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Old 09/19/2018, 10:21 AM   #1
cvrle1
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How to prevent backflow in drilled tanks?

Hello everyone,

Was doing some reading last night, but couldnt find good info on how to prevent backflow of water from the return piping in a drilled tank. Consensus is not to use check valves, and similar, as they will clog up and not work. For folks that are using over the tank returns, it is easy to control by drilling a hole that would break siphon. How do you break siphon for tank with drilled returns though?

Tried finding pics and such, but wasnt ale to get any conclusive answers.

Thanks for the help.


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Old 09/19/2018, 10:31 AM   #2
homer1475
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My tank has drilled in returns, and I use locline on them. I simply place the nozzles high up so the drain back is minimal before they break siphon. I use to use siphon break holes, but they get clogged up pretty quickly.



My returns being up high I only rely on them to break the surface tension not for any kind of flow.


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Old 09/19/2018, 10:32 AM   #3
Rover88
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I believe in the tanks where that would be an issue, you either drill a small hole on the top side of the return equipment, or they are mounted so high in the tank they won't siphon much.

Even with drilled returns there is /something/ protruding into the tank that the water is directed through, and you can put a siphon-break in it. Otherwise, you just need to be sure that the sump can accommodate the backflow of whatever amount of water it will draw down.

I have an over the top style of return, so maybe someone that owns a drilled return can better clarify.


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Old 09/19/2018, 10:38 AM   #4
cvrle1
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Quote:
Originally Posted by homer1475 View Post
My tank has drilled in returns, and I use locline on them. I simply place the nozzles high up so the drain back is minimal before they break siphon. I use to use siphon break holes, but they get clogged up pretty quickly.

My returns being up high I only rely on them to break the surface tension not for any kind of flow.
Thanks very much for this info. with your returns being high, and you using them only for surface tension, do you find you get more salt creep or water splashing around? I guess this would depend on return pump, as if it is too powerful, it will cause these issues. Am I right in this assumption?


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Old 09/19/2018, 10:57 AM   #5
Darth_Tater
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My preferred method is to use 90 degree elbows to get the return as close to the top of the water line as I can. Same principle as using the locline, but I'd argue it increases head pressure on the pump less. Locline seems to be designed to create faster flow by increasing pressure, but at the cost of decreased water volume.

If you do decide to just drill a hole as a siphon break (I use this method on one tank where my return line goes over the top of the back), make sure it's a decent sized one. I ended up enlarging mine because it kept getting clogged. Haven't had a problem since I made it bigger (I think I went up to 1/4"). Also make sure the siphon break hole is slightly below the water line as water does come out of it when the pump is on.


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Old 09/19/2018, 02:31 PM   #6
homer1475
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My returns are still below the water line, they just don't back siphon a ton. With them being below the water line and pointed up, they just ripple the surface. I get no out of the normal salt creep.



They are just above the lowest level of the teeth on my wier. So they only drain back as much as my overflow will empty the main tank.


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Old 09/19/2018, 03:26 PM   #7
James77
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I use locline to get it as close to the surface as possible.

I also use a check valve run in reverse. It is basically a second outlet I run that is totally above the water line, but pointed down into the tank. But I reverse it so water is blocked, no water ever comes out. But if power is killed, air is immediately introduced to the return line breaking the siphon.

I got the idea from:
https://www.reef2rainforest.com/2014...e-check-valve/

Mine is not as obvious as the above, it is simply a 1/2" black PVC pipe and elbow that comes out over the top of the tank.


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Old 09/23/2018, 11:17 AM   #8
zachfishman
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Quote:
Originally Posted by James77 View Post
I use locline to get it as close to the surface as possible.

I also use a check valve run in reverse. It is basically a second outlet I run that is totally above the water line, but pointed down into the tank. But I reverse it so water is blocked, no water ever comes out. But if power is killed, air is immediately introduced to the return line breaking the siphon.

I got the idea from:
https://www.reef2rainforest.com/2014...e-check-valve/

Mine is not as obvious as the above, it is simply a 1/2" black PVC pipe and elbow that comes out over the top of the tank.
This is really clever!


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