Black Iron Nipples

Black steel pipe nipples, threaded both ends, for gas, steam, compressed air and hydronic. Sizes 1/8" through 4", in lengths from close through 12" and longer.

A close nipple is threaded end to end with no unthreaded shoulder between, so it is the shortest possible connection between two fittings. It is also the weakest and cannot be gripped with a pipe wrench without damaging the threads — use an internal nipple wrench, and where the run allows it, choose a short nipple with a shoulder instead.

Black steel is the default over galvanized on interior fuel gas piping, because zinc flakes shed into the line and foul controls downstream. NFPA 54 permits galvanized steel pipe for gas, so this is a local code and utility requirement rather than a national prohibition. The two look nearly identical once installed, so check before ordering.

Threads are NPT taper. Cut ends should be reamed; the burr left by cutting restricts flow and, on gas, can catch debris.

Predominantly Mueller Streamline, with Pasco.

Nipples are made to ASTM A733, a different standard from the malleable fittings around them. Length tolerances, thread engagement and pressure ratings are in our black iron reference guide.