In article ,
Stephen wrote:
Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!

He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

Which was caused by an immersion heater - not boiler. You'd need a number
of faults before a boiler could produce boiling water. And even then, a
properly designed open system should cope without the above sort of
incident.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

First - are you talking about open vent primary or secondary?

I've just DIY replaced my gas boiler and changed the primary to
pressurized, but kept the secondary (hot water) open vented.

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*Someday, we'll look back on this, laugh nervously and change the subject

Dave Plowman London SW
To e-mail, change noise into sound.