In article 6,
DerbyBorn writes:
Roger Mills wrote in
:

On 05/03/2014 15:43, DerbyBorn wrote:
A friend is having trouble getting his downstairs radiators hot.
(Upstairs it balanced down to a minimum)
A plmber has replaced the pump to no avail. Today he did a power
flush but he connected to a radiator flow and return. I had assumed
that flushing was normally done at the pump connectors.

If there is a blockage then I believe the pipes under the floor are
the problem.

Sould he be trying to connect the power flush into one radiator - and
the return into a different radiator?

Chances are that any blockages are *inside* the radiators rather than
in the pipes. Best way of dealing with that is to take all the rads
off and take them outside and flush each one out with a hosepipe.

Then flush the pipes (with the rads out) by opening one radiator valve
at a time until the water runs clear.

I am thinking that the lowest pipes are likely to be sludged. The rads had

Sludge tends to collect in the slowest flow parts of the system
where it drops out out the flow, which are the radiators.

This is easy to diagnose - if the bottom of the radiator remains
colder than the radiator's return pipe when the system has warmed
up to steady state, then that's because the radiator is sludged up.

OTOH, if the radiator return pipe is also cool, then that implies
that the radiator has insufficient flow, possibly because the system
hasn't been correctly balanced, or because of a blockage in the
pipework or valves. Blockage in the stop valve (used to balance the
system) is not uncommon because they are often only open a crack.
Fully opening to clear this and then resetting back to the original
position can sometimes solve that.

new TRVs fitted a couple of years ago so some draining down was done.

why the heck don't all plumbers fit and exterior drain point????

Some probably do, but this is the type of quality you are more likely
to find in a good DIY system. I have two low points, and therefore 4
drain points (fitted in both flow and return), and they're all carried
outside (even though the drain cocks are not all outside).

If you take the radiators off to clean, bare in mind the sludge is a
potent black dye if spilled on a carpet or similar.

--
Andrew Gabriel
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