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Andy Hall
 
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Default Fitting Thermostatic Radiator Valves

On Mon, 26 Apr 2004 09:00:34 +0100, Mr E
wrote:

I'm planning on replacing the standard radiator valves with thermostaic
ones during the summer this year. I've got a system in a new house with
small bore (10mm external diam.) pipe that drops vertically from the valve
about 30cm then takes a right angle into the wall (its the new kind of
construction with 'hollow' walls, plasterboard then a gap then the brick
wall). The downstairs rads all have drain valves fitted.

I've fitted new valves on radiators before, but that was on 15mm systems
with the pipes going all the way down to the floor and allowed more room
for manouvering etc.

I'm wondering if anyone has any tips how to proceed, especially with regard
to draining. I don't want to lift the carpet away, but don't want to risk
dripping the dirty water on it. How is this job done by the professionals
with a minimum of fuss? I once drained the system with small bore pipe
years ago and had terrible problems filling it again, getting rid of the
air took a lot of messing around.

Any advice appreciated.

Mr E


I have a very similar arrangement except in 8mm.

Since you have drain valves everywhere, that makes life easier in the
sense that you should be able to attach a hose and drain. However,
there are two kinds of drain valves - the better ones have an O-ring
around the spindle which is good at preventing escape of water along
it; then there are the cheap ones which don't and will piddle water
out.

So let's assume that the builders have been cheapskates and plan for
the worst. Heating water, because it contains iron compounds, will
stain indellibly.
What I do is to first of all cover the area in plastic sheet, run up
the wall. The disposable plastic sheets for decorating from DIY
stores are good. Then put newspaper down. Wrap pieces of old
towel around the pipes leading to the wall in case any water runs down
them. It stains walls too.
I then use cat litter trays from the supermarket under each end of the
radiator. Even with a drain cock, when you take off the valves there
will be some water left.

Hook up the hose and then you are away. Since you have drain cocks
everywhere, this is a great opportunity to flush the system at each
radiator position. You can do this each way by opening the valve at
each end of the radiator in turn so that water flows both ways. If
you have a sealed system, this is especially effective. Make a note
of how far each lockshield valve is open so that you can reset it.
Alternatively, you may prefer to just do the balancing procedure after
the plumbing is completed - it almost certainly won't have been done
properly when it was installed.

For the TRVs themselves, you can get 10mm versions, although they are
sometimes harder to get and more expensive. I used 15mm ones with a
reducing fitting. You can get small tail fittings which are 15mm at
one end - actually 15mm pipe that will go directly into the
compression fitting of the valve - and a 10mm female solder ring or
end feed at the other end. These look very neat when done.

I always buy Drayton/Invensys TRV4 valves. They last longer and are
better quality than the cheap ones. You can get a good price at a
plumber's merchants if you buy the lot in one go. Since it is a
PITA to change them, it's a false economy to buy the cheapo versions.

When you have finished, you can refill the system, venting the
downstairs radiators first. It's worth putting in some system
flushing product such as is made by Sentinel or Fernox and run it hot
for a few hours and flush again. You can check for leaks as well.
Then put in some corrosion inhibitor. There are gel ones that can be
injected into a radiator with a mastic gun. These are a little more
expensive than the liquid ones - I find it better to ignore the
instructions and to inject into an empty radiator before filling
rather than against the pressure of a full one. Alternatively, you
could plumb in a dosing point with a piece of 15mm pipe and service
valve arranged vertically somewhere convenient. This would allow
liquid chemicals to be used.


..andy

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