Editing Guide to mapping (section)

=== Pipes and manifolds ===

Atmospherics releases it's cocktail of gases into the air supply loop (blue pipes). The station is also equipped with a scrubber loop, which filters unwanted gases and sends them back to atmospherics via the scrubber loop (red pipes).

If you're expanding the air supply loop (blue pipes) use the objects in /obj/machinery/atmospherics/pipe/simple/supply/visible or ../hidden depending on if you want it to show above floors or below them. For manifolds use the objects in /obj/machinery/atmospherics/pipe/manifold/supply/visible and ../hidden.

If you are expanding the scrubber loop (red pipes) use the objects in /obj/machinery/atmospherics/pipe/simple/scrubbers/visible or ../hidden depending on if you want it to show above floors or below them. For manifolds use the objects in /obj/machinery/atmospherics/pipe/manifold/scrubbers/visible and ../hidden.

If you are however building a pipe network which has nothing to do with the air supply or scrubbers loop, you should use the objects in /obj/machinery/atmospherics/pipe/simple/general/visible or ../hidden. For manifolds use the objects in /obj/machinery/atmospherics/pipe/manifold/general/visible and ../hidden. 

To add new colors of pipes, you will need add a new subtypes in the appropriate .dm files located in tgstation\code\modules\atmospherics\machinery\pipes

Please refrain from var-editing pipes, as it typically introduces graphical glitches and other issues.