My friend has asked me to install a bath/shower mixer in his council flat. The flowrate to the bath taps for the cold is twice that of the hot and I am want to avoid problems the unbalanced supplies will cause re using the mixer. It would be possible to fit a service valve on the cold supply pipe with a view to reducing the flow to that of the hot, but having checked the existing pipework I have found that the cold section is run in 22mm, but the hot section (from a combi boiler) is run in 15mm. This should be changed but should the local council be responsible for this work? I should add that my friend is partly disabled? Any views appreciated.
Bath/shower mixer in council property.
- Thread starter L_Plate
- Start date
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don't wanna say that the pipes are what you say they are. but i think they must be the other way. u can just tee off the h&c supply and fit a pressure reducing valve to the cws. but imo i would keep an electric shower as if the boiler goes tits up then the shower could be used as a back up.
Nath
Nath
No, they are not the other way, they are as I have described them, with the cold having twice the flowrate of the hot. I take the point about a PRV, though. I am just trying to establish whether with this installation, if not fit-for-purpose, the council have an obligation to replace the said section of 15mm pipe with 22mm? 
No chance of the council doing this for you-the purpose of the cold pipe is to supply water to the bath,which it does perfectly well-it's compatibility with the shower mixer is not really their problem or concern.
It would make little difference anyway if it was 15mm.
Why don't you fit a 22mm isolation valve on the cold instead and partially close it to restrict the cold supply? Er,like you said you were going to do?
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Because if the pipes had both been run in 22mm in the first place, ie correctly, there would have been a better flow available at the mixer than by installing a restrictive 22mm valve on the cold supply. If, as you say, the council show no concern (default mode?
) then I will fit the valve.Firstly i am going to assume the cold supply to the bathroom is from the mains.
If that is the case your pressure IS balanced.
You have a combi fitted so the hot supply is fed from the same cold mains supply therefore same pressure.
There is a greater flow rate from the cold because the volume of a 22mm pipe is over twice that of a 15mm pipe.
It would make not a jot of difference if the hot pipe to the bathroom was a 42mm pipe as the cold supply to the combi is 15mm. The flow rate through the combi is also restricted to around 2 gallons/minute dependant on the boiler make size etc.
Solution - fit a service valve to the cold.
If the cold supply to the bathroom is tank fed the supplies are unbalanced. Although the hot has a lower flow rate (governed by boiler) it will have a higher pressure.
Solution - Alter the cold to the bathroom to mains supply to balance the pressures or fit an electric shower.
There is too much risk of scalding to fit a bath shower mixer to this set up.
The council have no obligation to alter anything on this system but you have an obligation to tell them you are installing a shower!
If that is the case your pressure IS balanced.
You have a combi fitted so the hot supply is fed from the same cold mains supply therefore same pressure.
There is a greater flow rate from the cold because the volume of a 22mm pipe is over twice that of a 15mm pipe.
It would make not a jot of difference if the hot pipe to the bathroom was a 42mm pipe as the cold supply to the combi is 15mm. The flow rate through the combi is also restricted to around 2 gallons/minute dependant on the boiler make size etc.
Solution - fit a service valve to the cold.
If the cold supply to the bathroom is tank fed the supplies are unbalanced. Although the hot has a lower flow rate (governed by boiler) it will have a higher pressure.
Solution - Alter the cold to the bathroom to mains supply to balance the pressures or fit an electric shower.
There is too much risk of scalding to fit a bath shower mixer to this set up.
The council have no obligation to alter anything on this system but you have an obligation to tell them you are installing a shower!
Tamz, this makes a lot of sense. What I forgot to mention was that the mains supply to the flat and, hence, to the combi, is via a ¾ inch steel pipe. Prior to the connection to the combi there is a steel to copper adapter followed by a 22/15 reducer. Also the combi does not deliver anything like 2 gallons/minute, it is actually less than 1 gallon/min. The boiler is a Vaillant, not sure of the size, but it is about 11 years old.
Thanks for the help, anyway.
Thanks for the help, anyway.
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