shower flow restrictor

[petek]

My son/d-in-l. are having problems with the shower in their recently aquired house. The basic problem is that the temperature is impossible to control and despite many attempts on my part to rectify matters the problem still remains. It starts hot for a few seconds then goes cold then settles down at a temperature which is only just warm enough, and varying the temperature control doesn't have any effect. The shower is a surface mounted thermostic "Victorian" design (IYSWIM) manufactured by "Force 10" who have gone out of business. Coincidentally, they have just had a new combi boiler (Worcester Bosch) installed which has probably improved things slightly but still not satisfactorily. I have dismantled the shower head many times, replaced the o-rings, checked the thermostat capsule (OK), and greased all moving parts with silicone grease, to no avail. After searching UK-DIY, and reading other posts I am now wondering if a flow restrictor in the cold supply could be the answer. Does anybody have any thoughts on this and if it is the answer is it possible to obtain some kind of restrictor that would fit in the supply pipe where it connects to the valve?

TIA Pete K

[Andrew Gabriel]

You need a special thermostatic mixer for combi or multipoint water heater. These are very fast acting and are designed to handle high pressure cold and wide ranging and varying pressure hot. What you describe is typical of using an unsuitable thermostatic mixer such as one of the slow acting wax pellet types which varies temperature by varying the hot flow (which has little effect with a combi or multipoint, which just heats the water up more to exactly compensate for a reduction in flow).

[newshound]

I am now wondering if

I have a restrictor (gate valve) in my combi *hot* supply line to get the water temperature up enough to sinks & baths (the adjustment on the unit isn't enough, even with the supplied restrictor). Noisy, but it works. One of these days I'll get arount to putting in something more streamlined. I gave up trying to run a shower off combis because the temperature cycled too much on any water demand elsewhere, although I know plenty of people do seem to manage OK.

[petek]

Thanks Andy

Yes, indeed, its quite possible that the shower was fitted some years ago before combi boilers came along. Having studied the inside of the valve many times to try to understand its mode of operation, your explanation sounds quite probable. We have considered, in desperation, replacing the shower completely but the existing shower is surface mounted on a tiled surface and the pipe work is concealed beneath the tiles. I cannot find a new shower with matching hole centres for the hot/cold inlet pipes so installing a new shower means breaking off the tiles to get at the pipework and then re-tiling. Obviously we are reluctant to do this so I was looking for another solution e.g. flow restrictor in the cold supply. Do you think this would have any effect? Pete K

[David Hansen]

On Tue, 15 Jan 2008 15:14:49 -0800 (PST) someone who may be petek wrote this:-

What are the current centres? Many bar showers come with little adapters that might allow a little adjustment to the centres, say from about 130mm to about 170mm.

[John]

If you decide to restrict the flow (and I am not confirming this will help) then this may help:

have a Mira 415 Combi Mixer which is fine - but pulls too much water for my boiler to cope with in the winter so I restricted the flow (with a valve fitted to the hose connection - supplied by Mira)

[sm_jamieson]

,

I have a bar mixer (triton tyne model) and a pressure equalizing valve across the hot and cold inlets. The combination works perfectly, but I fitted the same valve in my last house without the equalizing valve and it was OK. It all depends on the behaviour of the particular combi you have. Simon.

[John]

I find that my combi puts out water that is extremely hot at first as some water has been sitting in the boiler and the thermostat possibly allows it to overshoot a bit. One this very hot water has been drawn off then there is a period of coolish water as the thermostat realises that the hot water has gone and the boiler needs to fire up again. It then settles down. Quite a challenge for a thermostatic valve I guess if this is what yours is doing. Also reducing the hot flow causes the water to become a bit hotter.

[John]

As others have said, it sounds like you've a mixer that's designed for low pressure from a header tank. The system (H&C) is now at mains pressure. There's two answers: Fit a pressure reducing valve in each line. This is not cheap but is most likely to work. Fit a flow restrictor in each line. This could be a throtling valve or a short length of small bore pipe. The latter will need a little trial and error but cannot be fiddled with. A pressure reducer will hold a set output pressure provided the inlet is above it's set point so variations in flow are reduced. A restrictor will drop a fixed proportion of the inlet pressure so any variations are passed through. Since your mixer is thermostatic, it should reduce any temperature changes. An isolating valve is always a good idea anyway.

John

[petek]

Thanks everyone. I'm rapidly coming to the conclusion that it will have to be a new shower and re-tiling etc. I can't get at the pipework to fit any type of in-line valve in the supply pipes, I was hoping that some kind of restrictor that I could just pop in the end of the cold supply (after removing the shower valve) would have been available and this might have had some effect.

I am also aware of the eccentric connectors that are usually supplied with new showers that enable differing supply pipe centres to be accommodated. Unfortunately, I still couldn't get enough adjustment to fit the replacement shower that I bought from B&Q a few months ago.

So..... it looks like a re-tiling job!

Thanks anyway

Pete K

[George Duff]

Before you go to the level of taking tiles off etc try checking that you don't have a sticking diverter valve.I had exactly the same symptoms as you and this was the cause. A quick check is ,turn your heating off until the radiators are cold then turn on a hot tap,check your radiators and if they are warming up then your divertor valve is sticking partially between hot water and heating. Worth a try,good luck. George