How to prevent airlock in DIY overflow?

[jschall]

I need a 100% foolproof overflow. Drilling isn't going to happen at this point, I probably should've had the tank drilled when I got it. Anyway, I intend to use a variant of the following design:

Going to use that but with 2 siphons instead of 1. I've already built and tested it with one siphon. I'll take a picture when I have the final product.

Anything less than foolproof and the parents won't let me drill the wall for the constant automatic water changer. The issue is how to keep the siphons from accumulating bubbles over time (the flow rate is going to be 0.25 gph per siphon.)

An idea I had was to use a tom aqua lifter pump with a check valve to constantly pump water or air or whatever accumulates in the top of the siphon out and back into the tank. The questions that instantly come to mind are: is the tom aqua lifter quiet, and do the check valves keep a perfect seal? I'd probably use several check valves in series.

If you have a good alternative to what I've described, please post it!

 

[jschall]

and what's the best check valve to buy?

 

[jschall]

I just realized the check valve isn't that important as long as the outlet of the aqua lifter pump is under water. Will still use a check valve anyway.

Here's a picture of my overflow, with the plans for the aqualifter-based self priming system:

It's built with 1/2" pvc, but it only has to handle 0.5 - 2.0 gph max.

Here's how I'm going to drip the new water in:

The 1/4" tube will come in through the wall.

 

[brianhellno]

I had a PVC overflow and this is how I would purge it from air. I never had a check valve I just sucked the air out with a small hose I had placed in it and then just pulled it out. Anyways whenever I noticed the flow starting to slow down I had a ball valve put right before the sump. I would shut the pump off and let everything equalize and then I'd close the ball valve. Then I'd dump a bunch of water in the siphon break and cap it off. Then I'd start the pump to raise the water level in the tank a little higher than desired and then I'd quickly open the ball valve. From what I gather the water that quickly rushed in and with the siphon break capped it created a siphon that sucked all the bubbles out. Then I'd just slowly remove the cap until everything equalized and I had full flow. Sometimes I would have to extend the siphon break with another pipe and fill the one with water to add more water for pressure but it's worked every time I've used it. Hopefully this helped I'm not sure I explained it as well as I could let me know what you think.