bath shower mixer - unbalanced pressure

[gravytrain]

hi i need to replace a bath shower mixer. has anyone a product or solution to the problem of LP hot with mains cold(about 4 bar in our area). customer has really beautiful tiling round bath so doesn't want to disturb it by chasing into wall to fit shower valve or electric.

many thanks ... rob

 

[oldplumber]

if you can get under the bath stick on a tmv on the hot supply which supplies the bath/shower or replace the cold supply to the bath with a tank fed supply, then itll be balanced

 

[Alanka]

Fit a single-ended booster pump into the hot water supply pipe to bring the hw pressure up to nearer the cold mains pressure (it doesn't have to be anything like exactly equal!).

I recently did this in a flat with great success. I used a NewTeam Varispeed 50 single shower pump (about £153 including delivery). It's rated at 1.5 bar which should be enough for a decent hw/cw mix at the shower head. If the mains pressure still proves to be too high (unlikely), fit a pressure-reducing valve in the cold supply to the shower (or to the whole house if there are other pressure-related problems - e.g. water hammer).

 

[Puddle]

The above can work but is officially bad practice

Customer may have to turn hot on first to get pump going and then mix in hot water,even then cold pressure could stop flow from pump

As you are reducing flow through shower,mains may back up hot into tank and over flow,even if hose gets damaged/creased or head gets blocked up

Mains pressure may cause strain on pump and burn out or even split

Any damage caused by this set up will not be covered by insurance

Issue of cross contamination if mains turned off


just some points

Have seen it done and working ok...more luck than judgement

Have seen it cause a lot of damage and operation not that good

As plumbers ,we should be doing things right,start trying to do sub standard plumbing jobs to help out customers and it will end in tears and its usually ours


imho

 

[Robtheplumb]

Stick a Megaflo in, mains pressure hot or run a new feed to the cold from the loft tank = No Problem. Everything else is a bodge

 

[gravytrain]

hi thanks once again for your help

rob

 

[Alanka]

Puddle, while greatly respecting your experience and views on this (likely to be superior to mine), I'd nevertheless like to defend the use of a single-ended pump in this application.

1) Fitting a non-return valve on the hot water outlet from the pump rules out any possible backflow of high pressure cold mains water into the hot water system, however high the mains water pressure is.

2) Should the mains pressure be high enough, the NRV on the hot supply would be held shut, which would stop the flow of hot water via the pump and hence switch off the pump rapidly. You would then get a cold-only shower! If this happened regularly, a pressure-reducing valve on the cold mains supply to the shower would bring its pressure down to approximately what the pump can achieve (say, about 1.5 to 2 bar typically) and the problem would go away.

3) The hw NRV would completely protect the pump against high pressure mains water, as reverse pressure immediately shuts off both NRV and pump.

4) Additionally, fitting a non-return valve on the cold water supply to the shower mixer rules out any possible backflow of hot water into the cold mains, whatever happens to the cold supply.

5) Should the shower hose kink, or the shower head block up, the two NRVs would continue to protect both h and c supplies, as well as the pump. Complete blockage would, of course, shut off the pump anyway due ot lack of hw flow.

6) This solution to the problem avoids having to install a cold water break tank to feed a double-ended shower pump. In many poky modern flats there is scarcely room enough for the hot water cylinder or combination tank, let alone a second cold water cistern (as was the case for my particular customer)!

7) This solution also avoids having to install extra cold water pipe runs. Fitting two NRVs and possibly a PRV on existing pipework is relatively straightforward and takes up no valuable space.

With respect, I fail to see why this isn't an elegant, efficient, and safe solution to the problem, and I look forward to hearing your views.

 

[desrob]

Fit a single-ended booster pump into the hot water supply pipe to bring the hw pressure up to nearer the cold mains pressure (it doesn't have to be anything like exactly equal!).

I recently did this in a flat with great success. I used a NewTeam Varispeed 50 single shower pump (about £153 including delivery). It's rated at 1.5 bar which should be enough for a decent hw/cw mix at the shower head. If the mains pressure still proves to be too high (unlikely), fit a pressure-reducing valve in the cold supply to the shower (or to the whole house if there are other pressure-related problems - e.g. water hammer).

as puddle says bad practice and in my experience does not work very well,stupid set up'