Replacing a cold water tank

[hjalfi]

I've just bought a new house. I think the phrase you'd use to describe the state of it is 'ungg'.

One of the many, many misfeatures I've found is that the cold water tank in the loft (which feeds the hot water tank and bathroom taps) is uncovered. What's more, it's been uncovered for a while, including when the previous owner decided to replace all the tiles. I believe the technical phrase to describe it is 'full of crap'.

What's more, I'm in a hard water area. A lot of the crap is inextricably embedded in the limescale. I think it's basically a write-off.

My question: do I actually need a cold water tank these days? I know that the purpose of the tank is to lower the mains pressure and to isolate the mains from the low-pressure system, to avoid the possibility of contaminated water getting sucked back into the mains. Couldn't the same effect be achieved with the appropriate pressure reduction valve fitted to the mains feed?

This would not only save me loads of space --- the cold water tank is vast, about a metre on a side --- but would simplify the plumbing no end and reduce the amount of crap in the water.

If this can't be done, and I actually need a genuine, physical tank, then what are the guidelines for how big it needs to be? The tank feeds the hot water tank, cold taps on the bath and basin, plus the loo.

[Hmm. Looking at my preview, I notice that my post has been 'edited'. Let's just say that I used a slightly more forceful word than 'rubbish'...]

 

[ollski]

My question: do I actually need a cold water tank these days? I know that the purpose of the tank is to lower the mains pressure and to isolate the mains from the low-pressure system, to avoid the possibility of contaminated water getting sucked back into the mains. Couldn't the same effect be achieved with the appropriate pressure reduction valve fitted to the mains feed?

Yes but you would also need all the other safety components that go with a sealed system running into a couple of grand.

 

[hjalfi]

[/quote]Yes but you would also need all the other safety components that go with a sealed system running into a couple of grand.[/quote]

Damn. What do these involve? Incidentally, it wouldn't technically be sealed, because I'd reduce the pressure to what the header tank is currently giving me, and keep the overflow vent.

Failing that, how do I know how big a header tank I need?

 

[Bahco]

If you are handy and can plumb , why not convert all your cold feeds to come directly off the mains.

Your tank would would then only be feeding your cylinder for hot water and you could probably get away with fitting a smaller one.

Make sure it comes with a byelaw 30 kit and do it as quickly as poss as you are washing in filthy water.
Better still, get shot of the cylinder and fit a good quality Combi.

 

[hjalfi]

If you are handy and can plumb , why not convert all your cold feeds to come directly off the mains.

That's a definite possibility; there is a mysterious pipe-with-a-valve in the airing cupboard that I suspect is the tap feed from the cold water tank.

However, given that I can't actually get into the bit of the loft where the interesting plumbing is --- nor would I want to, see my earlier comments about the stuff in the attic that the forum is forcing me to refer to as 'rubbish' --- I suspect the simplest solution is to just replace it in situ. Screwfix do a variety of complete kits.

Make sure it comes with a byelaw 30 kit and do it as quickly as poss as you are washing in filthy water.
Better still, get shot of the cylinder and fit a good quality Combi.

What's Byelaw 30?

And yes, I do want to get a combi... but the existing setup (gas back-boiler in a chimney downstairs, mysterious and no doubt very inefficient circulation loop taking hot water to the tank in the bathroom 10m away, heat exchanger there) is sufficiently complex that I'd rather like to get the place habitable before fiddling about with it too much!

 

[Bahco]

Tie up your ball valve and empty your tank by running the water off in the bathroom.
Clean out thoroughly and refill.
No sense replacing it if you are having a combi in the near future.

 

[hjalfi]

Tie up your ball valve and empty your tank by running the water off in the bathroom.
Clean out thoroughly and refill.
No sense replacing it if you are having a combi in the near future.

Already emptied --- I siphoned it out, actually, I didn't want to pull the crud into the pipes --- but I reckon it's uncleanable. Plus, the combi boiler is going to happen a fair way down the line; I've got a lot of other stuff to sort out first.