Pipe joining methods field guide: solder, press, and solvent weld

The joint is where the pipe fails

Pipe joining is how you bond two pieces of pipe into one sealed connection. The pipe itself rarely fails. A straight stick of copper or PVC will sit in a wall for fifty years and never leak in the middle. The joint is the weak point, every time, because the joint is where the material changes, where the geometry changes, and where the workmanship lives. Walk a system that is weeping and you will find the problem at a fitting, not in the field of a pipe.

The method is not a free choice. It is set by three things at once: the material you are joining, the pressure and the service the line carries, and the code the jurisdiction adopted. Copper solders, brazes, or presses. PVC and CPVC solvent weld. Steel threads or grooves. PEX crimps, cinches, expands, or pushes. HDPE fuses with heat. You do not get to bring a torch to plastic or glue to steel, and you do not get to use a method the listing does not cover for that material.

Which pipe you run is a separate decision with its own tradeoffs, covered in the piping materials guide. This guide is the other half: once the material is on the truck, how you make the joints hold. The two decisions are joined, because the joining method is part of why you picked the material in the first place.

How do you choose a joining method?

Choose the joining method by working three things against each other: the pipe material, the pressure and temperature of the service, and what the adopted code and the listing allow. The material narrows it first, because each material has a short list of methods that bond it at all. Then the service decides among them. Then the code and the AHJ can rule one out before you do.

Service is the part crews skip. A potable cold-water branch, a hot recirculation main, a medical gas line, a fire sprinkler riser, and a buried gas main are five different duties, and each one rewards a different joint even on the same size pipe. High temperature and high pressure push you toward the stronger joint. A finished, occupied space pushes you away from a flame. A buried line pushes you toward a joint with no fitting to leak, which is why fusion owns that work.

The matrix below is the starting point, not the answer. The right method on any given run is the one that is listed for that material, rated for that service, accepted by that jurisdiction, and within the skill your crew actually has. A crew that brazes all day will make a better braze than a press they learned last week, and the reverse is just as true.

How do you solder copper pipe?

Soldering, called sweating in the trade, joins copper by heating the fitting and drawing molten solder into the gap between the tube and the fitting socket by capillary action. The solder does not fill a void. It wicks into a thin, even space and freezes there, and a sound joint shows a full ring of solder all the way around the cup. The work is five steps and there is no shortcut in any of them: clean, flux, heat, feed, wipe.

Clean the tube end and ream the fitting socket to bright metal with sand cloth or a fitting brush, because solder will not bond to oxide, dirt, or oil. Brush a thin film of flux on both surfaces to keep them clean as they heat and to pull the solder in. Heat the fitting, not the solder, until the joint is hot enough to melt solder on contact, then touch the wire to the joint and let capillary action carry it around. Wipe the hot joint with a rag to clear the flux residue, because aggressive flux left to pool inside the line corrodes the copper right where it sat.

Three things wreck a solder joint, and they all look fine for a week. A dirty or unfluxed joint never bonds and lets go under pressure. An overheated joint burns the flux off before the solder flows, so it beads up instead of wicking in. And water in the line is the classic killer: the trickle carries the heat away, the joint never reaches temperature, and you get a cold, grainy joint that holds at rough-in and weeps in service. Drain the line, plug a weeping trickle with a soluble plug or bread, and if you cannot get it dry, press it instead.

Use lead-free solder on any potable water line, no exception. The Safe Drinking Water Act has banned lead solder on drinking water for decades, and the lead-free rule caps solder and flux at 0.2 percent lead, against the 0.25 percent weighted average that governs the wetted surfaces of fittings and fixtures. The common lead-free solders are tin based and want a touch more heat and a cleaner joint than the old lead solder did, so the cleaning step matters more, not less.

Brazing copper, and the nitrogen purge

Brazing joins copper with a filler metal that melts above about 840 F, far hotter than solder, and the result is a stronger joint that holds higher temperature and higher pressure. The brazing rods used in plumbing, refrigeration, and medical gas run above 1,000 F. That heat is the whole point. A brazed joint is closer to a weld than to a soldered one, and it is the method for refrigeration lines, high-pressure mechanical piping, and medical gas, where a solder joint is not rated for the duty.

The difference from soldering is heat and filler, but the discipline is different too. Some brazing alloys are self-fluxing on copper-to-copper joints and some need flux, and the high heat means you control the flame and the dwell so you flow the filler without melting the base tube. The joint clearance still has to be right, because brazing relies on capillary draw the same way soldering does. It is hotter, stronger, and less forgiving of a sloppy fit.

On refrigeration and medical gas the rule that catches people is the nitrogen purge. You flow a low rate of dry nitrogen through the tube while you braze, commonly a few cubic feet per hour, so the nitrogen displaces the oxygen inside. Without it, the high heat forms a black cupric oxide scale on the inside wall, and that scale flakes off and travels with the refrigerant or the gas, plugging metering devices, reversing valves, and small orifices downstream. Medical gas brazing carries its own purge, qualification, and verification regime under NFPA 99, with certified installers and a separate test, and that work is covered by topic in the medical gas piping material. Do not braze a med-gas line off a plumbing habit.

What is a press fitting?

A press fitting is a copper, stainless, or PEX fitting with a rubber O-ring seated in a bead at the cup, joined by a powered tool that crimps the fitting permanently onto the tube. There is no flame. You cut and deburr the tube, mark the insertion depth, push the tube fully home, set the right jaw over the bead, and squeeze, and the tool deforms the fitting and the O-ring into a sealed connection in a couple of seconds. A joint that would take twenty to thirty minutes to solder presses in under five.

The seal is usually an EPDM O-ring for water, with other compounds for fuel gas and other service, so the fitting has to match the duty. Two things make or break the joint. Insertion depth: push the tube short of the stop and the O-ring lands wrong, so mark the depth and confirm the mark disappears into the cup before you press. The O-ring itself: a burr or grit on the tube end nicks it and the joint weeps, which is why deburring is not optional.

The one that bites on a big job is the joint nobody pressed. An unpressed press fitting looks exactly like a pressed one until the system comes up to pressure, and on hundreds of joints it is easy to miss one. Most systems build in a leak-detection feature that weeps at a low test pressure on an unpressed joint on purpose, so you find the miss before close-in. Walk every joint at the test, every time, and look for weeping or green discoloration at the tube-to-fitting line.

Press has taken over occupied-building and commercial water work for one reason above the speed: no torch. No flame means no fire watch, no hot work permit, and no chance of setting a wall cavity smoldering. It also joins a wet line, so a repair you cannot fully drain is no obstacle. The fittings cost more than solder, but on a job with hundreds of joints inside a finished space, the labor and the absence of fire risk pay for them.

What is solvent welding?

Solvent welding is how you join PVC, CPVC, and ABS, and it is not gluing. The primer and cement chemically soften the surfaces of the pipe and the fitting and fuse them into one piece of plastic as the solvent flashes off. Done right, there is no separate adhesive layer holding two parts together. The two parts become one. That is why a sound solvent weld is as strong as the pipe and a bad one fails at the joint.

On most pressure systems it is a two-step process under ASTM D2855: a primer conforming to ASTM F656 that cleans and softens the surface, then a cement that does the welding. Cut the pipe square, deburr and chamfer the end, dry-fit to check the depth, then primer on both the pipe end and the fitting socket, cement on both while still wet, push together with a quarter turn to spread it, and hold the joint a few seconds so it does not push back out. A proper joint shows a continuous bead of cement around the shoulder.

The cement has to match the material, and this is a real failure on the truck. CPVC cement conforms to ASTM F493, PVC cement to ASTM D2564, and ABS has its own. PVC cement on a CPVC joint will not make a weld rated for the hot water and pressure CPVC carries. Use the cement labeled for the material you are joining, and use the primer the system calls for unless it is a listed one-step product that does not require it.

Cure time is not optional and it is not fixed. The joint sets in minutes but needs hours of cure before it sees pressure, and how long depends on pipe size, temperature, and humidity, longer when it is cold or damp. The cement label carries the cure schedule for that product against size and temperature, and that is the number that governs, not the clock in your head. The errors that fail a system are predictable: no primer where the system needs it, too little cement so the weld is starved, too much so it pools and weakens the pipe, and pressurizing a green joint before it cures, which blows it apart or leaves it weeping.

Threaded joints and pipe thread sealant

Threaded joints use a tapered national pipe thread, NPT, that wedges tighter as you assemble it. The taper gives the mechanical grip, but the threads alone do not seal, because a small spiral void runs along the thread crests and roots. You fill that path with a sealant: PTFE tape wrapped on the male threads in the direction of the thread, or a pipe joint compound, the paste the trade calls pipe dope, or both on larger or higher-pressure connections. Tape helps assembly and the initial seal, dope fills the gaps and lubricates the joint.

Threaded work is the method for steel and brass at fixtures, valves, gas, and smaller mechanical connections, and for the transition from a plastic or copper system onto a threaded device. Pipe dope is often the better choice on brass and stainless, which carry coarser threads, and tape is safe across materials. The sealant is not glue. It seals the spiral leak path, so a thread that was cut clean and made up to the right tightness holds.

Both over and under tightening fail a threaded joint. Under tighten and the spiral path never closes and it weeps. Over tighten, especially on stainless or on a plastic male thread run into a metal fitting, and you split the fitting or gall the threads. A plastic-to-metal thread goes hand tight plus a turn or two with the sealant the manufacturer specifies, not cranked down with a wrench, because the plastic cracks long after you leave. Make it up firm, not gorilla tight, and stop where the manufacturer says.

Grooved mechanical couplings

A grooved coupling joins large steel pipe fast with a gasket and a two-segment housing instead of a weld or a thread. You cut or roll a groove into the pipe ends, wrap a pressure-responsive gasket around the joint, set the segmented housing over the gasket so its keys seat in the grooves, and bolt the segments together. The gasket seals, the housing keys lock the pipe ends against pull-out, and the joint is made. The coupling, the groove, and the gasket all conform to AWWA C606 for grooved and shouldered joints, with the housings commonly ductile iron and the gaskets an elastomer matched to the service.

The groove is cut two ways. A roll groove cold-forms the groove into the pipe wall with a rolling tool and suits standard and lighter wall pipe. A cut groove machines the groove out of the wall and suits heavier wall and higher pressure. The pipe wall, the pressure, and the size decide which one, against the manufacturer's listed dimensions, and a groove cut out of spec is the common reason a grooved joint leaks or pulls.

Grooved is the workhorse on large commercial mechanical and fire piping, because it is far faster than welding steel and needs no flame. A flexible coupling lets the joint take a small amount of angular and axial movement, which absorbs thermal growth and building movement and makes the system easier to service: unbolt a coupling and a section comes out without cutting the pipe. That speed, the no-hot-work installation, and the serviceability are why grooved owns big chilled water, condenser water, and fire main risers. For potable service the gasket has to carry an NSF 61 listing.

Flare and compression joints

Flare and compression are mechanical joints for soft copper and small tube where you want a serviceable connection and no flame. A flare joint cones the tube end out to 45 degrees with a flaring tool, then a flare nut pulls that cone tight against the matching seat of the fitting, metal to metal. It is the joint for gas connections, instrument lines, and equipment hookups where a sound, demountable metal seal is wanted, and it is common on fuel gas and refrigeration service tubing.

The flare has to be formed clean and square. A cracked, off-center, or under-formed flare seats unevenly and leaks, and an over-formed one splits. Use the flaring tool, not a guess, and inspect the cone before you make it up. On gas work the flare nut goes to the makeup the code and the manufacturer specify, and the joint is leak-tested like any gas connection.

A compression joint seals with a ferrule, a small ring that the nut compresses onto the tube to bite and seal as you tighten. It is the quick, demountable joint for fixture stops, supply tubes, and small instrument connections, and it needs no flame and no special tube prep beyond a clean, square, deburred end. The ferrule does the work, so the tube has to be round and the nut made up to the right tightness, firm enough to set the ferrule, not so hard it crushes the tube. Both joints earn their place where you want to take the connection apart again.

How do you join PEX?

PEX joins four ways, all mechanical and all flameless: cold expansion, copper crimp ring, stainless cinch clamp, and push-to-connect. Each has its own ASTM listing, and the fitting, the ring, and the tool have to belong to the same system. The piping materials guide covers how PEX-a, PEX-b, and PEX-c differ and which method suits each, so this is the joining side in short.

Cold expansion, under ASTM F1960, is the PEX-a method: a tool stretches the tube and a reinforcing ring, you slip the fitting in, and the tube's memory shrinks it back tight on the fitting, with no separate ring crimped from outside and a larger bore that restricts flow less. Copper crimp, under ASTM F1807 for metal insert fittings or F2159 for plastic ones, slides a ring over a barbed insert fitting and squeezes it with a calibrated crimp tool. Stainless cinch, under ASTM F2098, uses a clamp with a single ear that a ratcheting tool pinches to a fixed stop, handy in tight spots where a crimp jaw will not swing.

PEX fails at the fitting, not the tube, and almost always because the connection was made wrong, not because the system is weak. A crimp ring has to sit square and the right distance from the tube end, and it has to pass the go/no-go gauge that comes with the tool. A cold-expansion fitting has to be given its few seconds to shrink back tight before any pressure goes on it, longer in the cold. Get the ring square and gauged and the joint is as reliable as anything in the trade.

Push-to-connect fittings

A push-to-connect fitting, the SharkBite-style joint, seals with no tool, no flame, and no ring. Inside the fitting a stainless grab ring of teeth bites the pipe to hold it, and an EPDM O-ring seals against it. You cut the pipe square, deburr it, mark the insertion depth, and push it home past the grab ring. It joins copper, PEX, and CPVC with the same fitting, which is exactly why it lives in the repair bag and why it is the fast tie-in when you cannot solder a wet line or wait out a cure.

The catch is reliability and where the code lets you hide it. Push-fit is generally seen as the least durable of the mechanical joints over the long haul, because it leans on an O-ring and a grab ring rather than a fused or crimped connection. The manufacturers list many of these fittings for concealed and even buried use, but that is the manufacturer's listing, not the local rule. A large share of jurisdictions and inspectors want push-fit joints to stay accessible, not buried behind finished drywall or in a slab, and interpretations vary by AHJ. Confirm the adopted code and the inspector before you close a wall over one.

The honest position is to use push-fit for what it is good at. It is a fast, no-tool repair and tie-in joint and a way to join across three materials in one move. For new concealed water distribution, a soldered, pressed, crimped, or solvent-welded joint is the one most shops and most inspectors trust behind the wall. Pressure test the system before you cover any of it, push-fit most of all.

Heat fusion for HDPE and polyethylene

HDPE and other polyethylene pipe are joined by heat fusion, which welds the plastic pipe into a continuous, monolithic line with no fitting at the joint. That is the whole reason fusion owns buried water, gas, and geothermal work: a fused line has no bell, no gasket, and no threaded fitting to leak underground, where a leak is found by a wet spot in the yard and fixed with an excavator. The methods follow ASTM F2620 for heat fusion and ASTM F1290 for electrofusion.

Butt fusion is the common method. A machine squares and faces the two pipe ends, cleans them, and presses them against a flat heater plate held to roughly 400 to 450 F until the ends melt, then pulls the plate, brings the molten ends together under controlled pressure, and holds them while the joint cools and the molecules mix across the seam. Done to the procedure, a fused joint is stronger than the pipe, and a destructive test fails outside the fusion zone, not at it. The variables that matter are the heater temperature, the time, the pressure, and a clean face, and they come from the procedure and the pipe maker, not from feel.

Electrofusion uses a fitting with an embedded heating coil. You clean and scrape the pipe surface, slide the fitting on, and run a controlled current through the coil, which melts and fuses the fitting to the pipe from inside the joint. It suits tie-ins and tight spots where a butt-fusion machine cannot square up to the pipe. Both methods are operator and procedure driven, so qualified fusion technicians and a recorded fusion log are how this work gets accepted on a real project.

No hot work: the fire watch, the firestop, and why press is winning

Open-flame joining is hot work, and on a commercial or occupied building hot work is a permitted, watched, controlled activity, not a casual torch. A hot work permit, a fire watch posted during the work and for a period after, a cleared and protected area, and a fire extinguisher at hand are the standard controls, because the single biggest risk of soldering and brazing is not the joint, it is the fire you start in a wall cavity, a ceiling, or stored material that smolders for an hour after you leave.

That cost is why the flameless methods have taken over so much commercial work. Press on copper, mechanical and crimp on PEX, grooved on steel, and solvent weld on plastic all make the joint with no flame, so there is no permit, no watch, and no fire risk. On a tenant build-out in a live building, the no-hot-work joint can be the reason a contractor wins the bid, because the general contractor would rather not shut down a floor for a torch.

Firestopping ties into this at every rated wall and floor the pipe passes through. The penetration has to be sealed with a listed firestop system, and the sealant has to be compatible with the pipe, which matters for plastic that an incompatible firestop can crack. Keeping the torch out of the building and the firestop right at the penetrations is how a piping job stays out of the fire marshal's report. On data center and other mission-critical mechanical work the same logic runs harder: anywhere water or a flame sits near energized equipment, the flameless joint and the controlled penetration are not a preference, they are the plan.

Dielectric unions and dissimilar metals

Joining two different metals on a water line builds a battery. Copper landed straight onto a steel water heater nipple or galvanized pipe, with water in between, makes a galvanic cell, and the current that flows eats the more active metal, the steel, right at the joint. In aggressive water you can see that joint rusting and weeping inside a year or two. The fix is a dielectric union or dielectric nipple, a fitting with a nonconductive separator that breaks the metallic path so the galvanic current cannot flow.

Both the IPC and the UPC call for a dielectric fitting where dissimilar metals like copper and galvanized steel meet on a water line, so it is required where those metals join, not a nicety. A brass transition is accepted in some cases because brass sits between copper and steel and is more forgiving, but confirm what the adopted code accepts. The piping materials guide covers the corrosion side of this in more depth.

Dielectric unions have their own failure to know about: the insulating washer and the inside of the fitting can scale up in hard water and bridge the gap, quietly reconnecting the metals it was installed to separate. On a hot water heater connection in hard water, a flexible dielectric connector or a brass transition often outlasts a cheap dielectric union that mineralizes shut. Either way, the rule holds. Do not land copper straight onto steel and walk away.

Support the joint so it carries no stress

A joint is sized and made to seal, not to hold the pipe up. Hang and support the pipe so the joints carry the line's weight and movement, not the other way around. A fitting taking the dead weight of an unsupported run, or fighting the thrust of thermal expansion, is a fitting working a duty it was never rated for, and it shows up as a slow weep or a cracked joint months later.

Two things stress a joint: weight and movement. Support each material at its own hanger spacing, which is closer for plastic than for metal, and let long hot runs expand without pinning the pipe, because a clamped plastic line buckles and rubs as it grows and shrinks. Give it the offset or the loop it needs to take up the growth. And do not spring a misaligned pipe into a fitting and rely on the joint to hold the gap closed, because that stored stress lives at the joint for the life of the line. Cut and fit it true, then support it, then make the joint.

How do you test the joints?

A pressure test is how you prove the joints before anything covers them, and the joining method sets when you can test. Copper, soldered or pressed, is ready as soon as the solder cools or the press is made. Solvent-welded PVC and CPVC have to wait out the full cement cure first, because a green weld will not hold pressure, and the cure clock runs longer in cold or damp air. PEX mechanical joints are ready when they are made right. The plumbing pressure test guide covers the test pressures, the hold times, and the DWV and supply procedures in full.

The test finds the bad joint, but only if you walk it. A gauge that holds tells you the system is tight in total, but it will not point you at the one press fitting nobody pressed, the one solvent weld that is barely weeping, or the one crimp ring that sat crooked. Eyes on every joint while the system is pressurized is how you find the miss before the ceiling below does.

One blunt caution carries across every joining method on plastic: test with water, not compressed air, unless the manufacturer and the code specifically allow air and you have taken the precautions. Water stores almost no energy and a failure weeps. Air stores a great deal, and a plastic joint that lets go under air does not weep, it shatters and throws pieces. Many plastic pipe makers prohibit pneumatic testing of their pipe for exactly that reason.

Code, listing, and approval for the material and use

The joining method has to be approved for the material and the use, and that approval is not a formality. Every pipe, fitting, and joining system on a potable water line has to be listed, and the wetted materials certified to the health-effects standard so they do not leach anything harmful, commonly NSF/ANSI 61, with the lead content held to the lead-free limits under NSF/ANSI 372. The fitting and the joining system have to match the pipe: a PEX-a expansion fitting is not a PEX-b crimp fitting, a CPVC cement is not a PVC cement, and a press fitting is rated for the tube and the service it was listed for.

The fitting and method standards run alongside the pipe standards: ASTM B88 for copper tube, ASTM F1807, F2098, F1960, and F2159 for the PEX joining systems, ASTM F493 and F656 for CPVC cement and primer, ASTM D2564 for PVC cement, ASTM F2620 and F1290 for polyethylene fusion, and AWWA C606 for grooved joints. Pressure piping in mechanical and process work also falls under the ASME B31 family by service, and medical gas under NFPA 99. Mixing systems that were never listed to work together is a way to fail a joint or an inspection.

The last word belongs to the AHJ. The model codes, the IPC and the UPC, set the baseline for which methods are approved and where, but jurisdictions adopt different editions and write local amendments, and some restrict a given joint, like a concealed push-fit, in certain locations. Confirm the adopted edition, the local amendments, and the AHJ before you commit a method on the spec. On commercial and data center work the project specification and the manufacturer's instructions are commonly stricter than the code, and where they are, they govern.

What to document

Record how the system was joined, because the joint is what a future repair has to match and the joint is what the inspection turned on. The record answers the question years out when a line weeps in a wall and nobody remembers whether the hot main was soldered or pressed, or which PEX system takes which fitting.

Capture the joining method by material and zone, the solder type or the cement used, the press tool and jaw with its calibration where the system tracks it, the cure time allowed before any pressure went on a solvent weld, the hot work permit and fire watch if a torch was used, and the pressure test result that proved it tight. If a transition or a dielectric fitting was installed, note where, because that is the spot the next person must not get wrong.

Common mistakes

• Soldering a wet, dirty, or unfluxed joint, so the solder never wicks in and the cold joint weeps in a week.
• Overheating a solder joint and burning the flux off before the solder flows.
• Solvent welding with no primer where the system needs it, or too little or too much cement.
• Pressurizing a green solvent weld before the cement has cured for the size and temperature.
• Using PVC cement on a CPVC joint, or the wrong cement for the plastic.
• Leaving a press fitting unpressed and not walking every joint to catch it at the test.
• Pressing over a burred tube end and nicking the O-ring.
• Over or under tightening a threaded joint, splitting a plastic thread or leaving a spiral leak path.
• Brazing a refrigeration or medical gas line with no nitrogen purge, scaling the inside of the tube.
• Using a push-fit joint concealed where the AHJ requires it to stay accessible.
• Landing copper straight onto steel with no dielectric fitting and starting a galvanic cell.
• Covering or backfilling a joint before the witnessed pressure test proves it tight.

Field checklist

Standards and references

The framework is the adopted plumbing code, the IPC published by the ICC or the UPC published by IAPMO, which sets the approved joining methods, where each is allowed, the dielectric requirement at dissimilar metals, and the pressure test. The code is adopted by edition with local amendments, so the AHJ and the adopted edition control over any rule of thumb here.

Drinking water contact is governed by NSF/ANSI 61 for health effects, with lead content held to NSF/ANSI 372 and the lead-free limits of the Safe Drinking Water Act, the 0.2 percent cap on solder and flux and the 0.25 percent weighted average on wetted surfaces. The joining systems carry their own ASTM and AWWA standards: ASTM D2855 for the solvent-weld procedure, F493 and F656 for CPVC cement and primer, D2564 for PVC cement, F1807, F2098, F1960, and F2159 for the PEX systems, F2620 and F1290 for polyethylene fusion, and AWWA C606 for grooved joints, with copper joining guidance from the Copper Development Association. Pressure piping by service falls under the ASME B31 family, and medical gas under NFPA 99 with certified installers and verifiers. Fire sprinkler joining follows NFPA 13.

Cite the standard that controls the point and confirm the specifics against the current edition. The manufacturer's instructions and the project specification, on cure times, on press tooling, on fusion procedure, and on whether a method is allowed in a location, can be stricter than the code, and where they are, they govern.

Units and terms

The same joint goes by different names across a drawing set, a spec, and a supply house, so a few terms keep the conversation straight. Sweating and soldering are the same copper joint. Pressing and crimping copper with a press tool is a different thing from crimping a ring onto PEX, even though the word crimp gets used for both. Solvent welding, solvent cementing, and gluing all name the same plastic joint, and gluing is the least accurate of the three because nothing is glued.

Temperatures here are in Fahrenheit, with brazing filler above about 840 F and a fusion heater plate near 400 to 450 F. Pipe thread is the tapered NPT unless a drawing calls out a straight thread. Lead-free limits are given as a percent by weight, 0.2 percent on solder and flux and a 0.25 percent weighted average on the wetted surfaces of fittings and fixtures.

Soldering / sweating

Joining copper by drawing lead-free solder into a clean, fluxed, heated joint by capillary action

Brazing

Joining copper with a filler melting above about 840 F, stronger than solder, with a nitrogen purge on refrigeration and medical gas

Press fitting

A fitting with an O-ring that a powered tool crimps onto the tube, no flame, with a witness mark for full insertion

Solvent weld

Chemically fusing PVC, CPVC, or ABS with primer and the cement listed for that plastic, not gluing

NPT

National pipe thread, the tapered thread sealed with PTFE tape or pipe dope, not by the threads alone

Grooved coupling

A gasketed, segmented housing over a rolled or cut groove, the fast mechanical joint for large steel under AWWA C606

Cold expansion

The PEX-a joining method under ASTM F1960, the tube is stretched over the fitting and shrinks to grip it

Heat fusion

Welding HDPE pipe into one continuous line with a heater plate or an electrofusion coil

Dielectric fitting

An insulating union or nipple that stops galvanic corrosion where copper meets steel

Related tools

Calculators and readiness checks for this work

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