Power flush blocked microbore?

dgwilliams

My CH system is 25 years old and has 15 rads connected with microbore piping. The rads have double entry valves on one end of each rad. 6 of the rads are not working. A plumber has taken the rads that are not working off and says they are not blocked and the blockage is in the pipe work. He has recommended replacing all the valves with ones on each end before power flushing. Says cannot power flush blocked microbore system with current valves. Estimate £1250. Do you agree?

mw84_2

He is correct in saying that a ch system with twin entry valves cannot be powerflushed. I would try changing the pump first, if that doesn't work then the valves will need changing. Have you asked for other quotes?

One other point, Powerflush is a trademark product and should come with some kind of guarantee that the system will not block up again. Make sure that the plumber is going to use this Powerflush and not a cheaper version (usually called jet flush). Hope this helps!

Boilercare

Powerflushing is a generic term for using a high flow-rate pump and chemical combination to restore circulation to a restricted central heating system.

A microbore system with twin entry valves can be powerflushed, but not very effectively.
My company carries out powerflushing, but we would advise that you DO NOT use an acidic powerflushing chemical with microbore systems, irrespective of whether it has twin entry or single entry valves (there are non acidic versions on the market that would be suitable). This is because you cannot get an adequate flow-rate through the pipework to neutralise the acid afterwards. During the process of powerflushing, carbon dioxide is given off, and if not completely neutralised, will result in continuall gassing of the radiators.

Before you go to the extent of powerflushing, I would advise that you try a non acidic restoring chemical such as Sentinal X400 that can be added via the header tank, and left in the system for up to 1 week before flushing out simply by draining the system in the normal way (the draining and refilling will need to be done 3 - 4 times to get all of the X400 out of the system).

If this does not resolve the problem, then consider powerflushing, but get some additional quotes as your cos seems a bit on the high side. Also get your plumber to seperate the cost of the powerflush from the valve replacement (which should now be thermostatic radiators valves that he is installing to comply with Part L of the Building Regulations). Our average charge for powerflushing is around £420.00 + vat, but bear in mind that different areas of the country vary.

Dave Hickey

dgwilliams

I have tried DS 40 and also removed and cleaned out some of the rads - they had lots of black sludge in them. Only one the upstairs rads is not working now and this has not worked for along time. It is the 3 downstairs rads that puzzle me. They warm up briefly when I first put the system on after draining it down, but then they cool down and dont heat up again afterwards. Is this likely to be a problem with the pump?