

You might also see something familiar in the design. ;) Looks just like mine too! lol

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[Crispy]

White Devil: I'm pretty sure what you're talking about is a siphon drain of some kind. See this page about how this works and how.


a siphon drain is not good. it will not stay primed in case of a power outage. it needs the air vent incase of power failure so it will stop draining.

you prime the DIY overflow by sucking all the air out of that vent and then popping in the air-valve.

Pic #2 is the best design and will stay primed and not flood your sump.

[WhiteDevil]

this is what i am talking about.

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[Sarkazmo]

I built these before and they work great and hold a siphon. Both designs in the OP's message are essentially the same with exception to the one way valve which is used in priming and is only needed in priming. Some people add a lift pump to this point so that a vacuum is always drawn in that area of the pipe so that the siphon won't break. These lift pumps then start pulling water from the bend and that water's dumped either into the overflow vent or back into the tank.

If you are going to build one of these I recommend that you make the pipe that actually lifts the water from the tank as deep as possible. So those elbows in the second pic or the bottom of the over flow in the first pic should be on the bottom of the tank (and the pickup inside the overflow should be about 1" from the bottom of the overflow.) This will increase the water pressure pushing into the overflow pickup or at the bottom of the bends for the second design. This will give you a higher flow rate out of the tank. It also has the added benefit of it being less likely to stall or lose vacuum. Stay away from small diameter pipe as well. Use nothing less than 3/4" and ideally at least an inch in pipe diameter or more but that's also dependent on what size tank and the flow desired as there's a maximum gravity flow rate for a given diameter of pipe.

The safest way would be to use a lift pump, but it's not absolutely required.

Sark

[Cliff]

Thanks for all the feedback guys.

This helps a lot.

[Michael Milligan]

Stay away from small diameter pipe as well. Use nothing less than 3/4" and ideally at least an inch in pipe diameter or more but that's also dependent on what size tank and the flow desired as there's a maximum gravity flow rate for a given diameter of pipe.

Sark

Min 1"

I bought an expensive, Italian Marineland return pump for my tank. I built the overflow from 3/4" because it interfaces with the 1" vinyl tube that I also bought. Bad move. :( The overflow is SO much slower than my pump that I keep the ball valve on my return mostly closed. The pump has the guts to stir up my whole 80 gal tank but is held back on account of my small over flow. :(

I just have to go to HD and make another. I'll just use this 3/4" overflow to feed my planed octopus tank water from the main tank... and get a smaller return pump to the main tank. And cover the pipes with screen or the octo will squish into the main tank!