Do You Think I Would Be Taking The ***...
Jobs & Education2 mins ago
No best answer has yet been selected by theren_911. Once a best answer has been selected, it will be shown here.
For more on marking an answer as the "Best Answer", please visit our FAQ.Sorry, just to elaborate. The Central Heating pump, which is usually in the airing cupboard, draws the water from this tank. The water is then heated in the bolier and then circulates round the radiators. Unsurprisingly, it does get filthy (especially if you have no cover on the tank).
Don't worry, this water is not used to fill your bath.
The tank is probably the overflow tank for the radiators - rest assured it is not anything to do with water that you would have to bath in or drink in any way. You could try putting chlorine tablets in it to purify the water, and this should also get rid of the smell.
If the cat has been going in there, is it possible that he has chased or killed a mouse up there? My parents had a revolting decaying smell coming from one of their cupboards, and it turned out to be a mouse that had crawled into a small gap and died. They never recovered the body, but the smell eventually just died away (no pun intended!)