You need to take the front cover off the boiler, down one side you will see a flattened tank about 50mm deep and filling the side of the casing,on the top there will be a small valve like on a car tyre usually with a black dust cap,so you are not testing the central heating pressure you must let the water out with the expansion relief valve [its at the bottom of boiler with a red top,just twist ]test pressure on tank valve it should be between 0.5 and1.0 bar if not use a foot pump and pump it up taking care to let water out as pressure increases when you are happy with it refill system again
toptrish, November 2013
