On Tue, 21 Oct 2003 18:49:30 +0100, "M. Damerell"
wrote:


With all due respect I dont think that removing the rads and carrying
them out is the easiest way to flush a sealed system.

Well..... yes and no. I hadn't posted the full version of the
procedure this time because it is already in the Google archives, and
not all steps may be necessary.

If the system
was properly designed, (yes I know the OP called it a dogs breakfast)
the fill point and drain point should be on opposite sides. (i.e. one
on the hot flow from boiler, one on cold return). Then you can

switch off, release pressure at the release point.

connect fill and drain hoses, open drain valve, close pressure
release valve.

Turn on supply. Then by opening and shutting valves round the house,
you can send a fast stream of water through each rad in turn. This
should remove a lot of the sludge except if a rad is solidly blocked;
if so, then you will have to remove that rad and flush it.

I follow what you are saying and I did actually do this when
refurbishing my system with a new boiler. In principle it would work
well. However, there are a couple of points:

- If you have the filling point on one side of the boiler and the
drain close by on the other, then there is an easier flow path through
the boiler and you won't get that much water being forced through even
a single selected radiator. I fitted lever ball valves on each
side of the boiler - making sure a pressure relief valve was between
them. In any case this is a good plan because it avoids pushing crud
through the boiler. By adding another drain point I was able to
flush the boiler through independently as well. Then, as you say,
water can be forced through a single radiator to good effect. This
was my starting point, but I have to say that not a lot of material
came out or even much rusty water.

- I needed to replace the lockshield valves and TRVs on some of the
radiators (the lockshields were seeping and the TRVs had stopped
woring properly), and when I removed them I found quite a bit of old
copper swarf and a little sludge in the bottom of each radiator that I
investigated. It was really that which led me to systematically
take each radiator off and outside for a good flush through with a
pressure washer. This proved very effective at removing all of the
remaining crud.

I replaced the lockshield valves with Pegler Terrier types, which are
pretty good quality and there is a version with built in drain point
in the tail. Thus it's possible to drain a radiator before or
without undoing the unions.

With the radiator removed, the valves either side of the boiler can be
opened and mains pressure applied to the system. Each radiator
valve can be opened in turn at the location where the radiator is
removed and the pipework leading to it is flushed out rather than
anything being recirculated at all. I found that I got quite a bit
more copper swarf out this way and a small amount of iron crud as
well.

It's also worth mentioning that for a more complete job, fitting an
inline strainer on the boiler return is a good plan.


Refill as normal adding Fernox or similar sludge-remover. Repressurise,
run hot for a while as per instructions.

I found that this was worth doing as well.


drain, flush, refill adding anti-rust.

Very important and there is no harm in overdosing to some extent.


If the drain point is on the wrong side of the system, you will need
to cut pipe and insert an extra drain point. You may prefer to remove
rads.

If you do decide to remove and flush out rads, note:
1. When you undo the joint, water will ooze out. When you definitely
separate the pipes, it will gush.

That's true if they were full. Generally it is possible to drain
upstairs radiators through the pipework, although downstairs ones at
the unions. Hence the suggestion of using cat litter trays as they
will take the water from most sizes of radiator.


2. However carefully you tilt a rad to drain it, there is always a
little bit of mucky water lurking inside, waiting for a chance to run
out & ruin your carpet. Carry rads upside down, with ends plugged.

Yep. I used "condoms" made from small sandwich bags held on the
tails with rubber bands.



Making joints. I know that other posters use PTFE tape, I have had
better results with Fernox leak sealer (I have no connection with
Fernox). It comes in a toothpaste tube, you smear it onto the male
part of the joint, dont get it on your hands, bad for skin.


You can get PTFE liquid thread sealer which is also effective as a
substitute for the tape - probably similar stuff to the leak sealer.
Radiator tails often do seem to have looser threads than other
threaded joints. I've also found the thicker PTFE tape used for gas
(on yellow reels) to be good for this.


..andy

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