Siphon Failed

[DirkW]

I've got a 29G display tank and two 10G breeder tanks above it. A canister filter pumps water to the upper level, which siphons from one tank to the next, and an overflow box returns the water to the display tank. The siphon failed, causing one of the 10G tanks to overflow, and leaving about 2" of water in my display tank, dumping more than 25G on my floor, and ruining a powerhead. I'm trying to figure out what happened to my siphon.

The siphon is made of 1.5" PVC with a 180-degree elbow (a p-trap, used for a sink drain). I drilled a small hole in the elbow, and attached an airline fitting sealed with silicon. Attached to either side of the elbow are two pipes about 12" each. The joints between the pipes and elbow are sealed with silicon. I attached airline and sucked out the trapped air to get the siphon started. The siphon worked for about a week and showed no signs of slowing down before it failed. Apparently, air must of somehow leaked back into the siphon. The airline was still half full of water, so the clamp on the airline seems OK. Any ideas what went wrong?

 

[karlp]

First sorry to hear about your mess!

Silicon sealant and flexible hose does not good sealed joints make, so I would suspect those as a starter. take the syphon hose out, block up one end with your hand or a stop of some sort. Put washing up liquid around the joints and blow into the other end to pressurise it. If you've got soap bubbles forming, then there's your leak. Also check that the clamp is definitely not allowing any air back in. The fact that it took a week to show, could indicate that it was a small leak that took a week to accumulate enough air to break the syphon.

I would suggest either: - replacing the DIY sealed joints with proper compression joints (e.g, it all goes together air tight without the need for sealant or drilling the pipe). or..

Go for a simpler setup. Like under gravel filters or internal foam filters in the 10g tanks and just use the external for the show tank.

 

[DirkW]

Thanks for the reply! To evacuate the air in the siphon, I attached an airline fitting designed to hook up two sections of hose. That is the piece that I attached with silicon, not the hose itself.

That's a good idea for checking for leaks. I suspect the leak may be where the pipe meets the elbow.

I guess I'll hold off asking my wife about a new saltwater tank for a couple months.