Recirculating pump issue.

[Califkd]

My system has had a recirculating hot water system for 20 years. Over the last few years, we noticed the pipes were thumping on the far side of the run.

Now the thumping is gone, but half the house does not have instant hot. Even in the bathroom on the far side has two sinks with differing temperatures.

Do I have some blockage, or a pump going bad.

 

[Mr_David]

Post a picture of the pump, include the heater if you can. I know what a pump looks like so I want to see type and how it's set up.
Do you have designated return line?

sometimes that line can be air locked and the pump will not move the water.
maybe a bad check valve clattering and stuck in closed position.