DIY Doctor

Shower replacement advice please

Postby Sammyfaye » Thu Dec 27, 2007 2:41 pm

Hi All,

I'm struggling to get my head around all the shower info so thought I'd ask here!

We have a Worcester Bosch 25CDi combi boiler and an electric shower at present. The shower does not have much guts so we were wondering what the solution is? We have a redunant cold water storage tank in the attic which could be plumbed back in if necessary. Would this cold water feed be able to run through a Triton T80si pumped or T90si electric shower?

I have also read about the mixer showers and thermostatic mixer showers which are compatible with a combi boiler. However, when the cold water and hot water taps run simultaneously, the flow of hot water is very poor. Therefore, I cannot see how such a system could provide us with a good overall shower pressure.

Any help or advice would be very much appreciated.
Many thanks,
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Postby marrtin » Fri Dec 28, 2007 2:35 pm

Frankly, the first thing I would do is get your local water company come and check your water mains supply. You should be able to combine a mixer with a combi and get an excellent shower. The water companies to save water reduce their mains supply pressure which often causes problems such as this.

You need to post to the central heating forum and ask confirm your model of boiler will work well with a mixer shower (it may not be powerful enough (my guess is it is)).

In theory, the T80 could if you find someone who could wire and plumb it up would work as you suggest, but if the water pressure is so poor as not to work even an electric shower, I would put the money you are going to spend on the pump towards sorting a new 32mm supply to your house. Means you getter better water to all taps as well as the best shower!!
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Postby ericmark » Fri Dec 28, 2007 4:52 pm

I don't have combo boiler but very similar system. Problem is you can't pump the water from a combo boiler hot water supply but if water pressure is a problem then an electric shower is also out so there are three ways which can work.
Use a thermostatic mixer unit like I do direct.
Store hot and cold water using a vented system i.e. cistern with hot coil and header tank then a duel pump.
Boost the water pressure before it goes into boiler this may be banned I have seen it abroad but not in UK and I don't think water boards will permit it?
Since all three require the thermostatic mixer unit I would buy unit and try it then look at other two only if not enough pressure.
One problem I had was with shower heads blowing gasket and then finding a replacement that would take enough water as my system turns off the hot water boiler if flow rate falls below set level. Combo boilers store some hot water mine does not. I think you will be surprised on how little water flows through a standard shower head again you will need a show head so buy one and temporary plum in and test pressure. In my house I found stop tap not fully on have you checked yours.

Only problem I have is valve a little slow acting so with lever type taps and washing machines if someone draws hot water I get splash of cold before flow rates reduces to match and splash of hot before flow rate increases again. Because it mixes cold with hot and boiler is only 27Kw with large shower head we notice higher pressure in summer than winter as the water is warmer going into the boiler in summer so more cold is added so pressure goes up. But much better than old electric option. My fathers pumped from cistern and cold water tank is better regulated as it takes preference to any other demand in house. So running a tap makes no difference to pressure. Screw type taps are not a problem as they take longer to open and close so thermostatic valve has the time it needs to regulate.

I hope that helps.


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