A Trade Secret

Ailz, who has been keeping score, says this is now the third time our boiler has conked out since it was installed just over two years ago.  The first of the two engineers who came to look at it (he was young and uncalloused) let me into a secret. He said the maker's instructions stipulate that the entire heating system should be cleaned out with chemicals before a new boiler is installed- but it's a  pokey, time consuming job and most firms don't bother. As a result the boilers get gunked up with debris- and fail- which is what has almost certainly happened with ours.