I have a pressurised hot water system with an unvented Hot Water Storage Cylinder (I think it is a steel cylinder). In the last few months there has been a constant brown tint in the hot water system - but none in the cold system. The system is 5 years old. The more I think about it the more I think it is the Cylinder which is rusting. It is an Ariston model... any ideas ?

Robert...

What you are seeing is iron oxide (rust) build up in the tank. This will happen if you don't flush out your yank on a regular schedule. Let me show you how.

For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear.
Good luck, Tom