We have very little space upstairs, so unless the pressure/flow rate is completely disastrous, I think we're really after a combi boiler. From what I can see I think we have very good water pressure. The taps in the kitchen seem to blast water out of the sink if turned on too much.
Is there an easy way to check pressure and flow?
It sounds as if you are in a small house, possibly only two bedrooms with just a bathroom and a kitchen, so having two showers going at the same time is not a possibility. If that's the case, a combi will probably be OK. But do bear in mind that
all water, hot and cold is supplied from a single source, the incoming cold water main. So flushing the toilet while someone is having a shower is not a good idea. The same goes for running the washing machine or washing the car with a hose (if that's permitted
).
As for checking flow and pressure. The simple way is to use a bucket and a watch with a second hand. Time how long it takes to fill say 10 litres and then convert this to litres per minute. Pressure really needs a pressure gauge, but you can get a good idea if it is adequate if you have a garden tap connected straight to the mains. Do the sink test with the garden tap closed, then with it fully open. Provided there is not a considerable difference in the flow rates, you shouldn't have any problem.
The sizing of a combi (kW) for hot water depends on the flow rate; you need 2.5kW for every litre per minute flow. If you have a larger boiler all you will get is hotter water.
The central heating output also need to be taken into consideration as most combi boilers produce much more than the typical house requires. Use the
Whole House Boiler Size Calculator to find out your heating requirement. Then compare it with the CH output of the boiler(s) you are thinking of buying.
Ideally the required CH output should be below the max boiler output and well above the minimum output.