oscillation in pool loop with above-roof solar panels

[mas985]

No, right now everything is below the pool level, and I don't think it is feasible to change that---I would have to run many pipes a long way.

Actually shouldn't have to run anymore than you are now (2). The solar valve would just bridge the two pipes running up the house in a H configuration. The check valve would just be before the H on the supply side. Similar to below. The only difference is the pump and filter is lower than what is shown in the picture. But you only need a supply pipe and a return pipe to and from the house with the diverter valve. Also, they don't show the check valve but you should have that right before the diverter.

[semenzato]

Yes, the picture corresponds to what I have now, except that pump, filter, and diverter are about 8 ft lower. Also, as you said, I have a check valve between filter and diverter.

I also have an additional check valve on the heated water return, near (4) in the picture, probably to prevent backflow into the panels when the diverter is in the non-solar position. But since i am leaving the diverter in the solar position, that shouldn't matter.

Thanks!

[mas985]

So what I was suggesting was to move the solar valve and both check valves so all are above water level. That should not require any additional piping. It is basically moving the H ~9' higher.

[semenzato]

The house is on a hill, with the main floor level with the pool. The equipment is in a room in a floor below. There is no easy way of moving the position of those valves.

This didn't use to be a problem. I am not sure when or how it started. I made small changes here and there. For instance, I added a separate loop, with two diverter valves, to reuse the same pump, filter, heater, and chlorinator, with a hot tub, so some of the pipes changes. Evidently some of those changes were enough to create the oscillation.

[mas985]

OK then pictures might be useful.