This is the the underside of a water heater fitted to a warm air unit. The customer informed me that he has the unit serviced every year, but this year the chap was off sick and was unable to attend so he phoned CORGI and asked for a list of registered installers in Baldock. The customer was surprised not to see the person who had serviced this unit for the last few years, the reason he was not registered and by all accounts  he did not have a clue what should be done when servicing water heaters.

A new water heater was fitted and the warm air unit fully serviced.