Dirty hot water mystery

[Tim+]

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

)

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 c*ck 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

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.

I want to know is, where the f*ck 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.

Tim

[Andrew Gabriel]

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)?

[Jules Richardson]

Are you sure the bottom of the tank's not scaled up, with the crap hiding on top (and the scale acting as a filter when you use the drain tap)? I attacked ours a couple of years ago after performance started dropping off, and probably the bottom ten inches or so of the tank was full of scale.

[Andrew Gabriel]

[Tim+]

The tank is only 3 years old and we live in a soft water area so I'm pretty sure that scale isn't a problem.

Tim

[Tim+]

> As you can see, only very lightly stained.

>>>>> What I want to know is, where the f*ck is all this crud hiding??

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

[Andrew Gabriel]

I have visions of having to remove the cylinder, so you can give it a good shake and sloshing out. And then compression fittings, so it's easier to do next time;-)

Also a good excuse to buy one of those colonoscopy cameras from Aldi/CPC/Maplin, if you haven't already...

[The Natural Philosopher]

I think the answer is this.

(i) switch of all heat input (ii) leave the hot taps all on full for as long as it takes. The constant water flow should in the end stir up the silt enough to get it all out. (iii) any silt left is probably too heavy to ever come out again so who cares?

[GB]

There's no immersion heater?

[Dave Liquorice]

How about the pipe joining the pressure vessel to the rest of the system?

[Brian Gaff]

But hang on a moment... If the source is now gone, assuming it was the cold supply, you should only need to clear it out once. However if its still happening you might need to worry about where it is in fact coming from or whatever you do will have to be done over and over. I guess getting the pollution analysed would be too costly?

Brian

[geoff]

In message , Andrew Gabriel writes

I noticed that CPC were selling one with a USB I/f for £20-30 a couple of weeks ago

(I bought a chainsaw - watch out world !)

[Andrew Gabriel]

I noticed Aldi have the standalone ones in (somewhere around £70, IIRC).

Aldi had those too, although the box was remarkably small so can't have been big ones.

[Hugo Nebula]

That's a fuggin' bit pothole! I particularly like the tyre marks right to the edge; is there a water board van in the bottom of that hole?

[Owain]

maybe they were flatpack?

Owain

[geoff]

They will be when I've finished

Yeah - dinky little electric chainsaw, but just what I need for my rampant bay tree. I'm not felling douglas firs

[Onetap]

The internal coil has probably failed; the crud is from the heating system.

[GB]

I thought of that, but surely the OP would be forever topping up his central heating system, and surely he'd have mentioned that? Assuming it's an unvented system, ofc.

[Onetap]

The pressure in the CH & the unvented cylinder would equalise, so there may not be a loss of pressure in normal use. He did say; "This always happens if I depressurise and repressurise the tank." The CH would leak into the tank when he had drained it, so this scenario sounds plausible.

[GB]

not be a loss of pressure in normal use.

sounds plausible.

Ah, gotcha!

The OP can test this hypothesis by depressurising the central heating circuit. If it fills itself up (from the HW tank), then you are right.