Siphon Breaks?

[TriniStylez]

I always hear about drilling holes for siphon break if the power goes out...Where are these drilled? Pics would be great! Thanks.

[cannarella]

I don't have a pic, but it is above or right at the water line on the return so if the power fails or the pump it turned off air can enter to prevent it from being syphoned down.

[TriniStylez]

Ok, so just a small hole on the return at the waterline...What size hole are we talking?

What if your return outlet is just above the waterline anyways?

[cannarella]

Yea on my All Glass Mega Flow kit the return comes up and hits a 90 deg elbow and in the insid corner there is like a 1/8" hole drilled so the water shoots down into the overflow.

[latazyo]

when I drilled mine above the waterline it sucked air in like a skimmer and put bubbles in the tank

I had to redo it slightly under the waterline

[TriniStylez]

Originally posted by cannarella
Yea on my All Glass Mega Flow kit the return comes up and hits a 90 deg elbow and in the insid corner there is like a 1/8" hole drilled so the water shoots down into the overflow.

Ok, my return is going to go over the back and have a 90 deg elbow and a 45. Does this change where or how I drill the hole? Sorry Im a bit confused still on where to drill it.

[TK3]

Originally posted by latazyo
when I drilled mine above the waterline it sucked air in like a skimmer and put bubbles in the tank

I had to redo it slightly under the waterline

Yeah always under the water line. Allow for evap if you're not using auto-top off, and go about an inch (basically use the amount of water your sump can handle before it gets too close to the top, as a determining factor for depth).

[TriniStylez]

Ok...For some reason I still just do not "get" this. How is water going to siphon back from the display into the sump through the return? Besides whatever water is already in the return plumbing and was on its way back to the tank. I have my return planned to be returning water right at the surface. It is not "underwater", does this make a difference?

[IPT]

If it is not under water you should be OK. Think about it this way. When you siphon a tank for a water change you suck water thru a tube until gravity takes over. The water will then drain from your tank to a lower level until it is even all on it's own (with a little help from Gravity) . You can "break"the siphon by pulling the draining end of the tube out from the water. It "breaks" because air enters and then there is not enough water flowing down the tube to create the suction needed.

Your return line is pushing water from your sump up into your tank. Your return (sump to main tank) is basically a siphon tube. The difference is usually a pump forces water back up into the tank overpowering graivty. If that pump shuts off, and your return is below the water line, you now have a siphon to drain your tank. With the hole drilled (higher than the actual opening of the return line exit) it will suck air and break the siphon earlier. If your reutrn is deep into the tank or you have a small sump you want that or else your looking at a flood. Otherwise it'll drain the tank to the level of the opening on the return before it sucks air and brakes the siphon. If your sump is big or you return not far below the water line it may not make a difference. Make sense now?

[latazyo]

I wouldnt go an inch, I dont think most sumps can handle that much water

I woudl do it about 1/4" below the water surface on your return line

I have 4 submerged returns and only drilled one of them and it breaks the siphon everytime

this isn't an "in case power goes out" thing...this is an "everytime you turn your return pump off for whatever reason" thing

[Wrassemeister]

you can also out a check valve onyour return as an extra precautionary factor...

[RandyStacyE]

I never drilled a siphon break in my return line.

I just keep my return line just above the water level so I never have to worry about it.

Some people rely on their return line for water movement/circulation (or for whatever reason) and deeply submerge their return line and have it pointed in the direction they want to shoot the water.

In such a case they MUST have a siphon break or else the display tank WILL back siphon, overflow their sump and drain the display tank down to the level of the opening in their return line.

[cannarella]

Originally posted by Wrassemeister
you can also out a check valve onyour return as an extra precautionary factor...

You could, but I have always heard that eventually all check valves will fail in SW.

[Wrassemeister]

Only way they will fail is if they get clogged. They have clear pvc check valves that you can see through and know if it needs cleaning or not. Again, its just a precautionary measure in addition to the syphon breaks and you can't go wrong with spending 15 bux when you are talking about possibly flooding your home or your neighbors home if you live in a building.

[cannarella]

True true

[AZDesertRat]

Check valves are mechanical devices and will fail, guaranteed. All it takes is a singlegrain of sand, a small snail, a flake or piece of food, algae or slime, anything that prevents the flapper from contacting the seat. If you experience a power outage and are not home even a slow backsiphonage will overflow the sump given time. You could have cleane or serviced it 10 minutes ago but that will never prevent a snail from lodging in it.
The only surefire method of backflow or backsiphonage prevention is an air gap period. Not drilred holes which can and will fail also for the same reasons as thecheck valve. With the returns either above the watres surface or even below the surface as I have mine, once the water level drops below the returns outlet, its impossible for water to continue flowing to the sump. I know that one inch of water in my display is equal to 4.6 gallons so I always maintain at least that amount at a minimum in my sump at all times, actually I keep about 8 gallons of freeboard even when the sump is at its fullest and I can sleep peacefully at night with no fears of a flood.