bonus solar isolation valves

[rcairflyer]

I have solar mats on the ground which I plan to move to the house roof. The solar lines between the pump and the house will run underground. There will be no way to gravity drain the lines at the pump and I'm concerned about winterization ( NJ ). Can you blow out pipes when there is a air relief in the line? I don't imagine you can, so I'm consider putting a union on each line where they go vertical at the house. Or valve/union combo (hayward sp 723). Valves at the house and at the pump would amount to an extra set of isolation valves, but it would make winterization a bit easier. Open the lines, blow them out at the pump, and watch the geyser. Does this make sense? Or is there a better approach?

On the solar supply line I need a check valve to prevent backflow and backwashing the filter. Do I need one on the solar return? I have an isolation valve there already.

Lastly, I see a lot of installations using 10' or 12' mats run vertically. I'd like to use my 20' mats (3 * 4x20) and run them nearly horizontally (I'll pitch them 5 inches to drain). My ranch roof has room for them. Any reason not to use them?

 

[jblizzle]

Welcome to TFP!!!

I am not sure what to suggest for the winterization, but will address the other questions.

Is the system going to be automated with an actuated 3-way valve? If so, then you would typically have a check valve right after the filter and then another one on the solar return line to prevent flow to the panels backward with the solar valve is off. If not, and you are just going to use isolation valves to turn the solar on and off, then you would not need a check valve on the solar return.

I think some people have used the 20' horizontal mats on roofs, but how much is the roof sloped were they will be sitting? If there is too much slope, the mats tend to sag in the middle.

Realize that you will also need a Vacuum Release Valve in the system when you raise the mats off the ground to facilitate them being able to drain when the pump is off and not being damaged.

 

[rcairflyer]

Thank you for the reply. The pitch is 4.4/12. The mats will need tie downs more for wind than for sliding.
I'm probably overthinking the plumbing. I can just install an extra fitting here or there and get the project done. The concern then is things like ball valves going bad. So I'll use a threaded valve and include a threaded union.