Circulation pump/pipe rattle

[Robert Jones]

Home inspection today. The house was 13 years old and there is a Grundfos circulation pump installed at the water heater. After running some of the fixtures, the pipe which runs away from the circulation pump was rattling(sp?). Would this be cause bu an unsecure pipe? What are some of the other possible issues?

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[kurt]

They usually rattle before they fail.

[hausdok]

Cavitation? Did the flow of hot water you were drawing off get ahead of that little pumps ability to keep the line full of water?

ONE TEAM - ONE FIGHT!!!

Mike

[kurt]

They don't usually rattle when they cavitate, they just get really hot on the end bearing. Really hot.

[Robert Jones]

Thanks for the replies. I couldn't pin place the exact location of the rattle, but, it sure sounded/felt like the riser pipe. There was no heat or hot spot to speak of. Kurt, your opinion is that the pump itself is close to failure?

[kurt]

I can't tell from here. If it was an old circulator, it certainly could be failing.

The rattle at the riser pipe instead of the circulator could cavitation. Next time, put your hand on the rear of the circulator; if it's super hot, it's probably air locked/cavitating.

[Robert Jones]

Thanks Kurt