No.1 U.K. Professional Trade Forum, Plumbing, Gas, Electric, Tiling and Joinery Forum

Hi all,
I've got a question regarding water pressure before i fit a new combi boiler. I'm hoping you can help.
I'm looking to fit a boiler on the first floor of my house (outside the bathroom), with the flue vented through the roof. This, for me, is the best position in the house.
The problem that i have got is that the water pressure upstairs halves when the kitchen tap is turned on. The main stoptap is next to the kitchen sink.
I measured the water pressure and got the following readings:
Only kitchen sink tap on: 11-12ltr flow rate/ just over 2 bar.
Only upstairs bathroom on: 10ltr flow rate/ just under 2 bar.
With the kitchen sink tap on full:
Upstairs bathroom drops to 4ltr/ 1 bar.
Would i be able to fit a combi boiler or am i better opting for a system boiler and tank?
Your help would be much appreciated.
Thanks,
S.

Hello,
Your measurements taken from taps will be influenced by what flow rate the taps themselves have and how they are piped - pipe sizing and if any restrictive isolating valves or flexi hoses are fitted.
Your kitchen tap could be controlled for flow rate by a more restrictive aerator in spout or flow reducers in pipework to help prevent robbing flow to bathroom.

Looks like your flow rates are still poor though and a system boiler staying with a hot cylinder and cold water tank might be best. Shower pump then an option.
Have you asked a gas installer to check it all out and give you advice?

Hi Best,
Thanks for the quick reply. I've contacted a gas installer regarding a visit so i will be getting further advice, but wanted to do a bit of research to understand the issues. Would i need both hot and cold water tanks? I have both at present but was looking to remove the cold tank and put in a larger hot water tank. (I was looking to get rid of both to be honest by installing a combi, but the water pressure issue has made me think twice.)

To keep a hot water cylinder and have no cold tank would mean having an unvented hot water cylinder.
You still would have the problem of pressure and flow rates needing to be adequate.
Usually would want 20 litre flow and 2 bar pressure or higher