However, this will not clean the gravity hot water
pipework. Some engineers will re-locate the Clearflow
pump and connect it across the cold feed and expansion
piping to force water through the gravity hot water
circuit.
If there is one radiator on the gravity hot water circuit, as
is sometimes the case, or a towel rail, you may be able to
connect your Clearflow across the tails.
In and ideal world, you would disconnect the gravity hot
water pipework at the boiler, and then power flush the
hot water circuit separately – but this is far from easy in
a back boiler fired gravity hot water system.
Q. Can you flush a very old system which has
passivated steel or stainless steel piping, such as
Truweld or Gecol?
A. Yes, you can, but we advise extreme caution, and you
should always point out to the householder that you
cannot guarantee that there will not be any leaks. These
pipes were ‘stop-gap’ materials used during a period
(late sixties/early seventies) when there was a copper
shortage, and were not expected to have a very long life.
The passivated steel tube (similar dimensions to 15mm
copper tube) was fabricated from sheet steel, folded
over, seam welded and galvanised. Thirty years later
it has generally corroded internally such that it is on
borrowed time. Some engineers refer to this steel
pipe work as “Birmingham” tube, as one source was a
GKN company in the West Midlands. Look for tube of
an aluminium / silver colour, and connected with soft
soldered copper joints – and avoid it. Another clue is that
it is magnetic – copper and stainless steel aren’t.
The stainless steel tube supplied at that time was of a
low quality and is prone to pitting corrosion, and again is
on borrowed time.
If in doubt, do not power flush the system. If you accept
the job, use HyperFlush instead of PowerFlush FX2 – and
always ask the householder to sign a disclaimer!
Q. Are there any other systems I should treat with
caution?
A. Look out for low quality ‘Type Z’ 15mm copper
tubing of continental original, also supplied at the time
of copper shortages. It was prone to pitting, and had a
very thin wall thickness, such that it could not be bent.
You can recognise it because the manufacturers kindly
printed a red line along it. Another clue will be the lack
of any bends (only joints) in the copper piping.
Q. Can you power flush systems with old plastic piping
(PEX), which didn’t have the ‘barrier’ included?
A. You can flush such systems exactly as for any other
system, BUT you’ll probably find they are very heavily
sludged. Most plastic piping now includes a barrier
layer, to stop air diffusing through the wall of the pipe,
and only ‘barrier’ type pipe should be used for heating
systems.
The water in pipe without a barrier layer will always
be more oxygenated (=more conducive to corrosion)
and therefore systems with the non barrier pipe can be
expected to corrode faster even with a good corrosion
inhibitor present. The inhibitor level should be checked
every six months rather than annually.
Unless the system is re-piped it is probable that it will
need to be power flushed every few years, and it is
prudent to warn the householder that this is the case.
Other systems?
Q. Can you power flush a system with plastic piping,
such as Hep2O?
A. Yes you can. PowerFlush FX2 liquid and HyperFlush
can be used on plastic pipework systems, and will not
damage either the pipework, or the ‘O’ ring materials.
Q. Can you power flush under floor heating systems?
A. Yes you can. Underfloor heating systems are piped in
plastic tubing, and either FX2 liquid or HyperFlush can be
used on these systems, and will not damage either the
pipework, or the ‘O’ ring materials.
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