On 06/04/2019 23:05, Java Jive wrote:

[...]

I've seen, for example ...

Level:
Â*Â*Â*Â*https://www.amazon.co.uk/Distance-BE...f=sr_1_17_sspa

X-beam:
Â*Â*Â*Â*https://www.amazon.co.uk/Vorstek-Adv...f=sr_1_49_sspa

I can now report back that finally I went for ...

X-Beam Level (as above):
https://www.amazon.co.uk/dp/B07DLX4SDT

Listed as Vorstek as above, but badged Hanmer LV2. So far, limited use
but excellent, particularly for the price.

Measure (finally chose model with better ratings than above):
https://www.amazon.co.uk/dp/B076Z937LY

So far, even more limited use, but given the doubts about the accuracy
of these things, I've specifically checked that over a room width of
about 3m, and it's accurate to less than 1mm over that distance, as far
as I could judge, probably to around 0.25mm.

The cross-beam level has been an almost miraculous help getting the fall
right on the tundish outfall in my bathroom, which has to go 2m within
the partition wall from the corner where the new tank will go along the
length of the bath and then a further 700mm through an old stone wall,
and over that distance it has to be accurate to within about 1cm,
because it has to be below the attachment points on the tank, have the
correct fall, yet has to exit at a minimum height within the room to
come out above a lean-to roof outside. The wall section part is proving
*very* difficult, because of the hardness of the stone, and on & off
I've been working at it in bouts for days, but I'm very nearly there now.