Replace electric shower with HW cylinder feed?

ed110220

We have an electric shower in the bathroom (no bath - the previous owner was an invalid and had it removed). Our hot water is supplied by a cylinder in a cupboard upstairs, heated by a gas backboiler.

As we have no bath and use a dishwasher for washing up, the hot water is only used for hand-washing, cleaning the kitchen etc ie very little.

It seems a waste to heat all that water and use so little. What are your opinions on replacing the electric shower with one running from the hot water cylinder? I was thinking it would be cheaper to run and also I could get rid of the hideously bodged conduit that the cable runs in through the hall downstairs.

I'm presuming it will need a pump as the shower head is higher than the cylinder.

diywhynot

ed110220 wrote: »

We have an electric shower in the bathroom (no bath - the previous owner was an invalid and had it removed). Our hot water is supplied by a cylinder in a cupboard upstairs, heated by a gas backboiler.

As we have no bath and use a dishwasher for washing up, the hot water is only used for hand-washing, cleaning the kitchen etc ie very little.

It seems a waste to heat all that water and use so little. What are your opinions on replacing the electric shower with one running from the hot water cylinder? I was thinking it would be cheaper to run and also I could get rid of the hideously bodged conduit that the cable runs in through the hall downstairs.

I'm presuming it will need a pump as the shower head is higher than the cylinder.

How much are you willing to spend? Can you DIY, if not, seek advice from someone who has seen the job or post some photos on here for speculation.

molerat

You should not need a pump if the header tank for the cylinder is higher than the shower head. The only difficulties could be the amount of work and mess installing the hot feed.

diywhynot

See you've posted about this before.

ed110220

diywhynot wrote: »

See you've posted about this before.

Sorry, this house needs a lot of things doing to it and I forgot what I'd posted about before!

The hot water cylinder is fed from a tank in the loft.

keystone

I just looked at the previous thread and it sems you may not understand how your HW system works. Sorry if this is teaching egg sucking. What you have is something which looks like this:



The hot water is heated in the cylinder by the boiler. As you use hot water the cylinder is refed from the Cold Water Storage Tank by gravity. The hot water is forced out of the cylinder by the "static head" which is directly related to the height of the CWST above the HWC. Open the tap, water flows and is repleced. The replaced cold water is then heated by the coil in the cylinder to provide further hot water.

So the pressure and flow rate at the shower head is not related to the height of the shower head relative to the HWC but it is totally related to its position relative to the CWST. Does that make sense so far?

To utilise this existing water supply system wit a thermostatic shower you will need to:

1. Fit a separate outlet to the CWST so that cold water is supplied to the shower independently of all other taps and drawoffs.

2. Fit a separate outlet to the cylinder for the hot supply for like purpose. This can be done by means of a flange in the top or side of the cylinder or it can be piped directly from the vent but you need to know what you are doing or you will draw air in.

The reason for doing this is so that you get a balanced supply of hot and cold water to the shower at the same pressure and that opening a tap elsewhere in the property will not cut off the shower supply.

You will probably need to pump it as you will only have about 0.25 bar static head and if you do then you must pump both hot and cold together in order to maintain the balanced supply. Under no circumstances should you connect the hot to the cylinder and the cold to the mains. You'll just give yourself a seriously underperforming shower arrangement.

HTH

Cheers

keystone

ed110220 wrote: »

Sorry, this house needs a lot of things doing to it and I forgot what I'd posted about before!

The hot water cylinder is fed from a tank in the loft.

It doesn't matter for one second. See my other post.

Cheers

keystone

diywhynot wrote: »

seek advice from someone who has seen the job or post some photos on here for speculation.

Some of us know what he needs to do to accomplish this tak without the need for pics or speculation.

Cheers

ed110220

Thanks Keystone, I had not realised that the hot water pressure was supplied by the cold water tank in the loft. I had thought about it briefly, but had presumed not as it seemed counter-intuitive to refill the hot water tank with cold water while the hot water was being drained and thereby cooling the hot water.

What you described sounds doable but would probably have to wait till the bathroom is redone, as I have to redo the ceiling anyway (replace the fibreboard with plasterboard etc) and the pipes can go in then.

keystone

ed110220 wrote: »

Thanks Keystone, I had not realised that the hot water pressure was supplied by the cold water tank in the loft. I had thought about it briefly, but had presumed not as it seemed counter-intuitive to refill the hot water tank with cold water while the hot water was being drained and thereby cooling the hot water.

The hot water comes out of the top of the cylinder the cold feed goes in at the bottom. So the hot coming out and the cold going in don't actually mix. You get a temperature gradient across the cylinder yes.

What you described sounds doable but would probably have to wait till the bathroom is redone, as I have to redo the ceiling anyway (replace the fibreboard with plasterboard etc) and the pipes can go in then.

If your cylinder is directly behind the wall where the shower is located it can be easily done without major works as al the pipework will be done in the cupboard containing the cylinder or in the roof. If its in a different location then some planning is needed but its straightforward and no need whatsoever for speculation.

Cheers

ed110220

Thanks for the explanation, I had imagined that the pressure of the cold water entering the cylinder would mix it all up with the hot water straight away but obviously not! I've never had this type of hot water system before.

The hot water cylinder is not directly behind the shower, it's in a built-in cupboard in another room with a bedroom in between, but it would not be complicated to run the pipework through the loft as has been done for the cold water feed for the electric shower.