Humming water heater

Last week it started. Every time the hot water was run there was a loud humming sound. After doing a little research on line I figured out it was probably the check valve. According to what I read, there could be one or two check valves. I decided to remove the cold water side first and with a 50/50 chance, it didn't have one.  Next I removed the top one. I found a 1/2 inch spring loaded check valve. It was visibly bad. The o-ring around the piston was partially on top of the piston instead of being underneath it. 

Now to go get a new. After 3 hours of running around between Carbondale and Glenwood Springs no one had one.  I ended up ordering one on Amazon at the tune of $24.00. Replaced and no more humming!

Old check valve with o-ring messed up. The hummer culprit!

Plastic piston - leave it to the RV company to get the cheapest

Top of water heater with the new check valve

Disconnected

New check valve with no plastic parts

New

Old