AirComParts In-Tank Check Valve, 3/8 in. to 1-1/2 in., NPT and Compression
The in-tank check valve threads into the tank bung and holds the receiver's pressure back while the pump is stopped. It also carries the side port that bleeds the discharge tube so the compressor restarts unloaded. When it fails you hear it: air hissing back out of the unloader after shutdown, a pump that will not restart under load, or a motor that trips its overload on every start.
Sizes
- 3/8 in. NPT x 3/8 in. Compression (S1141)
- 1/2 in. NPT x 3/8 in. Compression (S1615)
- 1/2 in. NPT x 1/2 in. Compression (S1142)
- 1/2 in. NPT x 1/2 in. NPT (S1050)
- 3/4 in. NPT x 3/4 in. Compression (S1035)
- 1 in. NPT x 3/4 in. NPT (S1078)
- 1 in. NPT x 1 in. NPT (S1140)
- 1-1/4 in. NPT x 1-1/4 in. NPT (S1029)
- 1-1/2 in. NPT x 3/4 in. NPT (S1022), which fits Kellogg
Reading the two sizes
The first figure is the tank thread. The second is the discharge connection, and that is where people order the wrong part. A compression fitting takes copper tube straight into a ferrule and nut. An NPT outlet takes a threaded fitting or a flex line. They are not interchangeable, so check which one is on your machine before ordering rather than after.
Fitting notes
Bleed the tank to zero before you touch anything. Thread sealant on the tank side, not on the compression side, because a compression joint seals on the ferrule and sealant there just makes a mess. Do not overtighten the compression nut on soft copper. If the unloader line is brittle or kinked, replace it while the valve is out, since a blocked unloader line produces exactly the same hard-start symptom as a bad check valve and you do not want to do this job twice.
Brass in-tank check valves for reciprocating air compressors, sized 3/8 in. through 1-1/2 in. in both NPT and compression outlets, with the unloader port that lets the pump start against no load.
NOTE: Actual product may be different from pictured!
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