Cleaning out a DHW heat exchanger?

[A.Lee]

My boiler is playing up again, so it looks like the heat exchanger will have to come out tomorrow for its periodic clean up. Last time I did it, there was a lot of 'blackness' on the internal walls of the exchanger, but no readily seen build up of sludge/muck in it. I gave it a blast through with a hose pipe, and it worked fine again that time, but it has only been 4 months since I last did it.

So, the query - is there anything I can pur into the exchanger to give it a good clean internally? IIRC, it is an aluminium casting. Thanks Alan.

[Martin Pentreath]

Mine was regularly clogging up until I flushed out the whole system and put fresh inhibitor in, when did you last do that?

[A.Lee]

Sorry, I should have made it more clear that it is the domestic hot water that is playing up, not the radiators. AFAIAA, they are totally separate - the problem with the DHW exchanger is that it is so small, so easy to get blocked/gunged. Ta Alan.

[Ed Sirett]

Since one half of the DHW heat exchanger contains primary circuit water one half of the problems with it can stem from the primary circuit.

The other half are chalk in the DHW side.