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No particular reason to suspect an Expansion Vessel (EV) fault. Just try cleaning the PRV (safety valve) so that it doesn't drip. Turning the red knob to rapidly open and close it a few times is sometimes sufficient to get it seating properly. When you've dealt with the PRV you can check the...

He did too! I just receved this email from rudeboy .... I don't think hi-spec liked me correcting him on the cavitation thread!

Sorry, I still don't understand what point your trying to make :? .

Is that supposed to mean something? :?

The Heat Is On , 1982, by Agnetha of Abba. Cold Weather Blues, 1964, by Muddy Waters.

Congratulations on your cut and paste job from Wikipedia, hi-spec. It is normal to give an acknowledgement when you copy things from another author. Unfortunately for you it says nothing to support your assertion that cavitation is to do with air. The voids or bubbles referred to are full of...

No, it's nothing to do with air. It's to do with vapourisation of the fluid being pumped (in this case water) at the pump impeller due to a low static pressure combining with further pressure drop due to high pipework resistance (e.g. from NRVs).

So the tape isn't applied parallel to the threads? Does that make sense?

Handel's Water music?

If you start away from the open end and work towards it then a clockwise direction (viewed from open end) would not line up with the threads! It would have to be wound on anti-clockwise for the strands of tape to bed well into the threads.

On reflection I suspect that's the right way, that is to say anti-clockwise looking at the open end of the thread. At least that's what the official suppliers' web sites all say. I must give it a try next time.

Air will only be sucked in if the pressure within the system is less than atmospheric pressure (0.0 bar). This tends to occur at high points in a system and/or towards the inlet to the pump but only if static pressure itself is very low. For example if system pressure is maintained at 1.0...

I suppose you realise that the root of the problem is that your pipes do not have room to expand due to being tight against joists, etc. This may be in just one location so it might be worth seeing if you can identify the area by how loud the noise is. It might then be worth pulling up the floor...

Have you considered an unvented cylinder? You would then not need a cold storage tank or any pumps for the showers, but you would need a good mains supply.

Looks like your boiler has a bi-thermic heat exchanger, meaning the DHW function is combined with the main heat exchanger. That makes it a whole lot more complicated to change, especially since it takes you into Corgi territory. I guess the heat exchanger itself is going to be around £150 and...

Opinion seems divided. Here's a site where they say from the pipe end.

This is all explained in the FAQs. There are only two explanations for rising pressures. 1 - the expansion vessel has failed or lost its charge, in which case pressure would rise on heating and fall on cooling, or 2 - there is a leak from mains side to heating side, in which case pressure rise...

1.5 bar is much too high a precharge pressure unless the system pressure needs to be unusually high. At 1.5 bar precharge and system pressure of 1.5 bar, the EV would still be full of air since the water would push in only when the system pressure exceeds the precharge. Then if the system...

They're not called CET boilers, but if you Google on CET you get all sorts of other stuff. Sticking the word boilers in the search brings up CET directly. Probably work the same with fans or PCBs.

No, but it was in the days of Radiation - Ascot when they were part of TI (Tube Investments).