No water upstairs

[johnf89]

Hi
I have builders in my house doing various works, but at the moment my main concern is my water. When I have the taps on in my bathroom hand basin or bath and the kitchen taps downstairs are turned on, I lose all water upstairs. I have a new combi boiler fitted and my old one never used to do this. I did have a water tank in the loft in use before, which they have now disconnected. I wouldn't have thought this would be the problem though, would it? The plumber I asked said typically, " I have a combi boiler mate and it does the same in my house" Any suggestions would be welcome please. I am having an electric shower being fitted in the next couple of days and it's not going to be nice if this happens when I'm in the shower.
Thank you in advance for your help.

[plumbbob]

You shouldn't lose water flow upstairs when downstairs taps are turned on. This suggests a problem with the main incoming supply. Adequate pressure should have been checked before the combi was installed so was this done?

Your plumbers reply isn't very helpful. Just because he has got a problem doesn't mean you should too.

How does the pressure at the kitchen sink cold tap compare now against how it was before the work started?

[johnf89]

There doesn't seem to be a lot of difference. All the taps have good power when just one is turned on alone.
They lose power as another one is turned on and so on. Turn the cold on alone, good power. Turn the hot one on and the power is halved. This happens upstairs and downstairs. I honestly don't think the plumber really has a problem in his house. He was just trying to fob me off by telling me that this situation is normal, hoping I would fall for it.

[Barry Bunsen]

It is probably the water flow that is concerning you rather than water pressure, although the 2 are linked.
You should still get water flow upstairs when a downstairs tap is turned on with a combi but the flow will be reduced. Electric showers can go cold when the washing machine kicks in for example.
Your boiler handbook should give information on what flow rate is required in litres per minute for the system to work properly. As a rough guide you can measure the flow rate from a tap using a measuring jug and stopwatch
You can also measure the water flow from a couple of taps individually and then with both turned on together. The results should compare similarly with those of a friendly neighbour with a combi, as the water pressure to each house should be about the same (as long as all the taps are sound).
If the neighbours combi functions better than yours I'd be asking why but remember it may not be the plumbers fault.