Anti Syphon hole problem

[Abissus]

I am trying to setup a new tank and am testing it with tap water.

For some reason the anti-syphon hole is not working very well. The hole (a little less than 1/4" diameter) is slowing down the water flow but it is not enough to stop it

I drilled another hole and still no good. Then I tried connect the 2 holes (so the opening is almost 3 times the size the original hole, but still no good. I am going to try drilling more holes and keep trying.

Does it make sense to need such a big hole to break the syphon? Is it better to have a big hole or multiple smaller holes? Am I doing something wrong?

To give you more details, the hole is drilled on the pump side of the upside-down "U" tube going to the spray bar.

Thanks a bunch.

 

[lizardarm]

i'm not entirely sure what your set up is based on the description, when you say "upside down u-tube" are you talking about an overflow box?

i can say that it is generally better to have more than one suction break hole, in case a snail, anemone, xenia, etc. decides to park on it at the worst possible time.

 

[Angelscrx]

"To give you more details, the hole is drilled on the pump side of the upside-down "U" tube going to the spray bar."

If I understand this correctly the hole is not inside the tank? U tube usually refers to the over flow box. The return from the sump is usally elbowed over the tank with the siphon break hole close to the top of the water inside the tank. If the pump shuts off and the water starts to drain into the sump, once the water level reaches the siphon break hole it will suck air and the break the siphon. You have to be careful how low you drill it because the lower it is the more water it will drain into the sump or fuge. HTH?

 

[lizardarm]

that's the way it should be.
how far below the water line is the outlet? on my tank, plumbing is all 3/4" thin wall pvc. the outlets are 90 degree elbows, i didn't drill syphon holes in them because they are adjusted pretty close to the top of the water. this is another option.