Thermostatic shower problem

[Cubik]

Hi there,

I've recently moved into a house which is around 3 to 4 years old and there is a thermostatic shower fitted in the bathroom.

The only problem is that it isn't very hot - The dial goes from 0 to 9 and it only has warmth to the output between 8 and 9, with 8 being mildly warm and 9 being just warm enough to shower.

The water flow rate and heat from other taps is very good - The cold is very fast and the hot has a slower flow rate (but not bad by any means) The hot water is also nice and hot (too hot to wash with on it's own)

The hot water comes from a combi boiler which I assume is fed via the cold mains pressure (i.e no tank)

Anyway, is this just an indication of the fact that the shower is knackered and needs replacing? Or that the system is "inbalanced" in some way in that the cold water which has a higher flow rate is just "overpowering" the hot when mixed.

Basically my question is should I just get a new one fitted or are thermostatic showers usually fitted with some means of adjusting the input ratio of hot to water? The shower is made by Sirrus - Are they any good?

Any ideas (or suggestions as to an affordable make and decent quality thermostatic shower)?

Cheers

Cubik

[Andy Hall]

This may simply be that the boiler is not producing enough hot water, or it could be the shower.

At this time of year, the mains cold water is quite cold - 8 degrees is fairly typical.

It would be useful to know the make and model of the boiler.

You could usefully measure the flow rate and temperature from a hot tap. Use a container of a known size - e.g. a 5 litre bucket and time how long it takes to fill. THen you can work out the flow rate.

Now measure the flow rate of the shower. To give you an idea, a shower needs to be at about 40 degrees so you can work out how much cold is added to what the boiler is producing. Obviously if the flow rate from the shower is greater than from your hot tap it means that either a fair amount of cold is being mixed in or that it is simply passing through the boiler more quickly when feeding the shower, which also means that the water reachin the shower will be cooler anyway.

This will give you an idea of whether the limiting factor is the boiler or the shower.

I think it's worth doing this exercise before you rush off an buy a new shower simply because it could easily be that the boiler is the limiting factor.

In terms of new showers, I would look at Mira, Aqualisa, Grohe, HansGrohe.

.andy

To email, substitute .nospam with .gl

[IMM]

It is highly unlikely that the boiler is not up to it. If the boiler is not delivering the heat and flow for just one shower then the boiler is faulty in some way.

[Andy Hall]

Without knowing the figures, that is pure conjecture.

.andy

To email, substitute .nospam with .gl

[IMM]

A smallish combi can handle the average shower, unless a drencher is used

[Andy Hall]

It depends on what you mean by average.

One of my showers - Aqualisa with a standard valve, hose and standard showerhead (not one of the large drench types or multiple heads delivers around 20 litres per minute..

How would you suggest that a 9-11 lpm combi could deliver its needs when the cold water temperature is 5 to 8 degrees, the shower operating temperature is 40 and the boiler is specified to give a 35 degree temperature rise?

... or did you mean something akin to an electric shower..??

.andy

To email, substitute .nospam with .gl

[IMM]

The smallish combi will be running flat out, but it will deliver a good shower.

[Nathan]

I've got a related question. We're installing a new shower and combi boiler system: I've been told by the guy who's installing the boiler that we should definitely go for a manual separate hot/cold shower as these are far more reliable, particularly in hard water areas (london). Is he right? I don't like the idea of fiddling with the controls all the time and having the water go hot and cold.

Any advice much appreciated.

n

[Andy Hall]

If you buy a good quality one (Mira, Aqualisa, Grohe, Hansgrohe) then it will be fine, although with any shower, thermostatic or not, you will have to descale the head in a hard water area.

.andy

To email, substitute .nospam with .gl

[Andy Hall]

How? 9-11lpm is only about half of 20.......

.andy

To email, substitute .nospam with .gl

[BillR]

Its rubbish. I fitted the victorian style, as sold by Screwfix & others, to a small combi in a London flat and it great..

[BillR]

I had similar problem when I fitted Victorian style, Screwfix supplied, to a small combi boiler. The manufacurer was very helpful. Firstly they said to make sure the flow restrictors to Hot and Cold feeds were appropriate to the installation. (Several of these were supplied in the kit) e.g. cold main feed and combi hot feed. Then they told me of another adjustment which meant taking the valve off the wall and adjusting a large screw in the back. This altered the amount of HW flow in the valve and did the trick. The end user is very happy with the result. You'll need to find the install instructions for your unit and/or speak to the manufacturer.

[IMM]

You add cold to take the flow up and 10 litres a minutes is a good economical and environmentally friendly shower. I the USA local,utilities went around to each home and fitted flow regulators free to each shower giving a 8 litres/min shower. Few complained about performance. They saved building another power station, with the power saved from wasting unnecessarily heated water.

[IMM]

It will have to have an integrated pressure equalisation valve inside, otherwise he is an idiot for saying that. Mira, and others make mixer with them integrated. They can be fitted in the pipes before the mixer as a separate unit.

[Andy Hall]

Hang on a second. If the water going into the boiler is at 5 degrees and it uplifts the temperature by 35 degrees, that takes it to 40 degrees by my addition. This is shower temperature. Where is the scope for adding more cold?

10lpm is not much more than an electric shower and they are certainly disappointing. It may be environmentally friendly, but it's not much cop is it? If you are going to follow this line of reasoning then you might as well advocate not showering at all - that's even more environmentally friendly from one perspective but not that much from another.

.andy

To email, substitute .nospam with .gl

[IMM]

Electric showers are about 5 l/min. A combi will burn about 22 kW to get 10 litres/min. I know of no 22 kW electric shower.

10 litres/min shower under mains pressure is very good.

Lots of cop. People want the high pressure against their skin, the volume is not that important to them.

[Andy Hall]

10lpm is only 10lpm.

Generalisation. You can't speak for everybody.

A small volume rate under high pressure implies a shower head with small jets. This is not comfortable.

.andy

To email, substitute .nospam with .gl

[IMM]

Not a generalisation, that is what most people want.

[Andy Hall]

You've asked them?.. commissioned a Gallup poll? ... enlisted marketing help from Alastair Campbell?

.andy

To email, substitute .nospam with .gl

[IMM]

Read the section on water conservation in this months mag Selfbuild and Design.