Worcester bosch combi boiler pipes knocking, pressure drop..

Hi

We had the diverter valve replaced on our boiler last year, but now again the hot water wont work unless the central heating is on.

Two other problems!!

1- The pipes knock when the CH comes on in the morning and at night. Its not extremely loud, just annoying and wakes my son around 6am!! (Believe water may be too hot or pipes loose...will check if that sounds right?)

2- The pressure drops gradually by approx 0.1 bar every week or two. So every month or so I top the water back up to 1-1.5 from about 0.5 (Cant see any leaks anywhere)

Help!!
Any advice??

The pipes knocking will most likely be the noise they make when they expand against adjacent joists/floorboards if they are tight up against them. You can get the boards up and put some hairfelt lagging between them to stop it.It's not affecting the operation of your heating though.

The pressure loss could be a minor leak you can't see which evaporates with the heat or it could be the expansion vessel playing up- there are lots of threads on here which explain this-it either needs re-pressurising or a new pressure vessel could be needed.
Again you could carry on for some time with how it is at present-it's not a fault with the boiler as such.

The automatic air valve or AAV is a common leaky culprit on these - the part costs less than a tenner.
John

Hi
Diverter valves go regulaly if it was not a genuine worcester part as there is alot of cheaper universals out there,
I agree the knocking is expansion on joists, try lagging pipes on joists
Has the pressure dropped b4 or only after the diverter valve was swapped if it wasnt check the copper pipe outside to see it is dripping,
most plumbers drain the system by using the pressure relief valve and when refilling it dosent reseat causing it to drip, a new pressure relief valve will be needed
hope this helps

Thanks for all responses.

Pressure drop only started after diverter valve replaced...the lad was a bit of a cowboy to be honest so wouldnt be surprised if he didnt do everything properly!

I will get the boards up and check where the noise is coming from

Will also get a reputable plumber in to look at the AAV!

Thanks again