Brass Fittings

Machined brass earns its place by a combination no other inexpensive material offers. The copper-zinc alloy cuts fast and cleanly, so complex bodies come off the machine cheaply and with sharp threads; it does not rust the way carbon steel does in wet service; and it will not spark if a wrench slips.

That puts brass where pressures are modest and the medium is not the problem: potable water, compressed air, instrumentation, and low-pressure fuel and lubrication. It is the default in shop air and plumbing for the same reason it is rare in high-pressure hydraulics — what makes it easy to machine makes it much weaker than steel. Potable-water service in the US calls for a low-lead alloy, so the alloy matters as much as the shape.

Where it's specified

• Compressed air and pneumatics — barbed and threaded bodies handle shop air and resist the moisture that condenses in the line
• Potable water — low-lead alloys are the accepted choice for drinking water and take threaded or compression ends
• Instrumentation and gauge ports — small precise bodies at low cost, with clean threads that seat gauges without galling
• Fuel and lubrication transfer — low-pressure lines where a non-sparking, corrosion-tolerant material is worth more than raw strength

Range and materials. Hose barbs, adapters, unions, elbows, tees, crosses, plugs, caps and compression bodies, machined and forged, with nickel plating where appearance or extra corrosion resistance is wanted. Ends cover NPT, BSPP, SAE straight thread, flare and compression in the small and mid sizes.

Ordering notes. Brass threads are soft and will strip or gall if torqued like steel, so pull up to seal and stop; on tapered threads use tape or paste sparingly, off the first thread. Never carry across the steel pressure rating of an identical shape, and keep brass away from ammonia and ammonia-based cleaners, which cause stress cracking. Where water is hot, soft or high in chloride, specify a dezincification-resistant alloy.