The French Gulch Water tank was used I believe on a fairly regular basis by standard gauge trains, which direction it was used I do not know. Now there was a tank between Leadville and French Gulch, the Three Mile tank located at milepost 147.6 which was demolished on November 20th, 1945, and was never used during the standard gauge era.
I would also like to argue that the French Gulch tank is the original tank used on the narrow gauge. From High Line to Leadville by Doris B. Osterwald which is the official guidebook of the LC&S, "The 47,500 gallon wooden tank has had an interesting history. The tank originally stood on the opposite side of the track, but in 1943 when the High Line was converted to standard gauge, it was moved and raised so the spout would fit over the taller standard gauge engine tenders." The picture linked above I believe is of workers preparing to move the tank to its new foundation. The LC&S book has a picture of C&S #76 taking on water at French Gulch on the final day of ng operations, August 25th, 1943, with crews preparing to move the tank. Also, C&S High Line Memories and Then Some by Tom Klinger, "After the High Line was changed to standard gauge, the French Gulch Tank was moved to the west side of the tracks..."(224).
The relocation of tracks is due to a washout on June 23rd, 1980 of the fill over French Gulch which caused a Burlington Northern locomotive #6223 and a tank car to go over the edge. Repairs to the fill cost $50,000 and when the the fill was rebuilt, the track were replaced on a different alignment.
This discussion from 2009 has a little info to.
http://ngdiscussion.net/phorum/read.php?1,131788,131788#msg-131788
Alex