Fittings Measurements Different Then Expected ( 1/4 and 3/8 fittings )
Customers confused by the "Size" of 1/4" fittings because they "Look" to be 3/8" in width.
** This is because the 1/4" female opening is 3/8" across if measured.
And the 3/8" female opening would be about 7/16" or nearly 1/2" across if measured.
Also, see,
1/4 f x 3/8 c,
3/8 f x 3/8 c,
1 ) The Elbow that connects to the Air check threads is the most common to "confuse".
NOTE: Be sure to use Teflon Tape or similar product ( like our Lock Leak ) on the male Threads of the Air Check ( where the female fitting must thread on to ).
It is NECESSARY, or it will develop an "air" leak.
For older 36F Air Check ( used on most 155 models ), it would be this male x compression fitting, 1/4 male x 3/8 compression
And for newer style air check ( used on all 255 models and late model 155 and all Technetic 1000 valves ), the fitting is 1/4" female x 3/8" compression nut
( since most systems use 3/8" O.D. brine tubing ). 2 ) The Elbow that connects to the Brine Pick Up tube in the salt tank area have Two compression nuts that should be checked to make sure they are tight.
And the fact there are 2 nuts be checked is often over looked.
** A partial leak in either of these Elbow connections may allow some water to be removed from the brine tank, but the ball "drops" in less then 60 seconds, due to air getting sucked in at the same time.
3 ) The tubing between the air check and the brine pick up tube can become cracked or if have a pin hole in it that allows air to be sucked into the Valve ( into the Air Check chamber ) and the ball drops before any of the water from the salt tank gets removed ( drawn out ).
For other reasons that a Brine Tank may be overflowing, or the salt water not being sucked out during the Brine Rinse cycle,
See: # 1 FAQ = High Water in Brine Tank - Problem
The older 36F ( on left ) is an OBSOLETE PART > Air Check Assembly used on Autotrol 155 prior to 1993.
Assembly threads on to Tank Adapter.
Old PN # 36F - No longer made, nor available from any source.
NOTE: Replacement options explained on product page. Old PN # 36F
Air Check - New Style ( kit 1032417 = Air Check Kit, 1/4" Male )used from about 1993 to present.
Can NOT be used in place of the old style ( see part # AP36F ).
Used only on late model Autotrol 155 and all 255 water softener valves.