Cast vs Wrot Copper Fittings: What Actually Differs

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Two bins at the supply house, both marked 1/2-inch 90. One says WROT. One says CAST. They cost different money, and nobody behind the counter is going to explain the difference unless you ask.

Quick answer from a licensed plumber: the words describe how the fitting was manufactured, not how good it is. A wrot fitting is formed from copper tube stock and is commercially pure copper. A cast fitting is poured from a copper alloy — a bronze — and that alloy is where the lead question lives. For ordinary potable-water soldering in standard shapes, wrot is what you want and usually what is on the shelf. Cast earns its place where the shape cannot be made from tube: threaded, flared, flanged and most drainage bodies.

At a glance

The words describe a manufacturing process, not a quality grade

“Wrot” is the trade’s spelling of wrought, and wrought means worked — formed from an existing piece of metal rather than poured into a mold. You can see this directly in what the manufacturers list as their raw material. Elkhart Products’ submittal sheet for solder copper fittings names the material for its wrot line as ASTM B75 Alloy C12200, Seamless Copper Tube. The stock a wrot fitting starts life as is copper tube, which is why a wrot coupling looks like a short piece of pipe with a bulge in the middle. It essentially is one.

Cast fittings start somewhere else entirely. Elkhart lists its cast material as ASTM B584 copper alloy sand castings. Molten alloy, a mold, a finished shape. That is why a cast fitting has that heavier, slightly rough, matte look and a wrot one is smooth and thin-walled.

NIBCO’s own catalog treats these as parallel product families rather than good-and-better. It states that the company “manufactures nine general types of fittings: Wrot Pressure; Cast Pressure; Wrot Drainage; Cast Drainage; Flanges; Flared Tube; Threaded Bronze; Insert Fittings for PEX; Barbed Insert Fittings for Polybutylene,” and adds that “each has its particular place and use and each offers its own advantages when used for the proper service requirement.”

Two standards, and the split is exactly along that line

The standards make the same division. ASME B16.22 is titled Wrought Copper and Copper Alloy Solder-Joint Pressure Fittings, and ASME’s own description says it “establishes specifications for wrought copper and wrought copper alloy, solder-joint, seamless fittings, designed for use with seamless copper tube conforming to ASTM B88 (water and general plumbing systems), B280 (air conditioning and refrigeration service), and B819 (medical gas systems).”

ASME B16.18 is titled Cast Copper Alloy Solder Joint Pressure Fittings, and covers, in its own words, “cast copper alloy solder joint pressure fittings designed for use with copper water tube.” The list of what it establishes is the same list: pressure-temperature ratings, end connection abbreviations, sizes, marking, material, dimensions and tolerances, and tests.

NIBCO’s suggested specification language puts both on the page in the same breath. For wrot: “Material and workmanship shall be in accordance with ASME/ANSI B16.22.” For cast: “Cast Copper Alloy Solder Joint Fittings shall be in accordance with ASME B16.18.”

The pattern continues past pressure fittings, and this is the part that actually tells you when you are holding a casting. Drainage splits the same way — B16.29 for wrought DWV, B16.23 for cast DWV. But three whole families are cast by definition: B16.15 Cast Bronze Threaded Fittings, B16.26 Cast Copper Alloy Fittings for Flared Copper Tube, and B16.24 Bronze Pipe Flanges and Flanged Fittings.

So the practical rule is: if it has pipe threads, a flare seat or a flange on it, you are holding a casting. There is no wrought version of a cast bronze threaded fitting, because you cannot form that shape out of tube. Anything with male or female iron pipe threads gets sealed the usual way, and the choice between tape, dope or putty matters more on a cast body than most people think, because you are torquing against a casting.

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The lead question, which is the one that actually matters

Here is where the difference stops being trivia.

A wrot fitting is commercially pure copper. NIBCO states that its “Wrot Copper Fittings are made from commercially pure copper mill products already meeting current lead-free requirements per ASTM Specifications B75 Alloy C12200.” Elkhart’s material table is blunter still, listing C12200 with the parenthetical (0% Lead). There is no alloy decision to get wrong. It is copper.

Cast is not one material, it is a family, and the family includes leaded alloys. NIBCO’s catalog says its “Cast Fittings are offered in traditional copper alloys C83600, and C84400 and high quality lead-free dezincification-resistant (DZR) silicon bronze alloy C87850 cast or 69300 forged Performance Bronze per ASTM Specification B584.” Elkhart’s material list spells out what that means, alloy by alloy:

• ASTM B584 Alloy C84400 — Copper Alloy Sand Castings for General Applications, marked (>0.25% Lead)
• ASTM B584 Alloy C89833 — Copper Alloy Sand Castings, marked (< 0.25% Lead)

That 0.25% figure is not arbitrary. NIBCO defines it in a footnote: “Lead Free refers to the wetted surface of pipe, fittings and fixtures in potable water systems that have a weighted average lead content” of 0.25% or less.

Both of those cast alloys are legitimate products. One is for general applications and one is for potable water, and the same manufacturer sells both. The takeaway is not that cast fittings are bad — it is that with cast, you have to read what alloy you bought, and with wrot you do not. If a cast fitting is going into drinking water, confirm it is a lead-free alloy and third-party certified. NIBCO’s spec language for that certification is “third party certified to NSF/ANSI/CAN-61.”

The same reasoning applies to the cast brass bodies you already have in the house. Angle stops are castings too, and the lead-free question there is identical — worth knowing when you are choosing under-sink shut-off valves.

Is one stronger? Not according to either manufacturer’s own tables

This is the claim you will see repeated everywhere, and I went looking for the numbers behind it.

I could not find them, and the reason is interesting: neither NIBCO nor Elkhart publishes separate pressure ratings for cast versus wrot solder-joint pressure fittings. Both publish a single internal pressure-temperature table for copper fittings, and it is indexed by tube size, not by manufacturing method. NIBCO’s table gives a 1/2-inch fitting 722 psi across the −20°F to 100°F range; Elkhart’s gives 720 psi for the same size and range. Same table, same numbers, rounding aside, with no cast-versus-wrot column anywhere in it.

NIBCO does publish a separate rating table for cast copper alloy flanges and flanged fittings — but those are Class 125 and Class 150 flanges, a different product with a different failure mode, not a cast elbow versus a wrot elbow.

I am also not going to give you a wall-thickness or bore-smoothness comparison, because no source I opened prints one. The commonly repeated claim that cast fittings are thicker-walled and rougher inside is plausible from handling them, but it is not something either manufacturer publishes a figure for, and this site does not import numbers it cannot point at.

The joint is rated by the solder, not by the fitting

If you want the number that actually limits a soldered copper system, it is not on the fitting at all. NIBCO publishes a table of rated internal working pressures for joints made with copper water tube and solder-type fittings, and the row you land on is chosen by joining material:

• Alloy Sn50, 50-50 tin-lead solder, 1/8-inch through 1-inch at 100°F: 200 psi
• Alloy Sb5, 95-5 tin-antimony solder, same sizes, same temperature: 1090 psi

Same tube. Same fitting. More than five times the rated working pressure, decided entirely by what came off the spool. And note the direction: at 200 psi the 50-50 joint is the weakest link in a system whose 1/2-inch fittings are rated 722 psi, while the 95-5 joint carries a footnote stating that “the solder joint exceeds the strength of Types L & M tube in drawn temper and Type K tube in annealed temper.” The joint stops being the weak point.

Before anyone reaches for the 50-50 numbers: you cannot use it on drinking water. NIBCO’s own note says “The Safe Drinking Water Act Amendment of 1986 prohibits the use of any solder having a lead content in excess of 0.2% in potable water systems.” Elkhart’s sheet carries the identical note. Those tin-lead rows are there for the legacy systems and non-potable work, and they are a useful reminder of how much the filler metal is doing.

Two more numbers from the same catalog, both about workmanship rather than parts. NIBCO cites National Bureau of Standards report BMS58 on soldered joints in copper tubing: “When the clearance is greater than 0.010 inch (0.25 mm), there is difficulty in filling the joint properly.” And on penetration depth, testing 3/4-inch Type K, solder reaching one-third of the cup depth gave a breaking load of approximately 2,100 lb, against approximately 7,000 lb for penetration of the entire cup.

That is a factor of more than three, and it has nothing to do with which bin the fitting came from. If your joints are failing, the fitting is almost never the reason. Prep is.

So which do you buy?

For everyday potable-water soldering — couplings, elbows, tees, adapters — buy wrot. It is pure copper, so the lead question never arises, it is thinner-walled and heats faster on the torch, and it is what most suppliers stock in the standard shapes anyway. Elkhart notes its 1/8-inch through 8-inch fittings are made in the United States at Elkhart and Geneva in Indiana and Fayetteville in Arkansas, if domestic sourcing matters to your spec.

Buy cast when the shape requires it. Threaded adapters, flared fittings, flanges, drainage bodies and valve bodies are castings because they cannot be anything else. That is not a compromise, it is the correct product for the geometry.

Read the alloy on any cast fitting going into drinking water. C84400 and C89833 are both sold by the same manufacturer and only one of them is under the lead-free threshold. This is the single practical difference worth carrying out of this article.

One footnote for larger work: Elkhart’s 5-inch, 6-inch and 8-inch fittings are not formed the same way as the small ones. They are “electrically welded using silicone bronze” to produce an MSS SP-109 compliant product, with each fitting “individually tested with air under water.”

And if the job you are actually pricing is a repair rather than a build, the fitting family is rarely the decision. Whether to solder at all is — that is the real fork on a pinhole leak in copper pipe, and the honest comparison is push-to-connect against soldered copper. On the commercial side, the equivalent question is press versus brazing.

Frequently asked questions

What does wrot mean on a copper fitting?
Wrot is the trade spelling of wrought, and it means the fitting was formed from copper tube stock rather than poured into a mold. Manufacturers list the raw material as ASTM B75 alloy C12200 seamless copper tube.

Are cast copper fittings lead-free?
Some are and some are not, and you have to read the alloy. Elkhart lists ASTM B584 alloy C84400 as greater than 0.25% lead and alloy C89833 as less than 0.25% lead. A wrot fitting is commercially pure copper, so the question does not arise.

Is cast or wrot stronger?
Neither NIBCO nor Elkhart publishes separate pressure ratings for cast versus wrot solder-joint pressure fittings. Both publish one internal pressure-temperature table indexed by tube size, giving a 1/2-inch fitting roughly 720 psi at up to 100 degrees Fahrenheit.

What is the difference between ASME B16.18 and B16.22?
B16.18 covers cast copper alloy solder joint pressure fittings and B16.22 covers wrought copper and copper alloy solder-joint pressure fittings. They are the same standard written for the two manufacturing methods.

Does the fitting or the solder set the pressure rating of a joint?
The solder does. In NIBCO’s table a 1/8-inch through 1-inch joint at 100 degrees Fahrenheit is rated 200 psi with 50-50 tin-lead solder and 1090 psi with 95-5 tin-antimony, on the same tube and the same fitting.

Bottom line

Cast and wrot are two manufacturing routes to the same catalog, not two quality tiers. Wrot is formed from copper tube and is pure copper; cast is poured from a bronze alloy and comes in leaded and lead-free versions. Buy wrot for ordinary solder work, buy cast when the shape demands it, and read the alloy on anything cast that will carry drinking water. Then stop worrying about the fitting and go clean the joint properly — the published numbers say that is where the strength actually comes from.

Sources

• ASME, B16.18 — Cast Copper Alloy Solder Joint Pressure Fittings, standard title and scope.
• ASME, B16.22 — Wrought Copper and Copper Alloy Solder-Joint Pressure Fittings, standard title and scope. Neither ASME page publishes numeric pressure-temperature ratings.
• NIBCO INC., Copper Fittings catalog engineering section (revised 4/11/2024) — fitting families, materials and specification language, rated internal working pressures for copper fittings and for solder-type joints, NBS report BMS58 clearance finding, and solder penetration breaking loads.
• Elkhart Products Corporation, Solder Copper Submittal, 2014 Rev B — product description, standards list, alloy-by-alloy material table with lead content, large-diameter welded construction, and internal pressure-temperature ratings for copper fittings.

Standards are cited as adopted; section numbers and editions move, so confirm what your jurisdiction has adopted before writing a spec.