1" is kinda small. You either have a leak, or you need to bump it up to 1.5".
I have no leak, and the size is perfect for the flow I want. It ran for a year with zero problems.
You may be sucking air around the check valve tube, or the check valve is bad so it looses the prime.
I never even thought about the check valve, I'll take a look.
QUOTE=Hoppy;2858114]When I used one of those I found that tiny air bubbles would collect in the outside "U" (upside down). As enough of those collected there they would finally be one big bubble big enough to break the siphon. I then had to restart it by connecting a water hose to the drain line outdoors, plugging the vertical vent pipe, then running a heavy flow of water to fill the whole thing with water again. Turn off the water, take the cap off the vertical drain, and it would start siphoning again. This happened about once a year. Mine was made of 1/2" CPVC pipe.
I believe this works much better if the outside "U" (upside down) is at the same height as the opening in the vertical drain pipe in the tank, or just slightly above it. Otherwise you can lose the siphon over the edge of the tank when the flow stops.[/QUOTE]
I'll check to see if that helps as well.
My aqua lifter is prone to clogging unless u use thenprefilter which I broke. Keep an eye on the outflow of the aqua lifter and make sure it's working properly or itnwill keep losing siphon
I don't have a prefilter, nor did I know they had them. So far they still suck water great, but for some reason it doesn't seem to have the strength to reprime the 55g, my 125 has been up and running longer and never has a problem with the prime when I shut the power down. I will take a look at it either way, what is the best way to clean the aqua lifter?