if the suction forms an venturi on the water surface it will suck air into the pump that will make a big noise, what we have done in big pump stations where this problem occurs we throw tennis balls onto the water, and that will prevent the pump to create a venturi .Normally a venturi starts when the water level is to close to the suction pipe,so what you can do is to rise your water level.Ben please explain that.
You would think I knew this by now... If I remove the pipe to check, will water come gushing out the pump? (AP600 external skimmer)Gaboon - sometimes the air-pipe connected to the venturi's become clogged. There could indeed be some water droplets (from condensation, splashing, etc) that have come into the venturi air-pipe.
A few things you can try:
- drop a very small amount of vinegar into the airpipe
- drop some RO water into the airpipe
- enclose the airpipe for a few seconds, that a vacuum is created within the airpipe -> on the release of the airpipe, the vacuum will force air through the venturi, forcing any/all blockages to be forced "clean" into the pump and into the skimmer.....