Andrew Gabriel wrote:
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)?

No access panels. I think the main problem is that there is no separate
drain point and the lowest accessible point to drain it is the cold water
inlet which is about 18" up the side. I suspect the only way to do this
might be to syphon it down with a hosepipe inserted in the top but that's
going to involve disturbing quite a lot of soldered pipework. :-(

Tim