If it's an electric shower then it should be fed by mains cold water. You are not allowed to pump mains so the answer is no.
If, however, whoever fitted it fed it with water from your CW storage tank resulting in poor pressure then yes you can pump it. In this instance it should have an separate supply from the CW tank independent of all other taps etc.
In that case it is a reasonable conclusion (on a site unseen basis) that apparent low pressure coupled with it being teed off the bath supply means it is almost certainly being fed by the CW storage tank.
Most electric showers have a minimum pressure at which they will operate anyhow because they are normally looking for a mains water supply. You should check the product literature to make sure that this particular shower CAN be used with either a gravity fed (as you have) or a pumped gravity fed (as you would wish) supply.
Irrespective of the source of water however the shower should have a it's own water supply independent of all other taps etc. I'm starting to feel that this was not installed properly at all unfortunately.
This raises another concern. Was a separate RCD protected 6 or 10mm electric cable installed from the consumer unit to the shower? If the installer just used a junction box and connected to upstairs ring that's dangerous IMO and I would recommend that the shower should not be used until it's been properly looked at. Does the circuit have an isolator switch fitted outside the bathroom? Did the installer give you a Part P certificate for the electical installation in the bathroom? I'm not trying to frighten you - I'm just being cautious in view of my concerns about the plumbing aspects of this installation based on yourdescription.
So in principle it looks as though the answer is - yes you can pump the cold water supply for this shower but I feel you need a professional to come in and look at your present installation to give you definitive guidance. The correct solution is to feed cold mains to it however IMO. Others may support my view or have a different one of course so further posts in reply will be of interest to you.
just want to throw something into the mix here, i seem to recall reading somewhere that you cannot under any circumstances pump and electric shower, tank fed or not.
i forget the precise wording of the legistlation but it has something to do with permitting no more than one electrical device on any one plumbing circuit, so an electric pump supplying and electric shower is a no-no.
i am happy to stand corrected if this is not the case.
also aren't there some electric showers with their own integral pump? or do they all rely on water pressure alone? i guess all modern showers do rely only on pressure as they are all designed to run off the main.
JESSICA: seriously, rosebery is right - don't go near that shower until it has been properly looked at it could be an unthinkable situation just waiting to happen.
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