Boiler troubles

[88v8]

My system is about 10 years old and has not been altered, nor does it have any tanks in the attic, being fully pressurised. What has happened over the 10 year period however is the taking off of radiators for decorating and subsequent replacement. Clearly when this happens water is lost and has to be topped up.

And so the water treatment is diluted ....

Before they come round I'd buy a Fernox test kit, available through that link I posted or perhaps from a plumber's merchant, and check the water yourself by draining off a smidgeon.
If you're under-dosed, that wil tell you immediately, then you'll know you've found the probable cause.
Otherwise, draining & flushing might remove the adverse symptom - sludge - without you being any wiser as to the root cause.

With wall-mounted cast-iron rads, they can be pivoted down from the wall without disconnection from the system, thus no water loss. I guess a few years to late for you to know that...

Ivor

 

[Nigel Watts]

Ivor

Householders should be left instruction manuals for their systems. I had no idea that the water had additives to prevent limescale and corrosion, although it makes perfects sense, nor that one should test annually to see if the concentration is high enough, and if not to top it up. I have just looked at the British Gas service checklist and notice that there is no box to say that they have checked this.

I assume that this is what I need to have done:

http://www.youtube.com/watch?v=NDZmBXXBxR8

 

[88v8]

Ivor

Householders should be left instruction manuals for their systems. I had no idea that the water had additives to prevent limescale and corrosion, although it makes perfects sense, nor that one should test annually to see if the concentration is high enough, and if not to top it up. I have just looked at the British Gas service checklist and notice that there is no box to say that they have checked this.

I assume that this is what I need to have done:

http://www.youtube.com/watch?v=NDZmBXXBxR8

Yes, but would most householders read them? Hmmmm. How many read the manual for their car or the instructions for the camera....

That Fernox process includes a full acid descale. You might only need sludge removal. However, if makeup water has been added without treatment, as you describe, and you live in a hard water area, then each addition of water has brought with it a concomitant portion of scale which deposits preferentially on the hottest areas, particularly the boiler heat exchanger whose efficiency is thus impaired. If the heat exchanger cannot shed the burner heat into the water, then it will overheat at high boiler settings. Modern exchangers are alloy and are designed for a high rate of heat transfer, if this cannot be achieved due to scale - even a small flash of scale is detrimental - then they will distort and eventually fail. In the meantime, knocking noises from the boiler at high temperatures may give an early warning that not all is well.
In this case, yes, you will need a descale as well as a flush.

In an older system with modern steel radiators this is not entirely without risk; steel rads are thin and untreated water will corrode them into holes, it may be that the only thing preventing leaks is the coating of scale.

It's a pain. Bring back the open fire, eh, what?

Ivor