ive got them from Plumb Center in the past.
these things.
http://www.plumbingsupplyservices.co.uk/acatalog/Chrome_Plated_Radiator_Extensions.html#aCPEX20
http://www.diynot.com/forums/viewtopic.php?p=251090#251090
don't worry if a little water comes out of the schrader valve as it is located at the bottom of the expansion vessel & may just be due to condensation.
i agree.
but i am talking pretty much infallible.
nothing else i can think of can compare.
i recall going on the vaillant course when the second generation turbomax came out & they said the new diverter was bullet proof.
bo**ocx.
what on earth has it got to do with the dog.
i detest using the gas stuff on anything.
ordinary ptfe is made for the water job.
gas jc is the only stuff for small bore gas.
gas ptfe is ok for making up grommets, o rings, stuffing glands etc.
you said you get hw.
so the pin on the water section must travel out when the hot tap is opened in order to move the cam to operate the microswitch.
diverter microswitches
boiler off- top micro out. bottom micro made.
hw on- both micros out.
ch on- both micros made.
the servo...
i dont think you know what your talking about.
ov & cf appear to tee in just before the pump.
granted the valves may need turning around & no bypass evident.
other than that no major visible fault.
i would check if the expansion vessel is sufficiently charged re the pressure rising.
regarding your ch problem. its worth you taking a look at another active thread as it applies to you too.
http://www.diynot.com/forums/viewtopic.php?t=151738
the middle picture is right for dhw...
see all those tiny little tubes. there is probably some muck stuck in them.
they should be checked/cleaned. also so should the servo valve (black & white plastic bit with four tubes entering it) & the pressure differential valve (black plastic bit with two tubes entering it) while you're at it...