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Unread 04/28/2011, 01:19 PM   #25
kcress
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Join Date: Dec 2007
Location: Central California Coast.
Posts: 5,383
Yes I see a few bubbles..

Track them down. Is it the water rushing by the vent hole? Put your finger on the vent hole during a dump. Water rushing by a hole can suck air in.

If that's not it, it's the trapped air in the column below the siphon. It has no where to go but out the bottom. You need a way for it to escape once the large slug of water shows up. Try putting a standpipe from right at the surface to above the water level of the siphon. It needs to be big enough for the air to escape out of faster than the water slug shows up. I'd guess about half the siphon pipe diameter or larger.

To deal with this people often mount their discharge half in the water half out of the water. That's where the air escapes during a surge - just above the water line. Of course that can cause some splatter too.

This gives me an idea. I could build one like mine but put a concentric central pipe back up the center and clear out the top thru the cap. Then the outlet could be fully submerged with an internal air escape. That would require straight piping to the water, but that's what I always did anyway.


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