39 heater shut off valve

[adileo]

I installed a valve in my head to shut heater in summer months.

In doing a little reading here on Barn, I understand the antifreeze flows from bottom up to top of block and exists. If this the case then while the valve prevents water from coming out of heater. The lower hose continues to have pressure pushing water in.

Do you need two valves?
Is there a pressure continuing to try and push antifreeze in?

Thanks Andy

PS: I have never seen a shutoff valve in any other location other than the head