Hi, I'm in the middle of fitting a mixer shower driven by my new combi boiler. The hot water pipe goes from boiler as a 22mm pipe up about 6ft vertically, across my attic for about 20ft , and then reduced down to 15mm and down into the ensuite where the shower is located. The problem is that the hot water doesn't get very hot or that powerful? The hot water taps deliver very hot and powerful water elsewhere in the house. Any thoughts?
Low hot water pressure from combi boiler
- Thread starter mikeF00
- Start date
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Any chance of telling us the model of boiler? 
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Sorry forgot. The boiler is Worcester 28i junior
So 10 or 11 litres a minute from the boiler tops.
Have you measured the pressure and flow at the outlets.
Have you measured the pressure and flow at the outlets.
Sorry , iVe no idea how I do that. ? Find it a bit strange that a relatively new boiler would struggle to produce a half decent flow. Any ideas ?
Is it producing the designed flow at the designed temperature rise? Or are you just guessing?
You need to measure the flow rate and the temperature difference between hot and cold.
You need to measure the flow rate and the temperature difference between hot and cold.
Boilers produce a flow and temperature rise according to their power and design.
But what you consider "half decent" is something that is totally undocumented or even tested.
What I can say is that it would be best to reduce the pipe across the loft to 15 mm and properly insulate it.
Otherwise you will be shifting a larger volume of cold water from that pipe every time you use it. As well as losing a lot of heat if its not properly insulated.
Tony
Taps have flow restrictors fitted. The shower does not.
thanks for the replies. I've re routed with 15mm throughout the pipe run. It's better but not great. I will insulate with that circular foam stuff as well. Does this make a lot of difference?
I guess the boiler just isn't up to it. Just assumed it would be.
I guess the boiler just isn't up to it. Just assumed it would be.
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