I have a Powermax 155 which is around 6 or 7 years old - the house was built in 1999. The hot water flow is very poor and when it was serviced last year an attempt was made to descale it with chemicals. This was unsuccessful and the blender valve was removed. I now have very hot water but still little of it. British Gas have recommended a new boiler although a local engineer has told me on the phone that they can be repaired although he can't do it. Is a chemical descale the only answer or can the coil be replaced and if so does anybody know who can do it?