installing a new hot water cylinder

[apachi]

Hi everyone, could someone please help.
i have reciently noticed that my hot water cylinder in my bathroom, has started to leak at the bottom, i have checked all the pipes that lead in and out if it and non of them appear to be the culprit, so i can only guess that it must be the cylinder itself (a hairline fracture or something). so i would like to have a go a replacing it myself. i am not a total novice at things like this but this would be the biggest job i will have done im my home. could anyone please give any advice on how to go about this, ie what needs to be done before removal, anythings i will need, any tips etc. my system is a single pumped CH with indirect vented cylinder with calorifier. the cylinder has 4 pipes leading to it, the flow to and from boiler into calorifier on the left, feed from above cold water cistern on right and hot taps feed on top.
cheers

 

[Softus]

Cylinder changes can range from easy peasy to utterly b*stardly, but for professional plumbers most are run of the mill.

The basic process is straightforward:

1. Isolate and drain down;
2. Remove old cylinder;
3. Couple up new cylinder;
3. Fill, vent and test.

...but there are many pitfalls, including (but not limited to):

Alterations to primary pipework
Making onto imperial pipe (if any)
Difficulty draining and/or filling
Sealing threaded joints onto poor tappings

If you have the luxury of a few days of planning, then measure up the cylinder and order one with exactly the same position of primary connections. Critical dimensions are (a) distance from base to lower primary (usually the "return"), and (b) distance between primaries. You might pay more, but it could save you a lot of time and hassle in obviating changes.

If you want more specific advice then post some photos of your airing cupboard. Not the the knickers, but the pipework.

 

[JohnD]

This will not make the swap any easier... but you if you are replacing it, you might consider measuring to see what is the largest cylinder you can conveniently fit.

I find it very handy to have a good big cylinder that will fill a great hot bath and still have plenty for other uses.

 

[Softus]

That's not a particularly 'green' suggestion, John, and I'd never recommend fitting a cylinder that's larger then necessary, because a well-designed system with modern boiler and a high-recovery rate pumped-primary cylinder should be perfectly adequate.

 

[namsag]

With the new designed cylinders the recovery is that good if you put hot water on before you start to draw a bath it not far off keeping pace with what gets drawn

 

[JohnD]

Maybe my old cylinder was a bit too small. In winter you could feel it running out just as the bath got full. New one is a bit bigger and doesn't do that. New one appears to be 44" high and 18" wide. That's why I think a bigger one is better.