Hi Gail, I'm afraid I don't have an answer but I too am suffering from the same problem. I also have the added problem of the boiler locking out, even whilst the tap is running. So far we have had a new expansion vessel, pressure valve, and 2 new thermostatic controls. The engineer is coming again tomorrow so if he tells us something else is the cause I'll let you know. However if yours is fixed already please can you let me know how as our engineer seems stumped.
Thanks
Claire
Claire
March 2007