The POWERFLUSHING myth...
Why might your system need powerflushing?
Firstly, the answer the question I pose above is it probably doesn't need
powerflushing right now, particularly if a technician is telling you this is the
solution to a breakdown. Of the thousands of boilers I've fixed, I have yet to
need to carry out a powerflush to fix one.
Starting from the beginning, all the steel components in a heating system
(radiators mainly) tend to rust on the inside. The rust forms a black powdery
deposit (iron oxide I believe) which forms a gloopy sludge in water and
progressively accumulates and collects in the bottom of radiators, pipes and
heat exchangers. It prevents radiators from warming up in the centre and at the
bottom, it makes heat exchangers in boilers hiss, pop and bang (known as
'kettling') and it reduces the flow capacity of pipes. Therefore it is a Good
Thing to have none of this stuff clogging up your heating system.
Clearly it is best not to allow the stuff to occur in the first place and
this is done by the installer of the system adding a product called 'corrosion
inhibitor' to the circulating water. Even if he does this it tends to get lost
should the system be drained down (to move a radiator for example) or if there
is a minor leak on the system, which allows the replacement water to dilute the
inhibitor to such a degree eventually that it is effectively all lost. Then the
corrosion begins to build up.
Once you have a contaminated system, the iron oxide can be removed using the
process known as 'powerflushing'. This is where a large pump with a chemical reservoir
incorporated is connected into your system and to a drain, and then water with
one of a variety of chemicals is pumped around the system at high pressure and
high speed. The point of this is to lift all the sludge settled in the system up
into suspension in the water, when it is then flushed out into the drain. This
may need to be done several times while the pump is connected. It's quite a
basic process really but doen well is shockingly time consuming. It used to take
me a whole day (working alone) to cleanse a system to my satisfaction back in
the days when I used to carry out this sort of work. After cleansing and
rinsing, new corrosion inhibitor is then added to stop new corrosion occurring.
However, there is a problem emerging. I regularly hear anecdotes about
heating engineers called out to fix boilers pointing out system contamination
(usually by drawing off a water sample and showing the customer how black it is)
then claiming the breakdown has been caused by the corrosion deposits. The
customer is then told they MUST have a powerflush costing many hundreds of
pounds carried out before their boiler can be repaired. This is patent rubbish
usually as the breakdown will have been caused by something else (a component
failure usually), especially if the breakdown occurred suddenly, but it can suit
a technician very well to claim corrosion deposits are the problem when he is
unsure or unable to trace the real fault. Customers faced with this advice often
feel they have no choice but to go ahead with powerflushing but once the
flushing has been completed and the fault persists, they are told 'oh well it
needed doing anyway'... Which is sort of true really, but the customer has been
bounced into having a powerflush that hasn't fixed their breakdown.
It is technically it is hard to criticise advice to powerflush a dirty system but on the other hand
it is quite unethical in my opinion to do this instead of persisting and fixing
the fault, THEN advising a powerflush as preventative maintenance after the
fault has been fixed. In the decade or so I have been specialising in breakdown repair
I cannot recall a breakdown where I repaired it by powerflushing. In my experience fixing
the underlying failure ALWAYS gets the heating going again with no need for a powerflush to get the heat on. Powerflushing
may be advisable but it is rarely if ever, essential for getting the heat back
I'm afraid this has turned into a bit of a rant...
First created 3rd January 2015
Last updated 3rd January 2015