A little help please. I am trying to install a 4x20 Solar Heater on the garage roof next to the pool. Height is only 7 feet and garage roof is only 1/12 pitch so I want to mount the panels flat to the roof. As well I am hard piping it in and I was planning to mount the valve about 3 feet up the wall. This will leave me some room to install the SWG cell when it arrives. I need the valve so I won't use the panels at night. A 2-way valve came with the kit. However, the instructions seen to suggest installing the 2 way between the lines "going to" and "coming from" the heater which makes sense to me. My concern is: It seems to me that with the 2-way valve installed between the lines either up the wall or on the ground it will allow for the panels to bleed off when I open the valve thus having to reprime the panels daily. Question. Is my thinking of bleed off correct, is there a better location to install, and should I think about a couple of check valves to help? Thanks in advance for the help. Dave S.

Hot Sun Industries has some great diagrams of the best way to plumb solar panels.

You want the panels to drain down any time the pump is off.

Using the link Jason provided, I would pay some attention the the discussion about a diverter valve. I say this since you propose only a single panel (low GPM flow needed) and also want a SWG (which may need more flow). A diverter will split off some water to the solar panel, then the flows can rejoin before the SWG.