Drain C/H system to change secondary heat exchanger on combi?

Not if you can close off the system isolation valves. Then you only need to depressurise and drain the boiler

I can close off the system isolation valves. How do I depressurise the boiler?

Thanks again,

AL D

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Most combis have isolators on the flow and return connections. Follow the procedure in the manual.

If you look in the manual it should show the location of the drain point. Don't use the safety valve as they almost always get a bit of crud under the seat and will not seal properly again.

Yes! The manual showed a drain plug under the diverter valve, but when I looked, all I could see was solid black plastic! So I had to use the pressure releif valve - and yes, you were right: it dripped afterwards. I took it to bits and cleaned it but it still dripped! So I smeared a bit of silicone grease over the mating surfaces. All is watertight now.

Cheers,

Al D = = = = = = = = = = = = = = to email me, first remove the three-letter animal from my email address.