Things are a little confused here. Scoble, my primary reference for dates, says the station was first opened in 1903 and known as Trevor's Siding, but Parsons says the station was known as Welch's Siding back in 1897. In this case I trust Parsons more as Scoble has a few other omissions on this line - I suspect her source is... suspect. Whichever it was, it was renamed as Pitcaithly's Siding in July 1905. Perhaps a business ownership change? In 1924 Railways opened it for general passenger traffic, and in 1938 closed this Pitcaithly's Siding and moved the shelter shed 600m south for use at Andrews station. (Notice that Pitcaithly's has an apostrophe but Andrews doesn't. Go figure). Heck, even the move south is confused with some references saying 1.2 km and others saying over 3km. But I am pretty sure it was here, as I have other sources that some seem to have missed - Railways own timetables, which mention the distance to each station to within 20m.
The siding was originally installed to service a local industry. My guess is that Welch's was a sawmill as that is usually the first thing to go in. Either that or a quarry, probably quarrying the river. None of my references say anything about what industries some of these little sidings served. However I bet that goods services stopped here when freight services were withdrawn from other stations along this line, in August of 1876, despite the Trevor's opening in 1903. Yes, I am confused. This station would then have become passenger only, yet the station name was still listed as Pitcaithly's Siding in 1911, even though there was no actual siding then. Which makes me wonder if there ever was one!
So not a lot of information here. And very confused. Sorry. The station site itself has now been ploughed over by a highway, and most evidence that it was once here is long gone. All that is left is an old path leading to a bus stop on the highway, that was probably used for the station. You can see this where the sealed loop here joins to its road.
Pitcaithly's shelter shed in its new home at Andrews.
References:
maps.nzrailmaps.nz
"Railway Directory", Hutt Valley Independent, 2 September 1911
Scoble, J: "Names and Opening and Closing Dates of Railway Stations", published by the Rail Heritage Trust of New Zealand, 2010.
Parsons, D: "Wellington's Railways Colonial Steam to Matangi", published by the New Zealand Railway & Locomotive Society, 2010