PentAir's brochure shows 2 types of the controls:
521592: SolarTouch Solar Control System with 3-Way Solar drain-down, valve actuator and 2 temp sensors (20' water, 40" solar) and
521632: SolarTouch Solar Control System with 3-Way Valve, valve actuator and 2 temp sensors (20' water, 40" solar)
The only difference is the valve and the first type is mentioned that it's a drain-down. Also on the spec page it mentions:
This is somewhat confusing to me. Can someone explain the "drain-down" feature of the valve? I feel that it would drain itself any way (towards the pool if there is a check valve between the T and the filter). I assume there is no check valve built in into the 3-way valve itself, is there?Solar valve automatically drains the solar collectors when pump shuts off
Also, on somewhat unrelated note, I assume neither PentAir no Jandy check valves can be installed on vertical pipe, is that correct?