What do cold water tanks actually do?

[TwoPlAnKs]

There are two water tanks in my house. One is full of hot water. The gas boiler heats the water and pumps it into the tank. The tank has an electric water heater in it which has been used once when the boiler broke about 15 years ago. This is attached to a shitty little pump which pumps hot water to the taps in my house. Its quite a sensible, and I assume, normal arrangement which provides hours of delightful showers and hot water.

The other water tank is in the loft. Its a big black sqaure thing. Cold water goes in the top and comes out the bottom. However, it seems to serve no purpose. The water that comes out of the cold water taps is mains pressure and that tank doesnt even have a pump on it. When the mains water gets cut off because of a water main bursting or whatever, we still have hot water for ages after but no cold water. But, the tank makes watery noises when you use water in the house.

So wtf does it actually do? Cold water tanks seem like quite a normal thing to have, we cant be the only ones. But this one seems to serve no purpose. Anybody know?

We don't have water meters in Scotland btw, the costs are included in the council tax and there is no reason to price us into using less cos we have loads spare, being mostly empty and very wet and all. Just in case that makes any difference to any plumbers who have only worked on systems with meters etc.

[Mule]

It's for storing dead rats in.

[TwoPlAnKs]

It's for storing dead rats in.

ah now you tell me. i've had the fookers lieing around cluttering everything up

[Over Carl]

Reminds me of gcse biology - we were given agar dishes and told to put random samples on but no mud as it could have tetanus or something. Everyone got dirt and stuff and got little bits. My dish was absolutely covered. Teacher asked wtf I put on there - I told him water from the tap. They checked it out and found a dead pigeon in there.

Anyway, back on topic, we have one but it isn't plumbed in anymore. I've also wondered why they would be considered a good idea.

[Jack-daniels]

This Explains All

[Freddy]

I thought the tank was placed high to add a pressure drop to showers etc.?

[rmj2663]

It adds pressure to all hot water outlets by being high and also acts as a reservoir for the hot water tank, and the central heating if its not a pressurised system. Twat in my house before me decided to locate it in the airing cupboard just above the hot water tank. This, while avoiding it freezing when in the loft, now leaves me with a trickle of hot water from all taps. It takes fookin hours to fill a bath now. Really do need to lift it to the attic again.

[~G~]

I always assumed the were called HEADER TANKS....

They keep your central heating system full and add water as needed....

Also add pressuer to hot water feed....

EDIT:rmj2663 beat me!!!!

[Welsh Pete]

I too have no idea dwhat they do...but I had great pleasure in tipping mine when the combi was installed as our cylinder, cold water tank and header tank were all removed...nice airing cupboard now!!!

[TwoPlAnKs]

It adds pressure to all hot water outlets by being high and also acts as a reservoir for the hot water tank, and the central heating if its not a pressurised system. Twat in my house before me decided to locate it in the airing cupboard just above the hot water tank. This, while avoiding it freezing when in the loft, now leaves me with a trickle of hot water from all taps. It takes fookin hours to fill a bath now. Really do need to lift it to the attic again.

aha, i get yah. so the weight of the cold water in the tank is constantly pushing on the hot water tank to both refill it and increase its pressure?

genius stuff

thanks everyone

[B B Leo]

its a cold water storage tank m8.
it keeps a feed of cold water to ur cylinder. and also feeds the cold water to ur bath, basin in the bathroom and also ur toilet.
its has good points and bad point the way ur system is
but to remove it u would not a new combi boiler £600 or so

[Roty]

its a cold water storage tank m8.
it keeps a feed of cold water to ur cylinder. and also feeds the cold water to ur bath, basin in the bathroom and also ur toilet.
its has good points and bad point the way ur system is
but to remove it u would not a new combi boiler £600 or so

Not neccesarily m8, it probably is the hot water cylinder fill only, as said earlier, as you use hot water this refills the cylinder ready to be heated up again by your boiler and also gives you pressure needed at your hot water outlets. An easy way to know is to check the pressure at your kitchen taps and see if you get the same force of water coming out at your other cold water outlets, if you do all cold water outlets are mains fed, if not don't drink the water from anywhere apart from your kitchen tap, as it's tank water and will be probably full of bugs and sediment. There may also be a smaller tank which fills your central heating.

[TwoPlAnKs]

its a cold water storage tank m8.
it keeps a feed of cold water to ur cylinder. and also feeds the cold water to ur bath, basin in the bathroom and also ur toilet.
its has good points and bad point the way ur system is
but to remove it u would not a new combi boiler £600 or so

yeah this one doesnt feed any taps afaik, all the cold taps are mains pressure.

i'm not arsed about it. its not my house and even if it was, the plumbing here is excellent so i'd not want to change it anyway. its just bugging me not knowing what it does.

another question - if it does exist purely to feed the hot water tank, but everything else is fed direct from mains, then why cant the hot water tank be fed direct from mains? would that not give mains pressure hot water or am i thinking too simply about the issue?

[Eddie101]

The hot water is fed via a tank simply for storage (low pressure areas normally) ,the hot water tank is simply a thermal storage .The system works via gravity as in approx 1/2 lb of pressure per foot of head .One thing that you have that someone has not with a combination boiler is stored hot water ,if the streets water supply stops you have 45 gallons of water in storage (non drinkable) for washing etc .As for the hot water getting fed directly from mains that is referred to as being unvented ,and can be done using a longer but smaller sidewinder in the cylinder which cold water runs through ,and using the tank itself as the heatstore for the central heating water (the different systems switch the use of the cylinder) it also requires pressure relief valves and pressure vessels.There are a few different types of unvented thermal stores such as megaflo and combi-mates ,limited in use obviously with the pressure of the mains supplying the house .

You stated when the tank was filling your cold water tap depleted ,the low pressure is probably the sole reason for the tank in your attic .

[TwoPlAnKs]

You stated when the tank was filling your cold water tap depleted ,the low pressure is probably the sole reason for the tank in your attic .

did i? cos it doesnt really. the pressure is pretty high out of our cold water taps which is part of why i am confused

cheers for all your info though, and to everyone else who has replied

edit: by "high" i mean we have 2 upstairs showers that can both run at the same time without pumps or water heaters or anything on them, they just work. could that be part of the reason for the tank in fact?

[B B Leo]

Not neccesarily m8, it probably is the hot water cylinder fill only, as said earlier, as you use hot water this refills the cylinder ready to be heated up again by your boiler and also gives you pressure needed at your hot water outlets. An easy way to know is to check the pressure at your kitchen taps and see if you get the same force of water coming out at your other cold water outlets, if you do all cold water outlets are mains fed, if not don't drink the water from anywhere apart from your kitchen tap, as it's tank water and will be probably full of bugs and sediment. There may also be a smaller tank which fills your central heating.

with out seeing it its hard to judge. so its not feeding any cold taps just suppling you cylinder then!
lazy mans get out instead of installing a combi boiler or replaceing with a magaflow pressurized system which it the dogs dangles

[B B Leo]

did i? cos it doesnt really. the pressure is pretty high out of our cold water taps which is part of why i am confused

cheers for all your info though, and to everyone else who has replied

edit: by "high" i mean we have 2 upstairs showers that can both run at the same time without pumps or water heaters or anything on them, they just work. could that be part of the reason for the tank in fact?

are the electric shower of mixers?

[Eddie101]

did i? cos it doesnt really. the pressure is pretty high out of our cold water taps which is part of why i am confused

cheers for all your info though, and to everyone else who has replied

edit: by "high" i mean we have 2 upstairs showers that can both run at the same time without pumps or water heaters or anything on them, they just work. could that be part of the reason for the tank in fact?

Nope you didnt ,must have been half asleep lol .Anyways in scotland most of the pipes were replaced and still are being replaced from lead .You will probably find out the area your in at one time had a poor water supply which was upgraded .Also a lot of new builds still fit the tanks in as opposed to combi's basically for cheaper maintaining ( a lot less things go wrong) during the warranty period .Most bath taps in modernish houses with storage have a cold feed from the attic tank as well (any drinking well has to be mains) ,it also evens out the pressure in storage fed showers etc (same pressure at the cold and hot).

[TwoPlAnKs]

are the electric shower of mixers?

mixers i think. there is no electricty going into them, they are sort of like glorified taps really but slightly more thermostatic. they're ace actually cos they dont get hot and cold when people use other taps in the house which is nice. now you mention it, the bath might be fed off the cold tank cos its not as high pressure as the other taps.

i didnt realise there were so many plumbing systems to choose from. the house, and the system, are 15 years old in august if that helps. it was built by ashdale homes. i dont know how big they are but they are basically similar to bett homes or whatever, they buy land and build a heap of houses on it to sell on to folk. i am assuming they would therefore do stuff like this on the relatively cheap, since they arent too arsed about repeat customers but any expense on actually building the houses is munching into their profit margins.

the boiler has started making queer as fuck noises lately so i am looking forward to a cold shower any day soon followed by a nice big new boiler bill for the parents. that'll be fun

one ace thing about our water here is that things are peaty so its very slightly acidic rather than alkaline, so we dont get limescale. and it tastes nice since its essentially the same stuff that goes into scottish bottled water. i'm not sure what it was like when we moved in cos i was 4 at the time

who'd have thought pipes could be so complicated.