Originally Posted by
johnnyd
http:///forum/post/2835572
the cpr looked better IMO and better built, i read you have to keep the AL clean and the air hole it plugs into then you should be fine. on the u-tube if air builds up theres no way to get it out with out restarting the siphon right?
The problem with the CPR overflows and the other knockoffs is they rely on the aqua lifter pump to maintain the syphon. Because of their design the water traveling through the oveflow does not have enough velocity to carry any trapped air out of the U-tube so they want you to use the aqualifter to pump out the trapped air bubbles. These overflows are also prone to leaking they don't drip water when they are running but during a power outage it allows air to enter the overflow causing the syphon to break. With the one that I had it would lose its syphon in about 15 minutes so when the power came back on the aqualifter would have to restart the siphon from scratch and could not get it done before my return pump would overflow the DT it wouldn't overflow much just a few ounces but that was too much for me. Then on top of it all the aqualifter pump is not the most reliable piece of equipment it is generally reccomended that if you buy one buy two because it is eventually going to fail it may go a month or a couple of years (I don't think I have heard of anyone having one last 2 years) but it will fail. Then like you had heard you can get salt creep on the airline fitting and inside the airline which would stop the aqualifter from pulling the air out. Just too many things that can go wrong.
With a correctly setup U-tube overflow you will never get air trapped in the tube. If you are getting air trapped in the U-tube it means that your return pump is too small or is restricted too much either way you are not returning enough water to the DT to maintain the siphon and carry any trapped bubbles out of the U-tube. As long as you maintain your pump and clean the U-tube periodically they will run without issue for years.
I believe the overflow that I have is a Lifereef and it has been fine, the Eshopps is built a little better and is the cheapest overflow that I have seen.