Pressure drop - combi-boiler system

[hcyeow]

We moved into a house with a combi-boiler system. When one shower, nobody else can turn on the tap (unless you want a HOT shock of your life). Is there any simple fix to this problem rather than a complete change of our hot-water system.

[BillyNoMates]

Fit an electric shower - i.e. totally separate from the boiler.

[Harley]

Sounds very odd. I assume you mean the shower water gets very hot as the boiler pushes more hot water to the person opening a tap.You can fit a thermostatic valve to the shower that will prevent scalding as it measures the hot water temperature, here is an example.

http://www.edirectory.co.uk/pf/static/880/mi/763/p165876 3.html

[Harley]

Link looks bad put this in Google search

3000 Pressure Equalising Shower Valve

[trendypaul]

Combi boilers are good but can be problematic with regards to demand for hot water.  An electric shower would solve the problem although new wiring would probably need to be put in which could be a bit expensive (plus the cost of the shower), however many plumbers recommend Electric showers so that you will still have hot water if your boiler breaksdown.  A thermostatic valve is probably your best bet as it would be a shame to not use the fact that you get nearly mains pressure water from your combi.  They work by not letting the water get above a certain temperature as it comes out of the shower.  They will work if there are problems with either hot or cold water.  It would be useful to know whether the problem is that the shower gets hot when a cold tap is opened or vice versa.