I typically use an expandable rubber plug in my skimmer when I close my pool for winter. I pour good amount of ethylene glycol based antifreeze into it and stuff some pool noodles. Last year somehow I didnít get much additional water into it over the winter and antifreeze stayed undiluted. The top part of the plug had rubber all shriveled and misshaped. Which seems to be an effect from the ethylene glycol. Which is not a big deal, since a rubber plug is under $10 and can buy new ones every season.
This upcoming winter will be my first one with solar system. I planned on adding some glycol to the pipes around check valves, 3 way valve and possibly bottom header of the panels. But now Iím concerned with rubber gaskets on the expensive valves and connecting rubber hoses between the panel that form the bottom header.
I tried to find if glycol indeed reacts with rubber and it seemed to be a case. However there are tons of different rubber types.. So Iím wondering if anyone had an experience/knowledge with this and can share something thoughts. I found this page about rubber resistance, but not sure how helpful it really is: