Powerflushing of Microbore systems
By Derek Robertson – Southern Region Agent for Norstrom Group
I thought that when I took an early retirement package from my previous employer back in 2001 that I would be looking at an easy life, travelling the globe, sitting drinking coffee, reading the paper. Not a bit of it!. Education still needs to be continued. Training has to be carried out. Systems still need to be cleaned. Nothing surprises me in this Industry anymore and I continue to worry about the quality of some so-called plumbers/ heating engineers who really haven’ t got a clue about correct flushing methods or, despite training, don’t listen and still want to do it their way because that’s what they have been doing before.
DWTA say that between 50% and 75% of heating installers admit to using Inhibitors. Great! But let’s look at that statement in a more negative way. Between 25% and 50% are therefore NOT admitting to using Inhibitors! Where have these installers been all these years? Or are they just keeping their costs down and hoping they won’t get a problem during the warranty period. That might be more difficult nowadays with some boiler manufacturers giving 10 year Warranties on their heat exchangers. If you don’t look after the system then at some stage it is going to come back and bite you.
So let’s look at flushing procedures and in particular microbore. My own system at home has 8mm pipework but at least I haven’t got a problem with it!
Successful powerflushing can only be done by not cutting corners and certainly, if the heating system looks in a bad way, it is quite likely that some remedial work will have to be done before you even consider powerflushing a system. There is no point keeping leaky valves or rusting radiators because it is going to lead to problems at a later date.
I’m not teaching you good guys how to do your job but you really need to go round with the customer to point out the problems, or potential ones. If you show the customer you know what you are talking about you are more likely to pick up some extra work and at the same time save yourself the effort of having to go back on a non-chargeable recall. Call backs cost you money!
There isn’t such a thing as a typical system and what you do on one system may not work on the next.
I’ve found that out many times during my years in the Industry when dealing with corrosion and talking to heating engineers at training seminars across the country.
Many people within the Industry say that you can’t successfully powerflush microbore systems and some manufacturers will not guarantee their boilers where a new boiler if fitted to a system with microbore pipework. What do you do? Tell the customer that they will have to change all the pipework?
Unlikely you will get the job. Let’s look at the problem in more detail.
Admittedly, flushing microbore is not the easiest thing in the world and I always groan when either the dreaded M word is mentioned or I go out on site to do some one to one training and find 8mm pipework everywhere and an engineer who hasn’t surveyed the job properly. Let’s face it, if you get a request to go round and sort out a badly sludged up system with poor circulation, probably a noisy boiler and leaky rad valves and then find out it is on 8mm pipework to the rads don’t you just want to turn round and make a sharp exit?.
I think though that I have now found the best way to flush out a microbore system without problems.
It does take a while and the engineer will have to allow at least a day, day and a half to do it. Of course this also depends on the number of radiators on the system. I’ve known of engineers taking 4 days to do a system flush and being out of pocket at the end of it because they hadn’t done a proper survey.
Having recently failed dismally (exactly what I had expected with 8mm Microbore, twin entry valves and no drain off valves on the downstairs drop feed radiators) an engineer I was training on site has now had to go back, prior to fitting the new boiler, and flush it the way I suggested.
Remember that heat rises. We had no trouble heating up the individual radiators with the Norstrom Thermal heater. (The boiler was inoperative) Every radiator got hot eventually. So we had circulation everywhere. Come to flushing out. Didn't want to know! So how come we can get heat and circulation but not a flush. The answer is Heat.
Heat rises and starts to enter the radiators from the circuit once the circuit starts to heat up. It then completes the heating of the radiator and at the same time starts to permeate back into the circuit through the return valve.
When you have isolated all the radiators except the one nearest to where you are working then start to flush that first radiator which is still hot because you have just been circulating hot chemical water through it. The rest of the radiators have cooled down a bit but will still have hot water in them. By this time however the fresh cold water in the powerflushing machine being used for the final flush takes the line of least resistance and bypasses the radiators in the 22mm circuit instead of diverting into the 8mm radiator pipe work. If that water was hot it would rise and enter the radiator.
If you just open the next radiator and start to flush it the same way as the first radiator it is likely you will just be flushing clear circuit water and not the radiator.
Therefore, thinking about it, the only effective way to flush out the individual radiators after the first one has been done (If you are lucky enough to own a Norstrom Thermal unit) is to reheat the 40 litres of water in the Norstrom tank, get heat circulating through the one radiator (and circuit) and then open the drain valves to immediately flush that radiator (and circuit) until you get back to plain fresh water. This you would have to do for each radiator until all the radiators have been done. A supply of hot water from a hot water cylinder would reduce the time between each radiator flush otherwise you would have to wait for each heated tank to become available. This means that the average time for flushing each radiator would be around 35/40 minutes.
If you have the facility of a boiler (which we didn't recently) then the system can be kept reasonably hot and the boiler made use of to get the individual radiator up to temperature ready for a flush out. This will save a lot of time. Hot water circulation of each radiator through the machine prior to a final flush is therefore imperative.
The only other way is for the whole system to be drained, refilled, heated, drained, filled, reheated for as many times as it takes to get back to some semblance of clear water and hope for the best, alternatively a manual flush of each radiator in the garden which will again take time if done with the power flush unit because of the fact that you would need to alter the entry valves on each radiator and make up a connection, one top and one bottom diagonally and flush out each radiator for 10-15 minutes with the aid of the diverter valve.
If you are powerflushing with a smaller pump which does not have the velocity of the Norstrom
Professional range then you are really on a hiding to nothing and it is extremely doubtful that you will be able to achieve a satisfactory flush.
Any powerflushing however will be unable to remove 100% of the debris and astute engineers will also be recommending that a magnetic system filter like the Magmaster should be fitted on the system return to grab hold of any residues. That filter can be cleaned out on an annual service.
Happy powerflushing!
