Hot Water Cylinders

27 Nov 2006
Reaction score
United Kingdom
We are looking at a new hot water cylinder to replace ours that is leaking at the bottom.

Now.... there is a coil in the cylinder.... does this do anything if there is no immersion heater? As I understand it, the boiler heats the water and it is pumped up into the hot water cylinder, where it is stored until it is run off via hot taps (?? and radiators??). We dont have an immersion heater - the only way we can get hot water is by heating it via the oil boiler.

Am I right then in saying all our hot water cylinder does is store hot water??


Sponsored Links

Hot water from the boiler goes up into the coil, which it makes hot, and this heat is absorbed by the fresh water which is in the cylinder, and which you use to wash or bath in.

The water in the coil does not mix and does not come out of the taps. It is water from the boiler which returns to the boiler to be heated again. the circulating water contains (should contain) anti-corrosion chemicals.

The cylinder does not heat the radiators. but the water in the coil (and the boiler) is the same recirculatjng water that also goes round the radiators.

If you are having a new cylinder then it is a good idea to get one with an immersion heater. Then you can have hot water when your boiler is out of action.

The cylinder usually stores enough hot water for a bath, so it enables you to fill the bath quite quicky without waiting for the boiler or immersion to heat it as it comes out of the tap. this means that a cylinder can usually deliver more hot water, faster, than an electric shower or a combi, because it has been heated ahead of use. You can also use a power shower pump on a cylinder, to deliver hot water at tremendous rate that you cannot get with other methods.
Thanks JohnD... that makes sense... to OH, if not me... :oops:

Wouldnt the immersion heater be bought separately anyway?? Thats what they told him??
Sponsored Links
possibly, but it is screwed in (with a big spanner that the supplier might lend or hire to you). I would expect your plumbers merchant or DIY shed to sell both cylinders and immersions.

A long immersion will heat more water; a short one will heat less, but quicker. It is possible to get one with both a long and a short element, but they are very expensive.

Consider if your old cylinder was big enough to give you a full bath; if not, you may like to get a bigger one, but in that case the pipework will have to be changed to fit. If friends or neighbours knoew a good local plumber he should not find it difficult. Cylinders are made of very thin copper so it is possible to crumple or tear them if you are heavy-handed with the spanners, especially when it has no water in it.

The new cylinder will probably come with foam insulation. Get some pipe insulation for the hot pipes round it too (in stiff plastic foam).

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local