On 31/08/2016 21:02, John Rumm wrote:
Does the bubble have to be absolutely dead centre or am I trying to
hard. What are the accepted tolerances?

I think sometimes we are too clinical. I remodelled a shower room a few
months back and came on here for advice as the walls were all over the
place, it was driving me insane. The advice given was `if it looks right
then it is ok` so I followed advice and although if I use a spirit some
walls are out of plumb it actually looks ok.

Its a balancing act if some of your walls were out of plumb before and
you never noticed then dont fret about it. I take the view nowadays
that I made an improvement, it may not be perfect but it is better than
what it was.