I have an MR2-R with a large waste container. The skimmer is being fed from the return pump and flows the water back to the sump. The skimmer sits above the sump water level and the output is plumed with a 90 degree angle pipe and directed to flow under the sump water level. Here is a picture of the setup before it was turned on, note that the pipe going into the sump was extended:
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I adjust the gate valve so the water level is just under the quick connect so I can see the foam.
Now, it works ok for a a day or two as in it starts filling the collection cup with green nasty stuff, but then after a day or two, for no apparent reason I will find it had overflowed and filled up the waste collector. This happens quite consistently... what am I doing wrong?

I adjust the gate valve so the water level is just under the quick connect so I can see the foam.
Now, it works ok for a a day or two as in it starts filling the collection cup with green nasty stuff, but then after a day or two, for no apparent reason I will find it had overflowed and filled up the waste collector. This happens quite consistently... what am I doing wrong?