Have had to replace the pressure relief valve - unfortunately, the way the boiler was installed (pipes not far enough back away from the heat exchanger) I had to remove the return unit to be able to access the valve. This is where things went a little awry... the by-pass valve (87161064340) fell out from the return unit . I have looked at the hydraulics diagram which looks as though the black cap end goes into the unit first, but obviously need to get it correct and there is no 'flow' arrow to indicate which way the valve should be positioned; any help gratefully received.
Thank you
Thank you