I have an annoying problem with my GHW system.

When the boiler first fires it appears that the water is heated then it
boils for a short time (maybe 30 sec max) before it starts to naturally
circulate.

If I turn the water off, then the boiler shuts down as it should.

If I then turn the water on again, the boiler then re starts and the
water is heated without the boiling noises.

Any Ideas how I can get the water circulating before the boiler fires
as I think this would cure the problem.

I'm going to see if it is possible to start the pumped CH for a couple
of minutes before the GHW starts to see if this does the trick.

I've already descaled the system, flushed and treated with Fernox noise
reducer and protector (maybe I should add more?).

Any Ideas gladly considered although I don't really want to change to
pumped HW

Kev