just for those who are wondering:

the change is the recipe for the underground pipes now use 2 and produce 2 for each crafting.
Before was 1

@kendfrey: why dont u use the high pressure pipe as an ingedient, like other pipe-recipes do?
(using pipe of the same tier to craft underground pipes)

The base pipe-to-ground recipes include raw materials and pipes. There is no raw material for high-pressure pipes, so it made more sense to just make it a direct multiplier of the base pipe.

you are right...

but it confused me in the beginning, since i expected to lose HP-pipes, when i crafted HP pipetoground - just cause i was used to this mechanic...