New answers tagged ice-maker
Based on size, location above the baseboard and distance from the wall and the fact that it is a screw-on cap, I'd guess gas.
Try to scrape/sand away the paint to see what material you find. As mentioned in @Pigrew's answer it could be black iron steel, galvanized steel, or brass. However, it's hard to tell by the photo if it is a threaded cap or not. If it's not threaded it could be copper, which is used for both water and gas. And for the sake of completeness, it could also be ...
Short of opening up the end-cap, there isn't a good way to tell which it is. You could try banging/hitting a pipe elsewhere in the house, to see if you can hear the banging. Also, look at other exposed piping to see what materials were used for the various utilities. Pipe like that could be water, but it also could be oil or natural gas. There is a chance ...
Top 50 recent answers are included