I'm in the process of replumbing the return line after my filter to add lines to the solar panels I'm attempting to add to my setup.
Currently, there is a single union ball valve on my return line immediately after my filter. The non-union side of the ball valve is solvent, and there's not enough pvc between it and the mipt fitting that screws into filter to salvage it. I'm not a plumbing expert, but I can't think of a good reason for it to be there. I can't imagine it would be good to 'throttle' the amount of water the pump was sending back to the pool. The union part of it is helpful for winterizing and removing the filter from the system entirely when I clean it. Should I replace this ball valve with a plain old union, or should I replace it with another valve?