Hello and help with a microbore system!

[Stigster]

Stigster you are correct! The problem with ripping it out is that it is in the walls.

I fully understand your dilemma. If you are left with no real choice but to reuse the microbore system, as it is several decades old at this point I would at the very least want the hidden pipework properly flushed and then pressure tested. It would be wise do a chemical clean to loosen up any hard deposits in the week or so leading up to the flush.

After the flush please do get it pressure tested as you are planning to convert to a sealed system. If the hidden pipework is clear, clean and tested then you can go ahead and use it. It's not ideal but I understand why you don't want to rip it out and we don't live in an ideal world so as long as you can be confident the pipework is sound, you can make it work. It's certainly not a job to just cross fingers and hope for the best!

 

[Jimboliana]

Stigster,
Spot on and good idea to pressure test it after. We have all the gear for pressure testing as well
One of the guys that will be doing it does work for me and is a qualified plumber so we are calculating the size of the rooms for the rads etc. and to size up the boiler. But it is always good to have other peoples opinions/views that may have had more experience with these things. He has a power flusher and as I say we were going to take the rads off and power-flush the pipework.
He doesn't seem to think I should need to add any chemical before the power flush as he has said the power flusher should strip it back to bare copper?

 

[Stigster]

I suggest the pre-treatment because you already appear to have some blockages going on and also that microbore is not the easiest thing to flush. Powerflushing works on high flow rates rather than high pressure so if the water cannot flow it cannot clean. A high throughput of water is already limited by the small 8mm tube (8mm is the external diametre so the bore diametre is even less). Putting a cleaner into the system for a few days will hopefully break down or loosen these blockages and allow the flush to do its job properly. All learned through personal experience after being told by several people "you can't powerflush microbore!"

It's not essential but it's an inexpensive and easy thing to do. It's what I would do in a system like that.