Wilo Pump noisier than Grunfoss?


29 Mar 2015
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United Kingdom
I have an outdoor Grant Combi 90 Mk2 oil fired boiler. The pump had to be replaced recently. Grant now supply Wilo, however after installation the system is now noisier when running and is omitting a 1khz tone, which is louder inside the house than at the boiler itself.

This pump has a three position speed switch. If I turn it down to position 1 the noise is reduced but in my opinion its still louder than the grunfoss. I have bled everything ( boiler, pump, rads etc) . Can it run effectively on Position 1? I feel the Grunfoss was still quieter. Any ideas?
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Grundfos is a superior product and lasts longer.

Wilo is cheaper. If you want a Grundfos, go out and get one.
A 1 kHz could only really be created by the impeller if its a traditional induction motor model.

I would be removing the pump head and inspecting the impeller.

Although I am aware that some householders are very over sensitive to minor noises that would never bother anyone else!

Has it been noisy from fitting?
Has the pump been bled properly?
Have the valves been opened fully?
Is there sufficient pressure in the boiler?
If so, and you still have the noise, then suspect faulty pump. Call your engineer back.
Running on speed 1 may not give you sufficient hot water
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Thank you for your posts.
Oilhead - The noise was there from the off. It was only installed a week ago. Re bleeding, the screw on the front was opened. Is there any other way to bleed it?

Which valves are you referring to?

Agile - Im not clear what the Impeller is?
I am referring to the isolating valves at each end of the pump. They open like taps with a small square ended spindle. Make sure they are fully open, anticlockwise.
To inspect the impeller, you need to dismantle the pump. Don't go there. If this is the problem, then the pump should be replaced.
I will check this in the morning - Are those both screws that need turning on the valves? or are we talking spanner?

The plumber who installed popped in to listen. As the noise is louder in the house than at the boiler itself he is of the opinion that matter is possibly trapped in pipes somewhere and a flush, which i think I need anyway, should be done. As I mentioned in my first post if I turn down the pump the noise alters...
If there is a tight bush in the pump, when you slow it down, it will make less noise. An old dodge is to place a long screwdriver on the pump body, and place your ear on the handle end. If there is any roughness you will hear it transmitted through the shaft of the screwdriver.

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