On 18 May 2021 at 12:01:08 BST, "D.M. Procida" D.M. Procida wrote:

What's a typical cause when a boiler starts to require increasingly high
demands for hot water before it decides that it should light up the
burner to deliver it?

My guess is that there's a pressure drop valve, and that it has become
stiff or its seals have become sticky.

Daniele

In my (limited) experience it is usually a flow valve. Which is easy to
replace if you can get at it at all.

--
Roger Hayter