Potter 1010117  WLS Tank Water Level Switch is a float operated device for supervising water level in a sprinkler supply gravity or pressure tank. The Model has a bushing with 1 1/2 Inch American Standard Pipe Threads for mounting in steel tanks. A 1 1/2 Inch x 2 Inch adapter bushing is available for mounting in existing 2 Inch steel flanges. An optional bushing adapter with a buttress thread is available for mounting in wooden tanks. The unit is capable of detecting the level of water before a 3 Inch (7,6cm) rise and/or a 3 Inch (7,6cm) fall in the water level in a pressure tank, as required. The cover is held in place with two tamper resistant screws (provided), which require a special key for removal.