i am currently working towards my ACS and was wondering about a problem my mother has had with her water heater for many years. When she runs the hot tap the heater lights up and heats the water fine, but if she then turns on the cold tap or flushes the toilet the water from the hot tap stops being heated and eventually runs cold (at the same time the flame reduces in size in the water heater). i was wondering if this could be something to do with the cold water flow rate being reduced into the water heater or could it be incorrect pipe sizing. i have had a look at the pipe sizing and i think it is too small for the amount of appliances it feeds. i have not done all the calculations yet but initial thoughts are they are too small.
any suggestions would be a great help