Hot Water Issue

chappers

southcoastrgi wrote: »

As above, you have paid for a powerflush, the water should be clear get him back to do the job properly

Exactly, sounds like a half ar5ed job, which has probably loosened the sludge but not removed it all. the sludge won't all be magnetite, so not necessarily magnetic.
I power flushed our system years ago and on the advice of a plumber I trust, flushed the rads individually whilst disconnected from the system, as he suggested that was the proper way to do it rather than the accepted practice of just isolating and re-introducing each rad into the system for flushing.

onomatopoeia99

My boiler had similar symptoms not long after I moved in. CH would work but when I tried to use the hot water it would cut out with an error code.

After much faffing around, a new diverter and secondary heat exchanger installed by a plumber both not fixing it and the problem evidently being the primary heat exchanger, I fixed it myself by running X800 around the system for a couple of weeks. I was only doing it as an experiment while quotes for a new boiler came in.

The primary heat exchanger was clogged, which meant water flowed through it very slowly and when the burner fired for the hot water the water would boil inside it and it would sound like a kettle - the error code on the boiler apparently meant the flow and return temperatures were too different and it couldn't modulate the flame properly. Putting the X800 in the system and restricting the CH to a single radiator (the shortest run from the boiler) allowed it to unclog everything and it started working again. Took a couple of weeks though, in a cold November, with no CH and no hot water. I then drained it (the water was black), refilled with another dose and ran that through the whole system again for a more couple weeks, drained it again and this time refilled using an inhibitor.

So far in five years I've not had the same problem again, but I do put inhibitor in each year.

Ectophile

If the water's thick and sludgy, then it's going to keep clogging the boiler. It sounds like you need the system cleaned and re-filled, making extra sure that new corrosion inhibitor is put in.

If it doesn't currently have corrosion inhibitor, then it is slowly rusting away your central heating system from the inside out. You could soon be looking at a new boiler and a new set of radiators (been there, done that ).