Reducing cold water pressure for mixer tap shower

[goosander]

Since my previous thread on mixer tap showers got a bit off topic, I thought it best to start a new one...

If I were to install a mixer tap shower (e.g. Mira Extra) to my bath which has mains cold water and gravity fed hot water, I gather it is unlikely to work well unless the hot & cold pressures are similar.

Do I need to buy an (expensive) pressure reducing/equalising valve, or can I acheive a similar result by reducing the flow to the cold tap by means of a partially closed valve/stopcock, or would that not work?

 

[swidders]

So you've given up on the electric shower

You could try a pressure reducing valve on the cold water - although this will most likely not work since it will probably not reduce the pressure sufficiently (1bar = approx 10m head of water to match the hot water pressure).

In simple terms, try the isolator as you suggest and see what happens. If no joy, at least it'll be in place for your electric shower

 

[goosander]

Not entirely, but its not my preferred option. It would certainly cost much more than I originally thought and would require a fair amount of uprooting of floor boards to route the mains supply.

Currently thinking the mixer tap shower is the way to go - as you suggest I can try using an isolator valve to manage cold water pressure and if that doesn't work I have two options:

Fit a pressure equalising valve.

Swap the mains cold supply for a gravity one - this would be a pain but less so than the electric shower.

 

[swidders]

Unless your cold water tank is at least 5m above the shower, I' give the pressure reducing valve a miss since I have yet to source one for you that reduces mains pressure to below 0.5 bar. (http://www.havelockcontrols.co.uk/sitedocs/44510039.pdf)

I would also be concerned about the strength of the shower you are likely to get from a gravity fed system anyway. Have you ascertained whether the flow of water would be sufficient from the height of the handset anyway (simple hosepipe connected to hot water tap will give an indication).

In the end, if you are going to have to run the cold water from the tank, a powershower will probably be worth the investment in time and money. http://www.plumbworld.co.uk/mira-vigour-power-shower-191-18176

Since, no matter what has been said, you sound as if you would be likely to do the wiring yourself, this would not require heavy gauge cabling back to the consumer unit. The whole deal (in materials) will not overshoot your budget of £200 by a huge margin. Given the cost of prv's and a thermostatic mixer and the pipework which has to be run anyway, which may not even prove to be satisfactory, a power shower sounds more cost effective and a safer bet.

 

[JohnD]

I have a gravity fed Mira mixer with 10m head (I have a tall house) and it is quite reasonable. I have another with about 5m head and pressure is rather weak though flow is OK.

If you have less pressure, a power shower from the tank supplies would be better.

 

[goosander]

Unless your cold water tank is at least 5m above the shower, I' give the pressure reducing valve a miss since I have yet to source one for you that reduces mains pressure to below 0.5 bar.

True, but I've seen pressure equalising valves that claim a working range of 3 - 150 psi (approx 0.2 - 10 bar).

Have you ascertained whether the flow of water would be sufficient from the height of the handset anyway (simple hosepipe connected to hot water tap will give an indication).

The shower in my ensuite bathroom is a gravity fed mixer shower, which whilst no power shower seems to manage a reasonable flow rate from 15mm pipe. The shower I want to fit over the bath would be at the same height so should have similar pressure but with the advantage of the hot water being fed from 22mm pipe (mains cold is 15mm pipe).

I'd estimate the cold water tank as being somewhere between 1 & 1.5m above the shower head. Not much I know but the existing shower is OK.

In the end, if you are going to have to run the cold water from the tank, a powershower will probably be worth the investment in time and money.

Maybe. I must admit I had assumed power showers would be too expensive, so hadn't considered one as an option - I will look in to this.

Can you run a power shower from a combination of gravity/mains supply, or would this give rise to the same problems as the mixer shower?

 

[swidders]

Power showers i've used only run from gravity supplies. The one I forwarded details of does not permit mains pressure.

Good luck with it all.

 

[goosander]

Thanks.

I've decided that an instant electric shower is out as it will be too much hassle to install, so I will go for either a mixer tap shower or a power shower and install a tank fed cold supply.

No doubt a power shower would give a better shower, but it would be harder to install as I would have to either run pipes through a stud partition wall and disturb the tiling, or live with exposed pipe.

Since this shower will be for the use of a lodger rather than myself and will be installed over a bath with only a shower curtain to keep the bathroom dry, perhaps it is better to go for a non power shower to limit the scope for 'accidents'? I've never used one myself, so I'm not sure how much water they put out.

 

[swidders]

a dilemma indeed - genuinely hope the isolator valve does it and saves the heartache.

 

[mixertap]

I've got a related question. I have a mixertap and shower attachment, but get problems getting the temperatures right. We are blessed with enormous water pressure, and so I only have to open the cold a tiny bit to cool things down. The hot comes off the boiler, but is still pretty strong. Is there a simple way to sort out this problem, or will I need to invest in some complicated kit? I'd really like to not lose all the pressure, since it's quite a 'power shower' effect.
Thanks in advance!

 

[Charnwood]

I have a mixertap and shower attachment......Is there a simple way to sort out this problem,

If, by shower attachment you mean something that shoves on the spout of the tap, no.
If you mean a bath/shower mixer with a diverter for bath or shower, no.

You need a thermostatic bath/shower mixer:

Start at around 120 quid.

Link to Google images of thermostatic bath/shower mixers.