HJK2005's post in Aqua hot was marked as the answer
Hello Don, that is a 1/2" check valve. You have one for each zone of the Aqua Hot. They turn blue/green like that when there is a leak that allows the boiler liquid to get on the outside of the valve. You can Google "1/2" brass check valve" and there are various sources for them. Here is one link for Lowe's: https://www.lowes.com/pd/AMERICAN-VALVE-Check-Valve-Brass-1-2-in-Fnpt-Swing-Check-Valve/1000248917?cm_mmc=shp-_-c-_-prd-_-plb-_-ggl-_-LIA_PLB_142_Pipe-Fittings-_-1000248917-_-local-_-0-_-0&ds_rl=1286981&gclid=CjwKCAiA5Y6eBhAbEiwA_2ZWIYMQpNnTMIHRPQPGGxqzC_VzUZ0sDJJ7lktNoNxPilhPmXMjZZn41RoCGzIQAvD_BwE&gclsrc=aw.ds Hope this helps. Feel free to reach me directly if you have any questions. I just did a complete once over on our Aqua Hot. Happy RVing. - Jonathan
