On/Off H/W in bath & shower

[the_ace]

My old dear's friend wants me to go and have a look at her bath/shower as she's getting hot/cold/hot/cold upstairs but the hot flow is fine downstairs.

Sounds to me like some sort of temperature reducing device gone wrong. I remember hearing of these being fitted in homes with small children or elderly where they could easily scald themselves.

Any ideas?

[dontknowitall]

Coincidentally, I posted this somewhere else earlier today.

It's not exactly the same problem, but might be the solution.

You'll need a water pressure gauge to measure the water pressure and a weir gauge to measure the water flow.

From earlier today ...

Just returned from a house where hot water flow is poor. They have a fairly large combi boiler but since installation (by other plumbers) the bath has taken ages to fill although central heating is fine.

Looking in the boiler the plate heat exchanger has corroded and water is leaking everywhere.

Before automatically fitting a new one, I felt some testing was required:

Mains water pressure is 3.8 bar. Water flow rate around 18 litres per minute. So far so good.

Hot water flow rate is 6 litres per minute (everywhere, not just bath).

Contacted manufacturers who confirmed my suspicions. They need a pressure reducing valve to reduce water pressure to 2 bar before it enters the boiler. Then when done, I can change old heat exchanger and service the boiler. The manufacturers tell me this should sort out the hot water flow as the boiler can cope with 2 bar but not with 3.8 bar and, presumably, will create the hot water flow as required.

As I said earlier, hope this helps.

[the_ace]

Thats good info. The problem this wifey is having is the hot water cutting out upstairs but not downstairs so i can rule out the boiler. It must be a problem with the plumbing upstairs.

I'll remember that one though as i'm sure it'll come in handy one day!

[david williams]

pump on what? you cant pump mains and if its a combi its all mains

[dontknowitall]

Oops! That was in reference to another thread! Thanks for pointing that out - now edited.

[the_ace]

Funnily enough i just spoke to the old dear in question (on the phone) i got her to try the taps downstairs and lo and behold they are suffering from the same problem!

She says the mains pressure is brilliant so i'm now thinking the restrictor could be the way forward as the manufacturer says max 3 bar.

Apparently its had the thermistor replaced too so i'll test the mains pressure and fit a restrictor. Failing that a new thermistor will be next, then check the plate heat exchanger for blockage.

PS boiler is Sabre 24 which is a Vokera Compact 24 with a different cover.

[Plouasne]

Funnily enough i just spoke to the old dear in question (on the phone) i got her to try the taps downstairs and lo and behold they are suffering from the same problem!

She says the mains pressure is brilliant so i'm now thinking the restrictor could be the way forward as the manufacturer says max 3 bar.

Apparently its had the thermistor replaced too so i'll test the mains pressure and fit a restrictor. Failing that a new thermistor will be next, then check the plate heat exchanger for blockage.

PS boiler is Sabre 24 which is a Vokera Compact 24 with a different cover.

I would not fit a restriction, but a pressure reducing valve to reduce the pressure to what the makers recommend

[the_ace]

The maker says between 0.5bar - 3 bar. 2.5 bar should suffice nicely, anyone recommend a valve?

Screwfix do a honeywell adjustable one - Honeywell 15mm Pressure Reducing Valve - Screwfix.com, Where the Trade Buys