On Mon, 09 Jan 2006 14:03:02 GMT, (sPoNiX) wrote:

Currently taking the CH apart and updating various things. The system
and pipework are over 30 years old and we live in a very hard water
area.

Had to remove a section of incoming main (15mm) and to my astonishment
it was virtually limescale free. There was a very fine layer of
powdery limescale but you could wipe this off with a finger.

Also, removing a section of pipework from the radiator circuit showed
that to have only a very fine layer of magnetite. The water removed
from the rads had a slight dark "tinge" to it but nothing severe.

The pipework genuinely hasn't been touched in 30+ years. The previous
owner stated that he did nothing to the CH system apart from hoover
the boiler out every year.

I'm starting to think all this stuff about limescale blocking pipes is
a load of rubbish.

Kettles and appliances yes (I have seen that) but pipework no..I
assume heat makes the difference?

Has anyone any first hand experience of pipework becoming seriously
scaled up or is it a myth?

Can anyone explain why my 30 year old pipework is scale free?

sponix

You wouldn't expect to find scale in the cold water pipes. If you
think about it, if that were to happen, all the street mains would be
in severe trouble by now. The calcium and magnesium compounds in
scale come out of solution on heating and generally on the heating
surfaces, so you would expect to find it on the surfaces of the coil
inside the HW cylinder and possibly inside some of the pipes in the
near vicinity. On older systems with a direct cylinder where there
is no coil and the DHW circulates by convection through the boiler,
you would expect to find scaling of the boiler and pipework from it.

The water in the heating circuit seldom changes, so no significant
scaling there. If the system doesn't have problems with pumping over
or sucking down because of pump placement and pipework, then initial
dissolved oxygen, causing corrosion would be used up.

You might find that if you check the radiators, there is more
magnetite in these since the water is crossing radiators at a lower
speed at a given point than it will be through the pipes feeding them.
Hence material is deposited, typically in a triangular shape at the
bottom.


--

..andy