We have a 2.0 pump on the hot water supply at the top of the house because of low water pressure. What is the implication of switching to a combi boiler?

By switching to a combi boiler, you will in effect remove the Hot Water Cylinder and Pump and replace your existing heating boiler if you have one. Your hot water would then be supplied by the combi boiler at the same pressure as your cold water. This is known as mains pressure hot water. The combi boiler will also do the central heating, hence the prefix 'combination' .

If you have poor Mains Cold supply to the property then this will not change with a COMBI Boiler, except that you cannot run pumps with the system and thus all taps, etc. will have low pressure. If you have good Mains Supply pressure to the property then you should get decent pressure to all Taps, Etc. where ever they are in the property. But to get the best out of the pressure, you will need to have a CMBI Boiler that has a good flow rate of about 15 Litres per minute, most COMBI Boilers run at a lot less than this. Also, with a COMBI Boiler if you are running Hot Water and someone elses turns a Cold tap on or flushes the toilet this will take away water and you will probably find a sudden increase in temperature and drop in flow. If someone turns on another Hot Water Tap then you will find that the flow will reduce. This is why you need to have a Boiler with good Flow Rate. The minimum water pressure of the mains should be 1 Bar before thinking about installing a COMBI Boiler, but in reality you need in excess of 1.5 Bar pressure. Bill Pipe Dreams Plumbing Services Bournemouth