Red Sea Reefer 350 G2+ cannot maintain stable return flow

[Mr31415]

I have found similar issues by fellow reefers, but with no solutions. My Red Sea Reefer 350 G2+ is a year old. I believe it has the newer style return control valve. For the past 11 months it has been pretty good. I have dialled it in and it maintained a water level between the short overflow pipe and the emergency pipe in the overflow chamber - perfect flow and silent. I only sometimes had to adjust it slightly.

The past month or so has been terrible. It would be fine for a week, then within 2 minutes with no changes, it will either drop so low in the overflow chamber that it makes terribly gurgling noises, or it goes about 1/2” above the emergency overflow pipe and causes my ATO pump to cut off due to running for too long. I would then adjust the control valve about 60 degrees, wait 2 hours, repeat. It takes about 360 degrees of turning over the course of a day to get it to start to swing the other way. Many times it then goes straight to the opposite end - too low or too high. After 2 - 3 times of this hassle, I would get it dialled in to be half way between the two extremes. It would work fine for anywhere from 1 day to 5 days, then toggle again all on its own.

I opened the control valve and there was only a little bit of algae which I cleaned. The mechanism felt sturdy and undamaged. I completely cleaned the Red Sea reef run dc 5500 pump (set to 40%), it was not very dirty. Nothing is blocking the return pipes. The fact that it worked well for a long time tells me it is not flow rate. I adjusted it down from 43% to 40% and it made no difference.

Here is a picture of the sump level to prove how quickly it swings

Any ideas?

 

[OctaviusBrine]

I had a 250 and went through that trouble as well. I replaced that Red Sea valve with a gate valve. Ran it that way for over a year till I sold that set up.