On the Polaris 360 there is a pressure relief valve right where the water feed line connects to the swimming pool filter water supply. The pressure relief valve is there to let excessive pressure out before it gets to the Polaris 360 itself. My pressure regulator opens up at fifteen pounds or more to keep from over pressuring the Polaris 360.
I have found that the excessive pressure going to the Polaris 360 is caused when the pressure going into the pool filter increases. Since the Polaris 360 is powered by the same pump that runs the pool filter so some of the water that is supposed to go into the filter is diverted into the Polaris 360 instead. as the filter gets clogged and needs to be washed, in the case of a cartridge filter, or backwashed, in the case of a sand filter, the water cannot get through the filter so the pressure increases and the excess pressure is shunted to the Polaris 360. Once the pressure increases above fifteen pounds the pressure relief valve opens up into the swimming pool.
As long as the pressure relief valve spring and assembly are intact it should be easy to prevent the excess pressure just by backwashing or cleaning the filter.
