Boiler - Surging And Kettling

Vern1961 · 18 Apr 2013 at 10:16

About a week ago we had our heating engineer to change out the pump as it was grinding and squealing on start-up and sometimes when running. While changing it, we discovered the cold feed pipe from the header tank (it's an open system) was blocked by sludge so he had to cut in a bypass to refill the system. System filled alright and new pump working, but when it's running you can hear the boiler banging and occasionally kettling, accompanied by surging and gurgling from the pump and three way valve. I've tried bleeding the pump, the rads and the air valve on top of the pipework to no avail.

We have used this engineer for some years but I'm beginning to doubt whether he can fully sort out the problems. I'm also beginning to wonder whether the system itself is just basically shot. I could try getting a power flush done but we had one just over five years ago and if the whole thing is so badly sludged is it really worth spending the £250 - £300 which could go towards getting it all replaced?

Vern1961 · 18 Apr 2013 at 12:46

It's a British Gas RD1, not sure of the vintage though it was already installed when we moved in just over seven years ago.

Vern1961 · 24 May 2013 at 03:27

Still trying to bottom this out, no end of bleeding both the pump and the air valve seems to be clearing the problem - which seems to be when the hot water is running rather than the radiators.

One thing I have wondered, is when the engineer recut the feed pipe, he may have joined it into the vent pipe - could this be responsible for throwing the system off balance? I've also noticed in the pipework above the boiler in the kitchen is a draincock, might opening this release some of the trapped air?

I may have a go at draining the system down fully myself and refilling, though not really the time of year as ideally I want to run some cleaner round the circuit for three to four weeks before draining down again and refilling with fresh inhibitor. However not much point if it's only going to scrub the HW circuit and not the rads.

Really I should call the engineer back to sort out his mess but missus insists we never let him set foot in the house. May have to resort to getting British Gas in if the above steps don't help but I can already hear the screams of protest from my current account...

Vern1961 · 5 Jun 2013 at 08:43

Quick update... Gave in and got British Gas out last week (signed up to a 12 month contract). Engineer changed the 3 way valve then when he came to refill the system discovered the feed still blocked via the vent pipe.

Appears all that happened when the previous engineer ran the cold feed bypass was to fill up the vent pipe. Upshot is we have been running a half filled system for the last two months - no wonder it was noisy and a miracle it didn't break down altogether.

British Gas guy had to cut the pipe at the T junction and clean it enough to get the water flowing. System now filling okay and running quietly apart from the odd bump from the boiler, probably limescale from running half full.

British Gas coming back at the end of the month to do a power flush and fit a magna-filter which will hopefully improve things. One question, is it worth adding some cleaner to the system now before the power flush or is that not going to achieve much, bearing in mind the rads won't be on?