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Has anyone got any idea or experience of this, please?
Yesterday, a Grundfos UPS2 25-80 pump started making a surging noise, about once a second. It's still running, but very noisy.

It is mounted vertically, and there is something of a loop above it. But it's worked okay for many years.

Could it be air causing this odd sound? Or something else? Or is the whole pump dead?

I have a video that I've not been able to post using the YouTube buttons.

Thank you for any help!

Sounds like air, are you sure the system is full? Is it a sealed or open system? Any air vents above the pump? A photo of the pump and pipework above will help.

Thanks for your reply.
Here are some photos:

And I have an audio recording and also a video, though I'm struggling to make the YouTube link work. I'm told it's external to this domain and I can't post!

As an anti-spam measure new members cannot post external links until they have made 10 posts.

Ah! Okay, I understand. Well then, I'm up to four, so making good progress!

I'm really trying to narrow down on whether I should get a new pump in because it's died, or cut into the top of the loop of 28mm copper, put in a reducing tee with an air vent cap to see if there's air trapped up there first. This would, at least, be a relatively cheap approach before getting a whole new pump!

have you tried bleeding the pump ?

https://www.youtube.com/watch?v=8DDZ1Y1 ... =dereton33

Good photos.
Almost certainly air in that top pipe, needs a way of venting at the high point , the fact that it would appear to be on the negative side of the pump also means the pump is sucking rather than pushing so less chance of clearing.
The pump should be pushing toward the valves which is correct.
I am surprised it has worked till now. I cannot see the gauge clearly has it got at least 1 bar of pressure?
Ideal solution would be to fit an air vent on a short vertical pipe at the high point, what is above, loft, upper floor? Can you access to fit a vent like that?
After you may find the pump is noisy because the bearings may have run dry, but see how you go.

wine~o wrote: ↑Wed Sep 11, 2024 11:38 am have you tried bleeding the pump ?

https://www.youtube.com/watch?v=8DDZ1Y1 ... =dereton33

Worth trying, loosen the centre screw on the pump and see if any air comes out. Long term it needs a bit of alteration as I suggested

Ah haa! Thanks for the suggestions and help. I was coming back to say... sorted! Kicking myself for not noticing sooner that all the pressure had gone. Zero bar. As soon as I started to recharge the system, the sound went. So thanks again, and hopefully this thread might help someone fix theirs sooner in the future!

Seems to be running like normal now.
I do think there's merit in putting an air vent in, but this has been de-prioritised right now!
But something that I would prioritise, if it's possible, would be giving the pump some love: can it be serviced/can the bearing be re-greased?

Thanks again for all the input.

Good glad it is ok, as long as the pump is not making any grinding or scraping noise it is OK!
Once they go the only thing is to replace them, they are not greased, they rely on the water for lubrication.

Okay, so important not to let it run dry!

I'll pencil in an air vent for next time we're doing stuff.

Case closed, thank you for all the help.