What is involved in a power flush?

[JBR]

I've booked a power flush for next week, and would like to clarify what it includes.

The engineer told me that the radiators would be 'vented', but I'm not sure exactly what this means. Is it a good idea to remove each radiator (or at least disconnect it) and flush it through separately? Clearly, I'm no expert but I would have thought that flushing through the connecting pipes would be unlikely to force water through the radiators via the TRVs and lockshield valves, even if fully open.

I was told it would take most of the day, which is encouraging in as much as they are likely to do a thorough job in that time, and the cost will be £550.

One slightly worrying thing is that I've read that a power flush can cause pin-point leaks. How likely is this?

 

[Terry lambert]

Untitled

• Terry lambert
• 5 Nov 2014
• 3

TRVs can stop an effective powerflush as they are very restrictive; I drain down and swap the TRVs for wheel heads/ lock shield valves first.

Pin holes do happen, but if they do, the damage was already done and a flush has just speeded up the inevitable.

You wouldn't normally remove the radiators to powerflush, unless they need taking outside and mains flushing if they are severely blocked.

By radiators vented, I can only assume he means bleed? Or that you have an open vented system

 

[JBR]

Thanks for this very useful information. The system is not open vented, so I'm sure he meant bleeding the radiators.

Hopefully, he will place protective covers under radiators in case of any leaks, and should they occur, I presume he will close both valves to the radiator. I should think that the leaking radiator would then need replacing.

I must ensure that he will put some inhibitor in the system. I take it that this is done routinely.

 

[ScottishGasMan]

You would expect after powerflushing that inhibitoer would be added.

The point of powerflushing is to clear the pipes and radiators with out the need to remove the radiators. However as above, TRVs can ve very restrictive, also so can certain pipes ie microbore, theres virtually no point power flushing microbore systems.

 

[vulcancontinental]

You would expect after powerflushing that inhibitoer would be added.

theres virtually no point power flushing microbore systems.

+1

 

[JBR]

Thanks again. Our pipes are 15mm so, presumably, not microbore.

All but one of our radiators have TRVs, but I'm quite capable of removing them. Can I assume that, if removed, that is equivalent to the valves being completely open?

As for the lockshield valves, I have recently balanced all the radiators (or, at least, I tried!), so I intend to make a note of how many turns (or fractions of a turn) each one is from completely off. Then when, presumably, they are all opened completely, I'll know how to re-set them afterwards.

 

[ScottishGasMan]

Replacing the TRVs with straight through valves for the benifit of a power flush will generally allow alot more flow through the radiator than the TRV even open full.

DOnt worry about taking note of balancing, the system should be rebalanced from scratch afterwards as the dynamic of the water flow will have changed. The person powerflushing should balance system after but rarely will

 

[loafer]

JBR Not you again! Have you got yaself some Bury (Lancashire) black puddings yet? I'm still trying to convert the Yerkies to the ways and thoughts.. cultured.. principled... cotton not wool.... but they are stoicly resolute in their ways. I managed to get an extra 50p outa one Yorkies hands the other week!!! With a pair of water pump pliers and a heavy sedative.

 

[JBR]

Replacing the TRVs with straight through valves for the benifit of a power flush will generally allow alot more flow through the radiator than the TRV even open full.

DOnt worry about taking note of balancing, the system should be rebalanced from scratch afterwards as the dynamic of the water flow will have changed. The person powerflushing should balance system after but rarely will

Thanks. Is the engineer likely to go to the trouble of removing all TRVs and replacing with straight through valves prior to the flush? I somehow doubt it. Is it something I should insist upon? I have 11 radiators and am paying £550.

 

[JBR]

They've just done the power flush. They were here from 0930 until 1530, although that included some time waiting for a colleague to deliver a new heat exchanger which they then fitted after the power flush was completed. This was not part of the power flush, of course, but was replaced f.o.c. under my maintenance and service contract.

They seem to have done a thorough job and flushed each radiator individually by closing both valves to all of the other ones. They also added inhibitor, which I would have expected, and bled all the radiators. I was very impressed that, afterwards, they checked that each radiator was warming up correctly.

One thing they also did was to inform me that three radiators (in the bedrooms) had the TRVs on the wrong way, which doesn't surprise me bearing in mind the previous occupant was called Roger the Bodger. They were 'one-way', as the arrows (that I had not noticed beforehand) indicated, and were attached against the flow. They informed me that this ought to be corrected but, after a short time, these radiators began to heat up as well, so I said I'd see how we got on with it and, if necessary, ask them to replace them or swap them round.

This is interesting, actually, as I thought that 'one-way' TRVs installed against the flow would not work properly. It seems they do work, but perhaps not as efficiently as they should.

Would you sort them, or leave things alone?

 

[vulcancontinental]

Would you sort them, or leave things alone?

The valves will let you know themselves by chattering to you.

 

[JBR]

Would you sort them, or leave things alone?

The valves will let you know themselves by chattering to you.

I haven't heard them. They've been like that for many years; perhaps they've lost their voice!