White polypropylene NPT-threaded fittings

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Family of 14 white polypropylene (PP) threaded fittings, NPT pattern (ASME B1.20.1): bushing, 90° elbow, street elbow, coupling, cross, barrel nipple, reducing nipple, wall-pass sleeve, 45° elbow, cap, plug, tee, union and union fitting, 1/2″ to 2″ depending on the figure. A thermoplastic for cold and hot water up to 82 °C (180 °F) continuous service, resistant to acids and alkalis, not suitable for chlorinated or aromatic solvents. The NPT thread is not interchangeable with the BSP thread of PP systems imported from Argentina and Brazil.

SKU VT-59256 (90° elbow) · family of 14 NPT-threaded white polypropylene references · price from $1,300 COP + VAT per unit depending on figure and size (Jul 2026, confirmed on quotation)

1. Technical specifications

Figures and available sizes (TECTUL catalog, Jul 2026)

The sizes listed are those published per figure in the catalog as of July 2026; stock and reducing combinations are confirmed on quotation. Body manufacturing dimensions (center-to-end, overall length, thickness) follow the manufacturer's standard: unlike metallic fittings (ASME B16.3, B16.11), there is no public dimensional standard for the threaded PP fitting, so they are supplied on quotation and not published here.

NPT thread data by size (ASME B1.20.1)

Taper NPT thread per ASME B1.20.1: 60° flank angle, 1:16 taper (3/4 in per foot) measured on diameter. L2 is the effective (hand-tight) thread length defined by the standard. These thread data are identical to those of any metallic NPT fitting: white PP mates with NPT pipe and fittings in steel, malleable iron or threaded PVC from the catalog.

Material

Body	Injection-molded polypropylene (PP), white. The color is a commercial convention of the Colombian market for threaded plumbing PP; no standard mandates it.
Density	0.900–0.905 g/cm³ (56.2–56.5 lb/ft³) — the lowest-density general-purpose thermoplastic; the fitting floats in water.
Tensile strength	30–40 MPa (4,350–5,800 psi) typical for molding grades; homopolymer averages ~15% higher tensile strength than copolymer, while copolymer is tougher on impact and at low temperature.
Melting point	160–166 °C (320–331 °F) for commercial isotactic PP.
Continuous service temperature	82 °C (180 °F) — see section 5.
Resin grade	The supplier's exact resin grade (homopolymer vs copolymer, melt flow index) is manufacturer data and is confirmed on quotation; the properties in this table are base values for commercial PP.

General specifications

Product	Family of 14 white polypropylene NPT-threaded fittings for building water systems: cold and hot water, with no solvent cements.
Joint	NPT threaded on every opening (male or female depending on the figure). The system assembles and disassembles with hand tools; no fusion machine or chemical welding is required.
Size range	1/2″ to 2″ depending on the figure (table above).
Working pressure	No public standard assigns a rating to the NPT-threaded PP fitting: it is confirmed on quotation per the manufacturer — section 2 explains why and which rule governs assembly.
Applicable standards	ASME B1.20.1-2013 (R2018) (NPT threads). The system's declared conformity with NTC 1500 (Colombian plumbing code) and NTC 4897 is manufacturer-stated and confirmed on quotation.

2. The plastic-thread rating: what is known, what is not, and the rule that governs

Why this sheet does not publish a pressure-by-size table

For metallic threaded fittings a standard assigns the rating directly (ASME B16.3 for malleable iron, B16.11 for forged steel). For the NPT-threaded polypropylene fitting no equivalent public standard exists: the allowable pressure depends on the resin grade, on each manufacturer's mold thickness and on temperature, and only the fitting's manufacturer can declare it. The threaded-PP technical dossiers circulating in the region (Argentine and Brazilian systems) publish pressure-temperature tables valid for their own systems, which are moreover BSP-threaded — a different thread (see section 3) and a different mold. Copying those figures onto another manufacturer's NPT fitting would be inventing data. That is why the working pressure by size for this family is confirmed on quotation with the lot manufacturer's data, and this section documents what is verifiable: the mechanics of the joint and the assembly rule that prevents the number-one failure mode.

The mechanics: a taper thread is a wedge inside the female

The NPT thread seals by interference: as it is tightened, the tapered male (1:16) drives into the female and generates hoop stress in it. In a metallic fitting that stress is absorbed by a material with a modulus of ~200 GPa; in polypropylene the modulus is two orders of magnitude lower and the hoop stress grows with every extra turn. The practical consequence, documented by plastic-fitting manufacturers: the number-one failure mode of plastic threading is not service pressure — it is the female split by over-tightening during assembly, a longitudinal crack that appears while tightening or hours later (stress cracking). The risk is highest in small sizes and when a plastic female receives a metallic male, which does not yield.

The tightening rule (the figure that is corroborated)

Tightening	Hand-tight to a firm stop + 1 to 2 wrench turns, never more. It is the concurring instruction of plastic-fitting manufacturers (Spears Manufacturing: "1 to 2 turns beyond finger tight is generally all that is required for a sound plastic threaded connection"; LASCO Fittings publishes the same rule). Over-tightening does not improve the seal: it splits the female.
PTFE tape	2 to 3 wraps on the male, in the direction of the thread (clockwise seen from the pipe end), covering from the first full thread: Boshart Industries specifies 2 wraps of premium tape (with paste) and a minimum of 3 wraps of standard tape on 1/8″ to 2″ NPT. More wraps thicken the male and raise the stress on the plastic female — excess tape is a direct cause of split females.
Alternative to tape	Several plastic-fitting manufacturers prefer, for plastic females, a non-hardening sealant compatible with thermoplastics instead of tape: tape lubricates and makes it easy to over-turn without feeling it. If paste is used, it must be declared PP-compatible (some compounds attack thermoplastics through chemical stress cracking).
Tool	Strap or band wrench. A toothed pipe wrench bites into and cracks the plastic body.

The system's working pressure is set by the weakest element in the line and by the service temperature (the hotter, the lower the allowable pressure in any thermoplastic). The numerical figure by size for this family belongs to the manufacturer and is supplied on quotation; TECTUL does not publish pressure figures without a verifiable source.

3. NPT vs BSP in polypropylene: the buying trap that catches 2 threads and drips

Threaded PP sold in Colombian hardware stores is NPT pattern (North American, ASME B1.20.1); threaded PP imported from Argentina or Brazil is BSP pattern (Whitworth, ISO 7 / BS 21). They look identical to the eye, yet they do not seal together: mixing them produces the classic field symptom — it catches 2 threads, jams, and drips in a spiral along the thread. It is this family's most common cause of returns and no catalog table warns about it.

The three differences that prevent the seal

Flank angle	NPT: 60° · BSP: 55°. Even where the pitch matches, the flanks do not seat face against face: contact is along lines, not surfaces, and the fluid finds a continuous helical channel (the "spiral leak").
Thread form	NPT: flat truncated crests and roots · BSP: rounded crests and roots. The root geometry does not mate even where the pitch is equal.
Threads per inch	They coincide at 1/2″ and 3/4″ (14 in both systems — which is why there it "almost fits") and diverge from 1″ up: NPT 11.5 vs BSP 11. With different pitch, the male advances 2–3 threads and jams.

Detection table by size

How to verify before assembling: (1) count threads over one inch — 11 threads on a 1″ or larger size gives BSP away; (2) a 55°/60° thread gauge on the sizes where the pitch coincides; (3) origin — Argentine and Brazilian PP systems (the regional threaded-PP technical dossiers that dominate Spanish-language search) are BSP from the factory. PTFE tape does not fix an NPT/BSP mix: it fills the gap on day one and drips with pressure and temperature cycles. The TECTUL blog guide on NPT threads ("Rosca NPT explicada") covers the NPT pattern in detail; every reference in this sheet is NPT and mates with the others and with the rest of the NPT-threaded catalog (steel, malleable iron, threaded PVC).

4. Polypropylene chemical compatibility (service summary)

Polypropylene is among the thermoplastics most resistant to aggressive aqueous media — and among the most vulnerable to non-polar organic solvents. Concurring summary from resin-maker and laboratory chemical-resistance charts (at 20–23 °C unless noted):

Dilute inorganic acids (hydrochloric, sulfuric, phosphoric)	Resistant. PP withstands aqueous solutions of nearly all inorganic acids, even at high concentrations and above 60 °C.
Alkalis (caustic soda, potash, aqueous ammonia)	Resistant, even concentrated.
Inorganic salts in aqueous solution	Resistant.
Alcohols (ethanol, isopropanol)	Resistant.
Concentrated oxidizing acids (fuming nitric, oleum, chromic acid)	Not suitable. Strong oxidizers degrade PP.
Halogens and chlorinated oxidizers (wet chlorine, concentrated hypochlorite)	Not suitable for continuous service.
Chlorinated solvents (trichloroethylene, carbon tetrachloride, dichloromethane)	Not suitable. Swelling and property loss; worsens with temperature.
Aromatic hydrocarbons (benzene, toluene, xylene)	Not suitable. PP swells cold and dissolves in hot aromatics (xylene dissolves it at high temperature).
Fuels (gasoline, diesel)	Limited service: moderate attack that grows with temperature and contact time — not recommended continuously.

This table guides preselection using the concurring categories of Braskem's PP chemical-resistance technical bulletin and laboratory compatibility charts. For real chemical service, suitability is verified against the specific reagent, concentration and temperature of the process before purchasing — PP's chemical resistance drops markedly above 60 °C in several media.

5. Polypropylene service temperature

Maximum continuous service	82 °C (180 °F) — a design value concurring between commercial PP datasheets and the system's declared use (cold and hot water). Some sources quote up to 100 °C for specific grades without mechanical load; 82 °C is the conservative value applicable to a pressurized fitting.
Melting point	160–166 °C (320–331 °F) for commercial isotactic PP. Between 82 °C and melting the material does not fail suddenly: it loses stiffness progressively, and with it pressure capacity.
Temperature effect on pressure	Like every thermoplastic, PP's allowable pressure falls as temperature rises: modulus and strength decrease continuously from room temperature. Any pressure figure must state its temperature — a bare rating is not a datum.
Low temperature	PP homopolymer embrittles below ~0 °C; copolymer keeps impact toughness at low temperature (the reason fitting systems are usually molded in copolymer). The supplier's grade is confirmed on quotation.
Fluid freezing	Water freezing inside the fitting bursts it by expansion, as with any rigid fitting: in high-altitude outdoor exposure the line is protected or drained.

6. Frequently asked questions

What is the difference between NPT and BSP threads in plastic fittings?

NPT (ASME B1.20.1, North American pattern) has a 60° flank angle with flat crests, and BSP (ISO 7 / BS 21, Whitworth pattern) 55° with rounded crests; the pitch also differs from 1″ up (NPT 11.5 threads/in vs BSP 11). They do not seal together: the mix catches 2 threads, jams and drips in a spiral, and PTFE tape does not fix it. Colombian threaded PP is NPT; PP imported from Argentina or Brazil is BSP.

How many turns do you tighten a threaded polypropylene fitting?

Hand-tight to the stop plus 1 to 2 wrench turns, never more — the concurring instruction of plastic-fitting manufacturers (Spears, LASCO). Over-tightening is the number-one failure mode: the taper thread acts as a wedge and splits the plastic female, sometimes hours after assembly.

What working pressure does a threaded polypropylene fitting take?

No public standard assigns a rating to the NPT-threaded PP fitting (unlike malleable iron, with ASME B16.3): the allowable pressure depends on the resin grade, the manufacturer's mold and the temperature, and is confirmed on quotation with the manufacturer's data. The threaded-PP pressure-temperature tables circulating in the region belong to other manufacturers' BSP systems and are not transferable.

Is white polypropylene suitable for hot water?

Yes, up to 82 °C (180 °F) continuous service — it covers domestic hot water. Its melting point is 160–166 °C, but above 82 °C stiffness (and with it pressure capacity) drops progressively.

Does polypropylene resist chemicals?

It resists inorganic acids and alkalis even concentrated, and salt solutions, but not chlorinated solvents, aromatic hydrocarbons (benzene, toluene, xylene) or strong oxidizers — the table in section 4 summarizes service by chemical family.

7. Application notes

8. Technical notice and limitation of liability