1/2-3/4BPRED – GAS PIPE (3/4-1/2″ BUSHING)

Smith Cooper Class 150 black malleable iron hex bushing that reduces 3/4 in. male NPT to 1/2 in. female NPT. Used to step a 3/4 in. black iron gas line down to a 1/2 in. connection at a valve, drip leg or appliance inlet. Outside-hex pattern, made to ASME B16.3 dimensions from ASTM A197 malleable iron with ASME B1.20.1 threads.

Specifications published by the manufacturer. Source: manufacturer documentation.

Specs

• FigureFig. 33HB1, Hex Bushing
• Size3/4 in. x 1/2 in.
• End ConnectionsMale NPT x Female NPT
• Hex TypeOutside hex (Type A)
• Pressure ClassClass 150 / PN 20 per ASME B16.3
• MaterialBlack malleable iron, ASTM A197
• Dimensional StandardASME B16.3
• Thread StandardASME B1.20.1
• FinishBlack

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• R54-491
• 0810086009

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

How do I size black iron for a furnace?

By BTU load and developed length, using the longest run in the house. Schedule 40 at 0.60 specific gravity and a 0.5 inch water column drop carries about 119 CFH in 1/2 inch at 20 feet, 249 CFH in 3/4 inch and 469 CFH in 1 inch. At 60 feet those fall to roughly 66, 137 and 259. Natural gas runs about 1,000 BTU per cubic foot, so 3/4 inch at 60 feet developed length is good for around 137,000 BTU. Developed length means measured length plus the equivalent length of every elbow, tee and valve, and if you land between two columns you take the longer one.

Which sealant goes on the threads?

One rated for fuel gas. The code language is that the joint compound has to be resistant to the action of the gas, which rules out the thin white plumbing tape. Use gas-rated pipe dope or yellow gas-rated PTFE tape, male thread only, started a thread or two back so nothing squeezes inside and lands in a gas valve.

How do I leak test?

Pressure test first, then soap. The fuel gas code calls for 1-1/2 times working pressure and never less than 3 psig, held at least 10 minutes, and plenty of DFW cities want longer - ask your inspector before you pump it up. Once it holds, brush soap solution on every joint and watch. A lighter is not a leak detector.

Is CSST the same as black iron?

No, the rules are different. CSST uses only its own manufacturer's fittings, has its own sizing tables, and requires bonding to the grounding electrode system per the manufacturer's instructions. Never mix fitting brands and never treat a CSST run like rigid pipe.