Power Shower

[battenburg]

Hi all, is it possible to install a direct hot water storage tank system in the roof with a pump for a power shower to work independently form the combo boiler I currently have? Or is there some other way of doing it?

 

[Riley]

More info required. Why can you not just run shower off the combi

 

[battenburg]

More info required. Why can you not just run shower off the combi

Hi Riley, I was told you can't run a power shower off a combi boiler as the pump would draw the water quicker than the boiler could heat it. I'm not a plumber and am confused by the differing responses I've had from tradesmen that have been round to look at it. Water pressure is ok but i wouldn't say its amazing.
I wondered if I could leave the boiler as is and run the shower off a cold feed storage tank in the attic with a heating element in it? Or would that work out just as costly as replacing the boiler for something that would be capable of running a power shower?

 

[Riley]

That is correct you can’t but why can’t you just run a normal mixer shower off the combi

 

[Ric2013]

Hang on, the OP has said 'independently'. He isn't trying to run a power shower off the combi. Probably the combi is already running one shower and he wants to have a second shower installed...

There are three main types of shower:

MIXER - runs off your existing hot water system, can be fed by a separate pump if you have a vented cylinder and want better flow
POWER - a mixer shower that incorporates a pump
ELECTRIC - fed only by cold water - heats the water as you use it
PUMPED ELECTRIC - fed by cold water but includes a pump if you wanted to take the cold feed from a cistern (for example if you have limited mains flow and need to use water faster than it comes into your house).

No reason you cannot have a hot water cylinder cylinder or a small water heater as well as a combi boiler in the same house if you want a second shower, and, once there's a cylinder, a power shower you can have.

Though if you don't mind the limited flow available from an electric shower, then that would be much cheaper than having a cylinder installed.

 

[steadyon]

1. As others have stated, you can run a non-electric mixer shower off a combi boiler. You cannot run an electric power from a combi for the reason your plumber gave you.
2. You would appear to have three options:
2a. Install an electric shower which heats its own water. Gives you some back up hot water if the boiler is out of action. However, you need to have heavy electrics run to it, and the shower performance is not going to pin you to the wall.
2b. Plumb a mixer shower with the cold coming from the main and the hot directly from the combi's domestic hot water output. Should give good performance and be cheap to run. No combi back up though. If you do go this route, I'd recommend a decent bar mixer such as a Bristan. They are fairly standard and easy to replace without construction activities. You would probably notice a temperature change if someone turns on the kitchen hot tap, and you couldn't run this and another combi fed shower simultaneously.
2c. Install a hot water store of some form. See below.
3. If you want the hot water cylinder in the loft, you are pretty much stuck with having an unvented hot water system.
3a. It can only be installed by a G3 registered person, and requires annual maintenance.
3b. You would need a minimum cold mains water pressure of 1.5 bar and a flow rate of no less than 20 litres per minute. 2 bar and 30 lpm would be better.
3c. You'd have to be sure the joists could take the weight. A 250 litre cylinder weighs over 1/4 tonne when full.
4. You can't heat a cold water storage tank per your post #3. An ordinary (vented) hot water cylinder requires a cold feed from a tank above it, probably not practical in a loft. It also requires the cold water storage cistern to vent excess hot water into.