Where to drill hole on the return line

[cfide]

I am going to drill a hole on the return line to prevent back-siphoning in case of power outage. Where do people usually drill this hole? Below the water level, above the water level?


____c___
overlflow | _____ |
| | | |b | |
-| |----------------------- | |--|| | |
| | _ | |a ||
___| ||
|| tank

"a" will be below water level and overflow intake, "b" will be above water level and above overflow intake, "c" will be on top. I think "b" and "c" will create a small stream of water which will end up creating bubbles.

 

[phishphood]

can't really tell from your pic, but I like to drill below the water line, usually on the side of it (so water comes out horizontally, and not straight up, potentially breaking the surface). I don't think it really matters where it is in relation to the overflow height, but it's more a matter of how much room you have in your sump.

 

[pixelpixi]

I would drill it about a half inch below the water line. Don't go much below that because your tank is going to drain to that level when the pump shuts off.

 

[Tumbleweed]

[quote author=pixelpixi link=topic=4858.msg59261#msg59261 date=1224198617]
I would drill it about a half inch below the water line. Don't go much below that because your tank is going to drain to that level when the pump shuts off.

[/quote]
This is what I did. But I drilled 2 holes on opposite sides of the line. This is just in case 1 hole gets clogged of covers by a snail that wanted a foot massage.