Stainless Steel Fittings

Threaded stainless steel pipe fittings from Legend Valve in 304 and 316, 1/2" through 2-1/2": couplings, reducing couplings, hex bushings, unions, tees, 45 and 90 degree elbows, street elbows and caps. All NPT threaded — there are no welded, tube-compression or sanitary tri-clamp fittings in this collection.

404 is 304, 416 is 316. Across this line the part number prefix carries the alloy: 404-xxx parts are 304 stainless and 416-xxx parts are 316. Two fittings of the same size and shape sitting next to each other on the shelf are told apart by that prefix, not by appearance.

Choosing between them is a chloride question. Both alloys handle ordinary corrosion. 316 adds molybdenum, and what that buys is resistance to chlorides: salt air, pool and spa water, de-icing runoff, brine and many process chemicals. Inland potable water and general mechanical work is 304 territory. Coastal, marine and chlorinated service is where 316 earns the difference in price.

Stainless galls, and brass does not. Stainless threads can cold-weld to each other under assembly pressure, and a galled joint is destroyed on disassembly — the fitting comes off in pieces or not at all. Use an anti-seize or a PTFE-based thread compound on every stainless-to-stainless joint, go on steadily rather than in repeated bites, and avoid backing a joint off and retightening it.

Reducing coupling or hex bushing. Both step a size down and they are not interchangeable. A reducing coupling is female on both ends, so it lands between two lengths of pipe. A hex bushing is male on the large end and female on the small, so it threads into a fitting that is already in place — a tee, a valve, a tank port. Pick by what is on the end you are landing on.

Union where you will need to break the line. A threaded run cannot be taken apart in the middle without unscrewing back to the end. Put a union at the pump, the valve or the piece of equipment that will eventually be serviced, and the next person can pull it without cutting.

Related: Brass fittings · Compression fittings · Dielectric fittings · Y-strainers