Our hot water re-circulator, just installed, is adding cold water into the pipes after about 20 minutes of re-circulating (with hot water not running during these 20 minutes, so thus, not running out of hot water). Thus, showers are lukewarm instead of hot, thus defeating the purpose of the re-circulator. Any suggestions of why and how to fix?

Depending on how things are piped, defective check valves.

It can be number of things. First, make sure it was installed the way it should be and that there is no cross-connection in the system. Also, as Harold mentioned above, make sure all check valves are in proper operational condition.

I would call the installer back and asked him to go over his installation to assure all is installed as it should.

Milo

Agree with all ,call you installer back. Did he also sell you the valve?