I have a Telford Tornado 85 copper water tank which is about 15 yrs old. occasionally we get water dripping from the ' TUNDISH'. I have been told that the bag in the tank may need replenishing, this has been done about 4 years ago by a plumber but he said I could probably do it myself.I have emailed Telford requesting a user manual on how to do this and have even been on their website looking for instructions but had no luck. Has anybody got any ideas or can tell me where I might find the instructions. Thanks in advance.