Baxi Bermuda 552 & Scale

[yellowrecord]

I've had a long running problem with scale in an old Baxi Bermuda 552 back boiler. I live in London and suffer from hard water.

I've used fernox DS3 on and off in the past and this has always helped.

This winter the system was clearly labouring and giving only lukewarm radiators.

My local supplier only had Fernox DS40, not DS3. 'It's stronger' he says. 'Just use less' he says.

It improved for about a week and was then worse than ever.

I'm now on my 3rd lot of DS40. The boiler fires and bangs every half an hour or so and I know the chemicals are working because a fair amount of gas is evolved, but there is no heat at all, not even as far up as the pump.

I think the earlier DS40 has been so efficient that it has dislodged a considerable amount of old scale and blocked the boiler.

What I want to know is; will the DS40 eventually clear it, or is there some other effective treatment I should use ? At the moment moving house seems like the best option.