Well, we surmised it might be scale, because: no evidence of sludging,
and only affected a couple of rads, then predominantly one rad, and
eventually shutting off ALL rads bar that one seemed to shift whatever
It's suspected that a bit of scale broke off from within the boiler (it
was rather prone to kettling for a while) which is what then lodged
somewhere in the system. Can easily see how a flake of scale would end
up attempting to fit down a microbore pipe having come out the boiler on
rather thicker piping, and plug it enough to prevent flow to a rad or
two, depending on where it ended up.
There were no indications of anything else going on, no leaking
overflows, no hot feed tanks, rads were (when they actually all heated
up) hot at top and bottom, no sign of sludge coming out when system
drained and flushed, etc.
I still can't see a lump of scale managing to block the bigger bore
pipework (that's effectively about what goes in/out of the boiler) like
it could block microbore.
That level of scale/sludge would block up a small bore or microbore system.
As Andy has pointed out, micro has nothing whatsoever to do with the
blockage, and condemning a system fitted by the millions, because of one
poorly designed/installation/maintenance is quite foolish.
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, and condemning a system fitted by the millions, because of one
So of copurse condemiong all small bores systems because of one
poorly designed/installation/maintenance (example) is of course
Like hot air flowing downstairs?
You don't know what you are talikng about do you?
That's why IMM has a microbore sewage system. In pipe diameter, size
doesn't matter, and he is in a permanent state of verbal diarrhoea, he
flushes out his sludge frequently.
Gawd. Anyone who can't see that a small bore system isn't more prone to
blockage needs his arteries examining..
I can only comment that I have been using an 8mm system, in a hard
water area, unsealed for 16 years and sealed for two and there has not
been a sludging probleml, in fact very little deposit at all apart
from a small amount of copper swarf from the original installation
when I flushed it under pressure a year ago.
I've always maintained inhibitor in the system and tested it annually
according to the maker's recommendations, typically adding more every
If you want to do something specifically *not* to use inhibitor then
fine, but your costs in radiator replacement after corrosion will far
outweigh anything else.
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That's because there isn't a requirement.
The more likely scenario, if there has been a problem in a microbore
system is because it was not dosed with inhibitor. There should be
no need for repeated flushing.
.. and looked after properly as any heating system should be. The
only thing that one can say is that a 15mm system may run for longer
with sludge than a microbore system, but there is no reason why
sludging should happen in the first place.
I don't buy that. First of all the circulating water is very rarely
changed and there is only a limited amount of calcium and magnesium
compounds in the water to be deposited. Secondly, I've had an 8mm
system for 18 years and ther ehave been no problems other than the
original installer having used it for a couple of radiators where the
required flow rate would normally require 15mm pipe.
Thirdly, the more important issue is whether inhibitor has been used
and maintained properly. There is less tolerance to blockage by
sludge for obvious reasons.
There isn't any fundamental difference in the correct design of a
microbore system vs. anything else. Tube is tube. If the design is
done as it should be around maximum flow rates, I see no reason why a
microbore system would heat more quickly since the rate of transfer of
heat is not going to be greater. I suppose one could say that one is
more likely to use a larger number of smaller radiators and that
therefore the heat is being delivered into the house across a larger
number of emitters, but that is it.....
I suspect he is referring to the lower water content, hence the lower heat
capacity of the system components that may lead to radiator surface
temperatures rising more quickly. Much like using 15mm pipe instead of 22mm
pipe in your hot water piping gets hot water to the tap quicker.
On Wed, 19 Nov 2003 10:23:19 -0000, "Christian McArdle"
Possibly, but if you do the sums needed to size for whether additional
pressure vessel is needed, the water content in the pipes is small
compared with that of the radiators.
If you size pipes according to the CDA recommendations it is based
around a max flow rate in metres per second, and the rate of heat
delivery should not be any different. If you think about it, you want
the temperature drops to be the same either way.......
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