In article ,
"Tim+" writes:
We have a pressurised HW system (an Albion Ultrasteel cylinder) with a
external 18L expansion vessel.

For some time now we've suffered from intermittant dirty water supplies
which we suspect was due to a problem with our water mains further down the
street (as manifest by the major blowout recently
http://i1052.photobucket.com/albums/...k/da49f87f.jpg )

Anyhow, our water supply (or at least our cold water supply) has cleared up
but we continue to intermitently get dirt in our HW supply which I've been
putting down to a HW cyclinder full of silt. If no water has been drawn for
a while (like overnight) the HW is visibly stained.

Today I thought I'd try and drain down the HW tank using the drain cock to
see what the water was like nearer the bottom of the tank (expecting it to
be really dirty). I filled half a bucket and poured it into our sink and
this is what it looked like
http://i1052.photobucket.com/albums/...EDFA1D3991.jpg
As you can see, only very lightly stained.

It seemed a bit pointless to carry on draining the tank so I repressurised
and and refilled the sink from the tap with this result.
http://i1052.photobucket.com/albums/...ED925ED3B6.jpg


What I want to know is, where the feck is all this crud hiding?? This
always happens if I depressurise and repressurise the tank. It's had a new
pressure vessel about 3 weeks ago after the diaphragm failed in the old one
so I know it's not the pressure vessel that's full of crud.

As I say, our cold supply seems okay but I'd really like to flush all this
crud out of our HW system but I'm mystified why water drained from the
bottom of the tank is so much cleaner than what's coming out the top.

I'm guessing it is in the bottom, but it wasn't stirred up when
you tried draining from the bottom. Filling just the bottom and
emptying it a few times might do it. Does it have any kind of
access panel such as immersion heater tap that you could look in
when it's drained down (or drained below the access panel)?

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]