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Originally Posted by Psycho graphic  |  | | | | | | | | | I've seen that site, it does'nt explain how or why they work though.
As I see it the submerged end obviously does'nt allow for air to enter, therefore it won't allow it into the tubing, but won't the vent allow it to draw air, thus creating noise?
I almost get the idea, I'm just missing one part I think and it's driving me crazy as I usualy can understand things like this.
If you have a perfect balance of return and drain that does'nt allow any air to enter the tubing, why would it make any difference as to how big the vent is? | |  | |  | |
In theory, but you are never going to have a perfect balance of return and drain, where the exact amount of water you are pumping into the overflow matches exactly the size of the reutrn line. And if you do, then don't worry about durso stand pipes.
When the water is rushing down the pipe, it creates suction. That suction will pull water out of the return, until the mouth of the pipe is exposed and then it will suck air. It will suck air until the suction brakes, and then water will fill the pipe again. As the pipe fills with water the pressure builds, wich will eventually create more suction. By regulating the hole, you are trying to feed enough air into the system to avoid the suction. If the hole is to small, you create suction, if the hole is to big, you end up pulling to much air into the system wich is also noisy.