A pulsing whine from our heating system was driving me mad. I traced it to the circulation pump on the house's radiator circuit. Cleaning a thin layer of black deposits from the pump stopped the noise and saved me from replacing a pump that otherwise appeared to work.
This is a description of my own troubleshooting, not a general instruction to dismantle a heating system. Electricity, pressure and hot water can all make pump service hazardous.
First identify which pump you are looking at
Our home is connected to district heating, but the pump I worked on belongs to the house's secondary radiator circuit, not the primary district-heating side.
If you cannot confidently identify the circuit, isolate it, switch off the electrical supply and remove pressure safely, call a heating professional.
What I checked first
I started with the obvious: bleeding the heating system and listening for any change. The whine remained. A replacement pump was expensive enough that I wanted to know whether the problem was actually mechanical wear or simply dirt.
Our installation had isolation valves around the radiator circuit. I switched off power to the pump, let the system reach a safe temperature, closed the relevant valves and made the isolated section pressure-free before removing anything.
What I found inside
There was no dramatic blockage. I found only a thin black film. I wiped it away, inspected the pump and reassembled it.
After reinstalling it, I reopened the circuit, restored the correct system pressure and bled the system. The result was immediate: silence.
What else can cause circulation-pump noise?
Cleaning will obviously not fix every noisy pump. Other causes can include:
- air in the system;
- incorrect pump settings;
- a blocked filter or strainer;
- cavitation or unsuitable pressure conditions;
- bearing or rotor wear;
- a pump that is simply at the end of its life.
The useful lesson for me was broader than this one pump: diagnose before replacing parts. Sometimes the difference between a repair bill and an hour of work is simply finding out what has actually failed.
