"Paul Bendall" wrote in message
...
Hi All,

As of last weekend the water system has been playing up, only the hot
water
system is currently running the central heating is turned off. When the
boiler is turned on and the pump activated the boiler fires up, after a
few
seconds a noise is heard from the pipes feeding the boiler up to the
expansion tank for the central heating. This is the smaller tank in the
roof, this then overflows with water. The boiler then shutsdown for about
30
seconds and then the whole process starts again.

The boiler had not been working as the pilot light would not stay lit,
this
was rectified by a Corgi plumber and everything was okay for a few days.
Then the above troubles materialised. It was suggested that I turned on
the
central heating and tried to bleed air from the radiators, I have tried
doing this and released about 15 buckets of water from the system, but it
is
not getting any better.

Anyway got any ideas or suggestions?

(1) Are you sure the pump is running? If the pump is not running, the boiler
could be literally boiling, then the steam pushing water out of the
expansion pipe.

(2) If you run the central heating do the radiators get hot? If not this
again suggests that the pump is not working. This can be due to a faulty
pump, or due to an air lock near the pump or air in the pump. Have you bled
the pump?

(3) As suggested by BigWallop, if your valves are closed then again water
will not circulate even though your pump is running and the symptoms as
described could occur.

Some things not clear from your post:

(1) Is the hot water heating up O.K.? If so, is the hot water side pumped or
via gravity?

(2) If both CH and hot water are pumped do you have two seperate valves, one
for hot water and one for CH, or a single threeway valve?

(3) Does this problem happen when running HW only, CH only, or both together
(or all three)?

Cheers
Dave R