Yes, we can help you. We can sugest how you could think this rrough to answer the question yourself.
How long is the pipe between the boiler and the tap is full of water, which has to be run off each time you use the tap. If the tap has not been run for a while, that water will be cold, won't it?
So. How long is that pipe?
You can work out how much water that involves (inside diameter [in cm] square, times 3.14, divided by 4, times length in cm. Divide by 1,000 to get the answer in litres.
If the pipe is bigger than 15mm OD - say 22mm - there will be even more water to run off.
XXX, June 2016
