Reducing noise in Grundfos Mains Booster Pump

[MKP]

Hi All

I have a Grundfos Mains Booster Pump in the loft - it provides pressure for all the hot water, and most of the cold water flow in the house.

The pump is mounted on a 3-4cm thick piece of sound insulation board, on a piece of wood which is attached to a metal bracket, which is itself then attached to the chimney breast wall in the loft. The pump is in a plywood (I think) box, which is then surrounded by more insulation material, and then by another box.

The pump is on a timer, so that it doesn't run overnight.

The problem is that despite all the insulation, the pump is still very audible throughout the house, particularly in the bedrooms when it comes on first thing in the morning to refill the tank (I presume) of any water that has been used since it was turned off the night before.

I have now asked 3 plumbers for help in reducing the noise - either by adding rubber between the pump/wood and bracket/wall, or by moving the pump to an external wall, and none of them seem to want to touch it!

Can anyone suggest any other ways of reducing the noise - and can anyone explain why this seems to be such a scary job? Is it that hard to disconnect the pump and reconnect it (which would need doing to put rubber in or to move the pump)? All the plumbers have made comments that they worry that when they reconnect the pump things might not work right - am I missing something obvious about how these things work?

The only other option I can think of is to move the timer switch to somewhere out of the loft, set it to not come on so early, then manually turn it on if we need it earlier than it is normally set! It doesn't really solve the problem as much as avoid it...

If anyone can recommend a plumber in the SW London area who would know about these things I would be REALLY grateful!

 

[JohnKay]

Hi MKP

The first thing I'd ask is, is the pump really necessary ? If so, then you mention that it is enclosed in a box. This should not be so. the pump should not be covered in insulation, but should be in free air. Who knows what your plumbers are seeing, and not telling you !
The best way forward I think is to use some proper pump fixing brackets. Sorry to say, I can't provide a direct link, I've always obtained locally. If you go to Direct Heating Supplies website, and search for pump brackets, there's an image of the type I mean. I hope that helps.

 

[Ian]

Hi MKP, welcome to the forums .

Is the pump a Grundfos MQ3 (quite large) and is it connected using copper pipe? John is quite right in that the pump will need ventilation, so having it completely boxed in may not be a good idea.

If it is one of the larger booster pumps, you could try using flexible connections to minimise vibrations, as well as using a better damping mount. If it's the MQ3 or one of the other larger pumps, then you may need to check the internal pressure vessel and make sure that it has the correct charge (these are user serviceable and need occasional maintenance). These are very small (0.16L) vessels that are used to protect the pump and stop the water hammer type sound that you sometimes get (plus provide a little bit of pressure for very small leaks in the system).

If you know the model , we may be able to give more advice .

 

[MKP]

Goodness only knows. I know that when the pump isn't running the water pressure is pathetic - dribble would be an overstatement. However whether that would be the same if the pump wasn't there at all I don't know - I don't know if a non running pump blocks the flow!

I think it is an MQ3, but I'm not sure I could tell you whether it is copper pipe! It's not completely boxed in (there is some air flow at the side) but the manual says that as it is water cooled that's OK....

Next time I go up into the loft I shall take all the boxes apart (again) and tell you the model and the pipe type...I did have a plumber look at it so I *presume* he would have checked the internal pressure vessel (or is that over optimistic??).

Can you recommend a better damping mount?

Thanks for your help!