Did you know

PEX and plastic supply pipe

• PEX tubing can still be bent by hand at temperatures as low as -40°F. (source: Plastics Pipe Institute and Plastic Pipe and Fittings Association) PEX pipe
• PEX use in residential plumbing rose from under 10% in 1997 to more than 60% as of 2016, according to figures cited by the Plastics Pipe Institute. (source: Plastics Pipe Institute) PEX pipe
• The chemical method behind PEX-A tubing was developed in 1968 by German inventor Thomas Engel, which is why it is called the Engel method. (source: Uponor) PEX-A pipe
• PEX-B gets its cross-links after extrusion, when the tubing is cured in steam or a hot-water bath. (source: Plastics Pipe Institute) PEX-B pipe
• PEX-C tubing is cross-linked only after it has been formed, by exposing the extruded polyethylene tube to high-energy electrons. (source: Plastics Pipe Institute) PEX-C pipe
• CPVC plastic water pipe has been used for drinking-water plumbing since 1959. (source: Plastics Pipe Institute) CPVC pipe
• Polyvinyl chloride is turned into CPVC by a chlorination reaction that is started with ultraviolet light. (source: Plastics Pipe Institute) CPVC pipe
• PP-R pipe joints are made by melting the pipe and fitting together, with a socket-fusion tool running at about 500°F. (source: Aquatherm) PP-R pipe
• In certain hot, fast-flowing recirculation systems, copper dissolved from copper tube can speed the breakdown of PP-R pipe downstream. (source: Plastics Pipe Institute) PP-R pipe
• Since a 2021 revision, the AWWA standard for polyethylene water service tubing allows just one wall ratio, SDR 9. (source: Plastics Pipe Institute) Polyethylene water service pipe

Metal pipe

• Type M copper is sold only as hard straight lengths, while types K and L also come as soft coils up to 100 ft long. (source: Cerro Flow Products) Copper pipe types K, L and M
• Copper tube makers publish pressure ratings for annealed tube because the heat of soldering softens hard tube near each joint. (source: Mueller Streamline Co.) Copper pipe types K, L and M
• Copper drainage tube made to ASTM B306 is sold only in the hard temper, never in soft coils. (source: Cerro Flow Products) Copper DWV pipe
• Galvanized water pipe that once sat downstream of a lead service line can keep releasing lead years after the lead line is gone. (source: U.S. Environmental Protection Agency) Galvanized steel pipe
• Cast iron hub-and-spigot pipe comes in two wall classes whose outside diameters differ, so Service and Extra Heavy pieces need an adaptor to join. (source: Cast Iron Soil Pipe Institute) Cast iron drain pipe
• In a traditional series layout of rigid gas pipe, gas pressure after the meter is typically less than 1/2 psi. (source: Gastite Division) Black steel gas pipe
• One bonding clamp is enough for an entire yellow CSST system, but it may never be clamped onto the corrugated tubing itself. (source: International Code Council) CSST gas tubing
• Black arc-resistant CSST is marked with the letters "AR" so inspectors can tell it apart from yellow tubing. (source: International Code Council) CSST gas tubing
• EPA's quick check for a lead service line needs only a penny or key and a magnet. (source: U.S. Environmental Protection Agency) Lead pipe and lead service lines
• Under EPA's 2024 rule, homes with lead lines are sampled at both the first and the fifth liter, and the higher reading counts. (source: U.S. Environmental Protection Agency) Lead pipe and lead service lines
• Lead-free brass made for drinking water often replaces lead with bismuth, or with bismuth and selenium. (source: Health Canada) Brass fittings and dezincification

Drain pipe and retired pipe

• A 2 in Schedule 40 PVC pipe rated 280 psi at 73°F keeps only 62 psi of that rating at 140°F. (source: Charlotte Pipe and Foundry Co.) PVC Schedule 40 pipe
• Sunlight degrades PVC pipe only to a depth of about 0.001 to 0.003 in, and the effect stops when the exposure stops. (source: Charlotte Pipe and Foundry Co.) PVC Schedule 40 pipe
• Schedule 40 and Schedule 80 PVC of the same size have identical outside diameters, so a 1/2 in Schedule 80 pipe has a bore about 0.08 in narrower. [1] (source: Charlotte Pipe and Foundry Co.) PVC Schedule 80 pipe
• Cutting threads into Schedule 80 PVC halves its pressure rating compared with a solvent-cemented joint. (source: Charlotte Pipe and Foundry Co.) PVC Schedule 80 pipe
• Foam-core PVC drain pipe has the same outside diameter and wall dimensions as solid-wall pipe, but its middle layer is foamed plastic. (source: Charlotte Pipe and Foundry Co.) PVC DWV and foam-core pipe
• In a drain line, solid-wall PVC is somewhat quieter than foam core because noise transmission follows the density of the pipe wall. (source: Charlotte Pipe and Foundry Co.) PVC DWV and foam-core pipe
• One maker's composite drain pipe is black ABS built around a PVC core, combining both plastics in a single wall. (source: Charlotte Pipe and Foundry Co.) ABS pipe
• ABS drain pipe is joined with a cement that needs no primer, unlike PVC. (source: Charlotte Pipe and Foundry Co.) ABS pipe
• The 1995 Cox v. Shell Oil settlement, approved by a county chancery court in Tennessee, committed $950 million to replacing leaking polybutylene plumbing nationwide. (source: United States Court of Appeals for the Fifth Circuit) Polybutylene pipe
• Polybutylene was so hard to spot that its stubs at sinks and toilets were often copper, joined to the plastic through adapters out of sight. (source: Water Resources Research Center) Polybutylene pipe
• In one community of 34,000 homes, Kitec's high-zinc brass fittings were leaking within three to six years of installation. (source: American Academy of Forensic Sciences) Kitec pipe
• Dezincified brass can grow mounds of zinc oxide inside a fitting that choke off the water flow. (source: American Academy of Forensic Sciences) Kitec pipe
• Orangeburg sewer pipe often rots from the inside out, so a line can keep a round outer shape while its inner layers have already failed. (source: City of Ann Arbor) Orangeburg pipe
• Fiber sewer pipe caught on during World War II because cast iron and other metals were scarce and rationed. (source: City of Ann Arbor) Orangeburg pipe

Joining methods

• One push-fit maker allows plain water as a lubricant when pushing tube into its fittings but forbids every other lubricant. (source: NIBCO Inc.) Push-fit fittings
• A single push-fit fitting made to ASSE 1061 can be designed to accept more than one kind of tube, such as copper, CPVC, PEX and PE-RT. (source: Plastics Pipe Institute and Plastic Pipe and Fittings Association) Push-fit fittings
• One maker's PEX crimp tool sheet gives the same crimped-ring diameter limits for PEX and for older polybutylene pipe installations. (source: Zurn) PEX crimp rings
• A properly crimped 1/2 in copper PEX ring must measure between 0.700 and 0.715 in across, a window of 0.015 in. (source: Zurn) PEX crimp rings
• One maker warns that spray foam insulation and bug spray can damage the plastic fittings used under PEX cinch clamps. (source: Watts) PEX clamp (cinch) rings
• The ratcheting tool used on PEX cinch clamps will not release until the clamp has been fully closed. (source: Plastics Pipe Institute and Plastic Pipe and Fittings Association) PEX clamp (cinch) rings
• The ring in an F1960 PEX expansion joint is itself made of PEX, and it shrinks back onto the fitting along with the tube. (source: Watts) PEX expansion fittings
• One maker's manual PEX expander is turned a quarter turn after each expansion so it does not leave grooves inside the tube. (source: Uponor) PEX expansion fittings
• One maker requires copper tube to be free of surface imperfections, including stamped print lines, where a press valve will seal on it. (source: Viega) Copper press fittings
• With a sealing-element swap, one maker's copper press fittings are approved for low-pressure steam up to 15 psi. (source: Viega) Copper press fittings
• One maker uses a plastic sleeve and no insert for PEX of 3/8 in OD and smaller, but a brass sleeve plus a stainless steel insert from 1/2 in OD up. (source: BrassCraft) Compression fittings
• Without an insert stiffener, plastic tube in a compression joint can creep away from the fitting over time until the joint leaks or blows off. (source: A.Y. McDonald Mfg. Co.) Compression fittings
• The line between soldering and brazing is set by temperature alone: a filler that melts above 840°F turns the same capillary joint into a brazed one. (source: Lucas Milhaupt) Soldered (sweat) joints
• Old 50/50 tin-lead plumbing solder actually melts at a lower temperature than the lead-free 95/5 tin-antimony solder that replaced it. (source: The Harris Products Group) Soldered (sweat) joints
• A properly made solvent weld leaves no glue layer at all: the cement softens pipe and fitting so they fuse into one continuous piece of plastic. (source: Oatey) Solvent-weld joints
• One cement maker's chart lets small PVC joints take pressures above 160 psi after 6 hours at 60–100°F, but asks for 48 hours when the work is done at 0–40°F. (source: Weld-On (IPS Corporation)) Solvent-weld joints
• There is no standard torque or number of turns for tightening an NPT pipe joint; the seal depends on the taper and the sealant. (source: Swagelok) Threaded pipe joints
• A 1/2 in NPT pipe thread measures about 0.83 in across the outside of the male thread. (source: Swagelok) Threaded pipe joints
• In one maker's chart, a 1/2 in PP-R socket fusion joint needs only about 5 seconds of heating, followed by a 2-minute cooling time. (source: Red-White Valve Corp.) Heat-fusion joints
• No-hub couplings were first specified inside the CISPI 301-64T pipe standard and only became a separate standard, CISPI 310, in 1978. (source: Cast Iron Soil Pipe Institute) No-hub couplings
• The neoprene sleeve in a standard no-hub coupling has a molded center stop so both pipe ends meet in the middle of the joint. (source: Cast Iron Soil Pipe Institute) No-hub couplings

Fittings and valves

• A dielectric union does not change the metals or the water; it works by removing just one of the three conditions galvanic corrosion needs, direct metal-to-metal contact. (source: National Institutes of Health) Dielectric unions
• Screwing a metal male thread into a plastic female fitting puts nearly all the stress on the plastic, because the metal end does not compress as it tightens. (source: Charlotte Pipe and Foundry) Transition fittings
• Drain-fitting names count fractions of a circle: a "sixteenth bend" turns 22-1/2°, one-sixteenth of 360°. (source: Charlotte Pipe and Foundry) Fitting shapes: elbows, tees, couplings
• A "fifth bend" in cast iron drain fittings turns 72°, one-fifth of a full circle. (source: Charlotte Pipe and Foundry) Fitting shapes: elbows, tees, couplings
• In the 2018 IPC fitting table, the sanitary tee is the only branch pattern limited to one change of direction: horizontal to vertical. (source: International Code Council) Sanitary tees and wyes
• The federal lead-free rule for plumbing exempts water-main gate valves 2 inches in diameter or larger. (source: U.S. Environmental Protection Agency) Shutoff valves

Sizes, codes and marks

• A 1-1/4 in PVC drain pipe measures 1.660 in across the outside, well over the size in its name. (source: Charlotte Pipe and Foundry) Nominal pipe size, CTS and IPS
• Nominal 3/8 in PEX tubing holds about 54% of the water that 1/2 in tubing holds, so a home-run line can deliver hot water with less waiting. (source: Plastics Pipe Institute and Plastic Pipe and Fittings Association) Pipe sizing basics for houses
• Some drinking-water products carry a "Q" value on the package, a lead test statistic that comes from the NSF/ANSI/CAN 61 lead leaching evaluation. (source: U.S. Environmental Protection Agency) NSF/ANSI/CAN 61
• Until October 2017, a plumbing product marked only "NSF 61" was not thereby certified as lead free; a separate 372 or Annex G mark was needed. (source: U.S. Environmental Protection Agency) NSF/ANSI/CAN 372 (lead content)
• The 2024 Uniform Plumbing Code requires copper-alloy (brass) fittings with more than 15% zinc used in plastic water systems to resist dezincification under NSF/ANSI 14. (source: Plastics Pipe Institute and Plastic Pipe and Fittings Association) NSF/ANSI 14 (plastics piping)
• The Uniform Plumbing Code began in Los Angeles in 1928, 17 years before it was formally published under that name in 1945. (source: IAPMO) Plumbing codes: IPC, UPC and IRC
• The ICC says about 76% of the US population lives where the International Plumbing Code has been adopted. (source: International Code Council) Plumbing codes: IPC, UPC and IRC
• Solder that is not lead free may be put on the US market only if it carries a prominent label saying it is illegal to use in plumbing for drinking water. (source: U.S. Environmental Protection Agency) Lead-free solder
• The 2014 change to "lead free" cut the limit for pipes and fittings from 8% to 0.25% but left solder at 0.2%. (source: U.S. Environmental Protection Agency) Lead-free solder
• The second digit of a PEX tubing code is a sunlight rating: 1, 2 or 3 means it passed testing for 1, 3 or 6 months of UV exposure. (source: Plastics Pipe Institute and Plastic Pipe and Fittings Association) Reading the print line on pipe
• Blue print on copper can mean Type L water tube or ACR refrigeration tube, so the printed type matters more than the color. (source: Copper Development Association) Reading the print line on pipe

Choosing pipe and trouble

• A refrigerator magnet can tell lead from galvanized steel: both are dull gray, but a magnet sticks only to the steel. (source: U.S. Environmental Protection Agency) Identifying the pipes in your house
• Under EPA's lead rules, galvanized pipe that ever sat downstream of a lead service line is classed for replacement too. (source: U.S. Environmental Protection Agency) Identifying the pipes in your house
• The plumbing vents poking through many roofs are often black ABS, which survives sunlight because carbon black in the plastic screens out UV. (source: Plastics Pipe Institute) Which pipe for which job
• A frozen pipe builds dangerous pressure only after two ice plugs trap liquid water between them. (source: Plastics Pipe Institute) Frozen pipes by material
• In testing, water in a 2 in soft copper tube was frozen eleven times before the tube burst. (source: Copper Development Association) Frozen pipes by material
• PEX makers set their sunlight limits using central Arizona, the worst-case North American location for UV energy. (source: Plastics Pipe Institute and Plastic Pipe and Fittings Association) Sunlight and UV limits for plastic pipe
• Sunlight changes PVC, CPVC and ABS only to a depth of about 0.001 to 0.003 in, and the change stops when the pipe is shaded. (source: Charlotte Pipe and Foundry) Sunlight and UV limits for plastic pipe
• A frozen pipe may already be cracked and start leaking only after it thaws. (source: Texas A&M AgriLife Extension) Burst pipe: first steps
• In a study of Santa Fe, New Mexico, 95% of copper pinhole leaks were in cold-water lines, and microbes were found deep inside the pits. (source: T. D. Burleigh) Pinhole leaks in copper pipe
• Leftover soldering flux inside copper tube can start pitting, and overheated joints make it worse. (source: Copper Development Association) Pinhole leaks in copper pipe