"Tim Watts" wrote in message
...
Does this actually mean what I think it means - the distance between the
vertical centres of the pipes as they come up from the floor into the
valves?

Because it seems an odd measurement and assumes all 90degree rad valves
have the same joint offset dimensions.

Or does it mean "distance between the two shoulders of the threaded ports
in the rad"?

It matters in a couple of cases

The pipe centres can only be a nominal dimension.
Waste of time really as they don't know which valves will be fitted.

The table has not been compiled by a technical person, there are other
errors in it.