On Wednesday, 24 August 2016 06:52:06 UTC+1, harry wrote:
On Monday, 10 December 2007 19:56:46 UTC, Jimbo wrote:
I've been having a problem where our hot water gets
progressivly smeliier with an metallic smell - The last time it got
bad, I got around it by draining off the HW cylinder and cold water
tank, but it's starting again.

One thing I've noticed is We have a small copper cylinder
(about 10 ins high and 5 ins dia) which when the central heating
switches off deposits a small amount of water back in the cold water
tank - It's got SPARTAN Automatic Recovery Tank on the side of it (and
Bray Thermal Systems) and has an even smaller cylinder, with a screw
on top, on the side of it (10 Bar max operating pressure)

I'm wondering it this is the cause of my smelly water,
redepositing water from the CH circuit back in the cold water tank

You need to clean out the cold water tank finishing off with bleach.
Also clean out the pipework and hot water cylinder with a bleach solution by letting it run through from the loft tank.
This tank should have a closely fitting lid and be insulated to keep the water cool in hot weather.

The lid should be near airtight.
A vent can be purchased and fitted which has a screen to keep insects out.

This sort of problem is made worse if the throughput of water is small or the tank is over sized.

You might even find a dead bird in the loft tsnk if there's no lid.

I have just managed to down load your pix, it was very slow, took 10min.
I see you have a combination tank.
The problem with these is the water in the top tank is warmed by the bottom tank so creating the deal environment or bacteria to thrive. The insulation is in very poor condition.

You need to improve the insulation on the bottom tank and get insulation between the two tanks.
Also if the lower (hot water tank) spends long periods with no throughput or warm rather than hot this makes the problem worse.

If there are old/young people in the house, the situation could be health threatening.