General questions; planning, and ‘before you
start’.
Q. How long does it take to power flush a system
thoroughly?
A. It will vary from house to house, but generally about
5+ hours for a three bed house with a vented system,
but less time for a sealed / combination boiler system,
because you don’t have to cap off the cold feed and
expansion piping.
You can save more time by using a CP2 pump head
adaptor to get connected faster, and also by filtering the
water as you go with a CombiMag power flush filter.
Q. How big a heating system can you use a Clearflow
pump on?
A. Obviously this will depend on what model Clearflow
you have. If you have a CF30 Classic, then you can tackle
systems up to 20 radiators with the right technique.
Follow the normal procedures for systems up to 12
radiators, but tackle larger systems in sections. For
example, with a twenty radiator system, close off ten
radiators totally, and flush the rest of the house normally.
Once done, close down all the flushed radiators, and
repeat the procedure on the rest of the system.
The CF40 Evolution has a significantly higher flow rate,
and so up to 25 radiators is a reasonable prospect, and
larger if you section the system.
If you regularly work on larger systems, you’ll really
appreciate the extra performance of a CF90 Quantum2,
which will get more debris from any given system (even a
small microbore one!)
Q. Do you need to drain down the system before you
start?
A. No. You only need to run some water out of a
vented system to lower the water level in the feed and
expansion tank, so that you can cap it off.
Q. Can you power flush a sealed system?
A. You certainly can - in fact you can ONLY power flush a
sealed system. Why do we say that? because any system
that you power flush
must
be sealed (even if that is for
the duration of the power flush only in the case of a
vented system).
That is why you must ‘cap off’ the cold feed and
expansion pipes of systems that AREN’T already sealed,
to prevent the high flow of water of a good power
flushing pump from forcing water up into the f&e tank
and overwhelming the tank overflow. Naturally you
remove the temporary caps after you’ve flushed the
system.
Obviously you don’t have a vent or cold feed pipe to cap
off with a sealed system, and so the power flush won’t
take so long. When you break into the sealed system
wherever you have chosen to connect your power
flushing pump, you’ll lose the normal system operating
pressure, and will have to re-pressurise the system with
the filling loop after you’ve finished the flush.
Q. If I power flush a sealed system, which has a
pressure/expansion vessel, do I need to take any special
precautions or disconnect it?
A. No, not if you are using Kamco flushing chemicals.
They will not cause any problems with the diaphragm of
an expansion vessel.
Q. Do you need to be Gas Safe registered to power flush
heating systems?
A. You don’t have to be Gas Safe registered to power
flush a heating system. As long as you are NOT working
on the gas train, then you don’t need approval, BUT be
Frequently asked questions about the use of Clearflow power flushing pumps
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