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Damo · Joined: 14 May 2003 Posts: 9 Location: Winchester, England

Hello
I have recently installed a Bristan 1901 thermostatic shower valve with rigid riser and 4" shower rose. (Previously I had a Mira 451 I think it was.) I have a combi boiler (don't know brand off-hand), and the info for this mixer valve says it should be okay with any type of feed.
Anyway, even with the shower thermostat turned all the way over for hot (i.e. no cold water mix), the water temp is only really warm rather than hot. I don't know if this is because the flow is fast, and hence the water is not being heated properly. Pressure is very 'high', and temp improves marginally when I reduce the flow rate. The temp of the water coming out of the hot bath tap is fine, and I am hoping that someone may have a suggestion as to how I may remedy this problem.
(Some 'flow reducing fittings' came with the kit, but I didn't fit them when I installed it. It said to install if presuure greater than 5 bar, but boiler showing only less than 1 bar.)
Any suggestions / ideas most welcome.
Thanks
Damian

thescruff · Moderator Joined: 03 May 2003 Posts: 4751 Location: Bath

The 1bar on the boiler is the closed circuit side and not the domestic water.

The boiler will depending on make model give about 10 l/min, the mains cold about 40 l/min and the cold needs to match the hot, maybe a prv will be needed.

The Briston valve should be adjustable for temp/flow control, possibly a small screw in the end of the handle.

thescruff Cool

Damo · Joined: 14 May 2003 Posts: 9 Location: Winchester, England

Thanks for the reply.
Will check instructions and handle this eve. I assume by temp/flow control, you are not referring to the obvious temp control dial on the front, which as I say is turned to full hot ?
Not sure what a 'prv' is either.

Damo · Joined: 14 May 2003 Posts: 9 Location: Winchester, England

Just found out that 'prv' it is a pressure reducing valve.
Two of these were supplied with the mixer, but I didn't install them. By the sounds of things then, perhaps I should install one on the cold feed ? Will this have an effect even if I have the temp turned all the way over to the hot?
Thanks

thescruff · Moderator Joined: 03 May 2003 Posts: 4751 Location: Bath

Yes you should fit at least the prv on the cold to balance the two,

The little adjusting screw is in the shaft of the centre spindel, normally you take the center screw out and insert a very long thin screwdriver to fine tune the flow temp, the handel just turns it on or off ( or at least it does on all the ones Iv'e fitted ).

If you have the instructions read through it carefully, and let us know how you get on.

thescruff. Cool

Damo · Joined: 14 May 2003 Posts: 9 Location: Winchester, England

Okay, thanks for the info, I'll give it a whirl soon and let you know the result. Perhaps I might try just adjusting the screw first, as to fit the prv I will have to remove the mixer valve and fit new pipes/connectors.

Damo · Joined: 14 May 2003 Posts: 9 Location: Winchester, England

Couldn't find agjustment screw you mentioned, and decided to try a poor-mans version of fitting the prv first, as didn't want to have to dismantle the valve again if I didn't have to. I had fitted an isolating valve to the cold feed into the shower, so I half closed this, and it has had the desired effect of making the temp hotter. I'm hoping that it is okay to leave it like this long term without any adverse effect on the valve / mixer unit. Of course when I adjust now for a cool shower, I loose pressure, but I guess that would be effect if I had fitted the prv also ?
Anyway, quick effective result, as long as it won't have repercussions elsewhere.
Thanks for comments.

thescruff · Moderator Joined: 03 May 2003 Posts: 4751 Location: Bath

By shutting the valve down you will reduce the volume and pump up the noise level, but not reduce the pressure.

In some hard water areas the valve will deteriorate rapidly.

By your experiment you have proved the problem is unequal pressure, fitting a prv should cure the problem.

thescruff Cool

Damo · Joined: 14 May 2003 Posts: 9 Location: Winchester, England

Okay Scruff, point taken, and I guess I should do the job properly anyway. It's just that having just installed the whole kit, wasn't in a hurry to undo all the work, (which I'm sure took me a lot longer than it would you). To install the prv, I have to remove the mixer from the wall, and I assume where there are compressions fittings using olives, (i.e. on hot/cold water feeds and from mixer to riser), that this pipework cannot be reused and I have to use new stuff?
Last question then (I hope), is it only on cold feed that I install prv? Two were supplied with kit.
Thanks
Damian

thescruff · Moderator Joined: 03 May 2003 Posts: 4751 Location: Bath

Not sure what you have but turn the isolating valve off, and insert the prv anywhere between the isolating valve and the mixer.

By prv I don't mean the coloured restrictor rings that come with the shower, its a standard fitting from your local merchant cost about 12quid, just do the cold and adjust it to about 1.5 bar, some are preset at that pressure.

To fit you only need about 200mm of straight pipework for access, and no new pipe or fittings should be needed.

thescruff. Cool

Damo · Joined: 14 May 2003 Posts: 9 Location: Winchester, England

Aah, I misunderstood you. I thought you were referring to the restricting rings you mentioned, which should be fitted into the 'arm' of the mixer (don't know tech term) where the feed pipe joins it. Good job we clarified that then.
So, my next question is now are there different types of prv, and if so should I get a specific type?

thescruff · Moderator Joined: 03 May 2003 Posts: 4751 Location: Bath

Theres loads a different sorts, pop into Plumb Center on the industrial estate and ask for a 15mm PRV, cheapest they have about 12/15 quid.

15mm being the pipe size to the control valve?????

Mark and cut the pipe insert valve and do the nuts up 30mins top.

thescruff