breaking a vacume

[jslaney]

So I will be installing my plumbing tonight and I want to cofirm that the only way to prevent your return line from vacuming half the water out of your tank should your pump fail is to drill a hole at the highest point on your return line. How big should that hole be. I am assuming I want to drill it in a direction such that water does not squirt out the top.

Clear as mud?

Thanks,

Jon.

[Aquattro]

Drill 2. That way when I snail sits on one, the other works...

[mseepman]

Depending on the size of your return line, drill 4 because they can and do plug up. I scrub mine weekly with a toothbrush. Mind you they are only 1/8" holes because my return line is only 5/8's.

[untamed]

Originally Posted by jslaney

So I will be installing my plumbing tonight and I want to cofirm that the only way to prevent your return line from vacuming half the water out of your tank should your pump fail is to drill a hole at the highest point on your return line. How big should that hole be. I am assuming I want to drill it in a direction such that water does not squirt out the top.

Clear as mud?

Thanks,

Jon.

The hole is certainly NOT the "only way". If your returns run over the top of the tank, you can stop siphon by not extending those returns deeply in the tank. My returns only break the surface by about 1 inch, so 1 inch is the maximum siphon.

Of course, there is always using a check valve.

Finally, a siphon break hole doesn't have to be at "the highest point"...it just becomes the point where the water will siphon down to... before it sucks air and breaks the siphon. In the case of my 'fuge, that hole is actually 3/4" below the water line. When I kill the pump, it back siphons 3/4" of water before this hole becomes active.

When the pump is on, water squirts though the hole but underwater so that causes no problem. However, since the hole is underwater it is easily clogged by algae and critters, so I would not recommend this for a main tank.

So...a hole just above the waterline might be the most reliable placement for a siphon break hole.

[mark]

My return comes up into the bottom of the tank then a 90 into the display and sits about 2" below the water line. No siphon breaks to worry about plugging and my sump can easily handle the extra water if I have a power outage.

another solution is to plumb in a (lets say your return line is 1") 1"x1/2"x1" SLPxFNPTxSLP "T" fitting in the middle of your return line that runs horizontially above the water surface. In the threaded FNPT, screw in a locline MNPT adapter fitting and run a length of locline off of it that has a smaller flare nozzle spraying water out at the same level as the surface of the water in your display tank. This will aggitate the water surface for great oxygen exchange, not splash much at all, and break any siphon. because the water flow goes straight through the "T" fitting easily, not much flow will exit the restricted locline that exits the "T" fitting at a 90 degree angle, but enough return water will exit to cause surface aggitation, and its easy to position at the right return height to pretent siphon and excess splashing...
Hope that helps you out.
Ive plumbed hundreds of display tanks, learned a few tricks along the way...

[jslaney]

All really good ideas. I am pretty sure I know what I am going to do now.

One good point mentioned is that if you do put it under water, you might as well put it at the same elevation as your overflow as that is the level it will drain to anyway.

Jon.