I am in the process of fitting a WC and small corner basin in what was an unused alcove upstairs in our house. I intend to use a small instantaneous water heater over the sink for hot and cold water. The electrics are being sorted by someone with the appropriate qualifications so no problem there, but he pointed out that according to the installation instructions, it is preferable for the mains cold water supply pipework to the heater unit to have nothing else on it or else it could cause a pressure drop and stop the heater working properly.
For example, at the moment, if someone uses the WC and then washes their hands, I assume the water pressure to the basin could be affected by the WC cistern refilling or will the fact that it is mains supply keep the pressure correct in both places?
To avoid this problem, could I use two separate feeds from the rising main in the loft i.e. one to the WC and one to the water heater?
Any advice welcome!