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Pete the Plumber has an apology this time around for any plumbers visiting In The Pipe. This post deals with a topic which will surely bore you to tears, so maybe you wanna skip this one and check back in
another month. For the non-plumbers and the ‘basically curious’, the author believes this post will prove worth your reading time.
The plumbers of today would have a harder time making ‘things’ work if PTFE (Teflon™) hadn’t been invented. But it was. And, plumbers love the stuff, whether in the form of ribbon, paste, string-packing, or flat, rigid shapes (faucet washers; large-hole, thin, friction washers (for valve spouts and shower heads); and, many internal valve components/cartridges utilize it. Since the application of ribbon-tape- to-male-threads is now so basic to the plumbing trade, and since so many laymen botch the job of applying it, the author felt he should attempt to ‘put that topic to bed’, for good. With this post he’s going to try and send you away with probably the most basic trick in the plumber’s bag. It will be
‘a-bit-of-a-hike’ for the person not wanting to know more than some basic facts about what no longer exists: Teflon™ tape. So, the first push of this article will merely be a background focus. But for those with the stamina, on the second push I’ll tell you how to be more successful using “Teflon™” Tape, That Isn’t.
The Tape That Isn’t, And Why Plumber’s Love It So Much
Isn’t? What’s this “isn’t”? Well, that’s a fun question to answer, if you’ll grant me the privilege. The author admits he’s an antique and/but his recall predates “Teflon™” tape. The now ubiquitous, ribbon-form, white (originally) pipe thread sealant, like many other great inventions, eventuated from a failed lab experiment. Prior to the early 1960’s, civilian plumbers had only oil-based pastes, and fibers (flax and hemp) to seal threaded piping systems.
When you hear the word plumbing, what first comes to mind? Besides that. For many it’s pipes and water. Back in ’38, plumbers had fewer piping choices than they have today. For waste systems, inside buildings, then, it was ‘bell and spigot’ cast iron joined by oakum and molten lead. For water systems it was malleable iron and steel and brass. (Lead, for supply, in-building, by this time was nearly extinct.) The iron/steel and brass were/are joined by the utilization of male and female threads. Today in the residential sector there are additional fresh water piping choices: schedules M, L and K copper, CPVC, PEX, Hypertherm 2399, and who knows what’s next. These “modern” choices utilize flame; solvents and cements; insert fittings/compression rings; and, push fittings. A relative late comer is the Press System which utilizes copper, steel and PEX piping and proprietary fittings joined by extreme pressure via specialized, electric tools. These later choices are thread-less methods. So, basically, plumbers employ the ribbon tape that isn’t on Threads. (But not only for fuel gas and pressurized water, the stuff is indispensable for threads found in gravity DWV systems also.) Downstream the author gives the reader a little insight on threads, an invention of antiquity (3000 + yrs. ago?) one born with plumbing (irrigation) in mind.
Now Why It Isn’t
A very smart young man named Roy J. Plunkett (from simple Ohio beginnings), graduated in 1927 from high school and had gone off to Manchester College, Indiana, showing real promise in the study of chemistry, earning his B.A. Then it was off to Ohio State University for his M.A. and PhD. There he met another very smart young man, Paul Flory (who later won the Nobel for chemistry). They were roommates at OSU. I can just imagine the dinner prep/KP discussions those two had. Both reached pinnacles in the chemistry world of polymers (rubbers and ‘plastics’) (Tom Thumb moments).
The epochal chemistry moment we’re concerned with, the discovery of PTFE occurred in 1938 when we find Plunkett in the employ of the newly minted DuPont Company. In short, what Roy J. Plunkett concocted was a pasty white powder, and possibly the world’s slipperiest material (polytetrafluoroethylene.) Like many great inventions it was discovered before there was a market for it. What Plunkett had accidentally done was to polymerize tetrafluoroethylene (gas) into polytetrafluoroethylene. Between 1938 (“April 6, 1938”) and 1945, when it was patented, there was a lot of cooking-pushing-poking-stretching. It’s official, copyrighted , commercial name, now held by Chemours Co., is Teflon™.
PTFE was first put to work in munitions fuses and in a degree of liquid form, as a hi-tech R & D sealant. Its first and biggest customer was our ‘Dear Uncle’. He needed this miracle at work for his fledging aerospace (Defense in general) (no-pun), industry. As an almost paste form it was used to seal rocket sections. (How many remember the other “Ride Sally, Ride”?) That nightmare was a neoprene o-ring failure between rocket sections. It’s ironic that PTFE is as deeply entwined within the Plumbing Industry as Buna-N neoprene.
Anyway, you’ll notice (this is a test) that the miracle material PTFE in tape form is not advertised as Teflon™ Tape. All you will see mentioned on the spool sides is PTFE. There is no “Teflon™” tape. That name now belongs to Chemours, (a related company) and they do not make Teflon™ tape. (And they want everyone to know this and desist from identifying PTFE, in any form, as Teflon™. (I think Du Pont once did sell the tape and called it Teflon™.) They’ll sell you their powders to manufacture it yourself if you go through the legal hoops. My memory on this subject of tape form goes back to the late fifties and early sixties. I “think” I remember seeing the words Teflon™ and DuPont, spelled out, on spools of the stuff but according to the literature that is not conclusive. That “imaginary?” spool, I think I remember, was designed not to be opened; it was shaped like a tape measure, with a flat bottom, and “tape” dispensed out of a slot. In this case there was a built-in sharp blade that cleanly cut the exceptionally thick tape in two, by squeezing the plastic spool. The author has worked in several labs, government and private, which would have used top quality but I can’t recall in which camp it was encountered.
The tape is, as you well know, sold in several widths (and colors.) The most common for plumber/homeowner is the ½-in. width. I’ll use this width for threads (it has other uses, too) up to 1½-in. pipe size even though you see recommendations in the literature for wider tapes here. The number of wraps to make is determined by the length of threads and the tolerances of the parts to be joined. For 2-in. pipe and above it’s more convenient and quicker to use ¾- or 1.0-in. wide tape. The author has read recommendations by the manufacturers and other plumbers for distinct tape widths for distinct pipe diameters. The author can successfully fit 2-in. pipe with ½- in. wide tape. It’s the coverage depth (thickness) that is the concern here. It does take longer to wrap the ½-in. for the larger pipe sizes but this does not mean you must adhere to these printed width-to-diameter tables. The ultimate arbiter is NO LEAKS! Also, the medium that’s going to be flowing in the new system figures into how I apply the stuff, which I will tell you about downstream.
I have no figures to substantiate my hunch, but I think the pipe trades, or for a better choice: the sealing of threads (many kinds, many industries/occupations), constitutes a major activity that TPFE manufacturers satisfy. (Though the author once applied (with many, tiny, bronze, flat-head screws), long, half-in. wide strips of PTFE, ¼-in. thick, on the bottom of a wooden two-man kayak, so as to paddle rocky riffles.) The boat was named by a friend, its builder (not PtP): Agape. (My friend was a highly religious fellow.) Never knew for sure though, whether it was the boat’s name or all of the PTFE bottom strips, but Agape had a long and exciting career. It was never wrecked. A flood took it away. (But the speed, smoothness and durability with which you rode on boulder and cobble was easily discernible from that of wooden bottoms. I had to be certain it was beached on level ground and tethered, or you could turn around to find it racing back into the water.)
In the author’s first published pedagogy (The Straight Poop, A Plumber’s Tattler) he attempted, in text and through a series of rather amateurish, artistically illustrated hands, to show how to apply ribbon tape to a pipe nipple. I don’t know how much the drawings helped, but The Straight Poop, A Plumber’s Tattler is still viable, and available on the used market.
Threads and Nipples
They can be long, short, from tiny diameter to large. (In my early days in the trade, any pipe, any pipe material, longer than 12” was referred to as a “section” or “stick”.) Up to 12 inches was a nipple. What was common to all steel (no HVAC), and brass ones though were threads. Have you ever given much thought to threads? No, not your fine duds, but the modern day extrapolation of Archimedes’s screw, possibly our earliest example of functioning threads, which he incorporated into a water pump. This Archimedes, another real smart guy, was born in Syracuse, Sicily, in 287 BC. (He died in 212 BC.) The actual invention date of his world benefiting hand carved wooden screw (threads born?) is not known, for sure. Its origins go way back. One British researcher, Stephanie Dalley from the Oriental Institute, Oxford, deciphered cuneiforms of King Sennacherib (Assyrian) describing the casting of brass water screws 350 years before Archimedes’s wooden one. But modern day adaptations can be found in power drills, snowblowers, augers, harvesters, concrete pumps, and the list goes on.
I’ve read Archimedes came to his screw water pump invention just as a major drought was gripping Europe and parts of Asia. A water pump, like Archimedes’s design, using a long screw and long outer tube or pipe, carved with close enough tolerances, lifted canal water much more efficiently than by man and bucket. (He developed his screw after visiting Egypt, where it might already have been in use.) Today when we apply PTFE, both tape and paste, to male (and especially in our case) male iron pipe threads (MIP), it’s done to both take advantage of PFTE’s slipperiness to counteract the friction of threads-in-mesh, allowing good thread purchase (engagement), but also its sealing quality, filling in the gap between non-precision (perfect) mating threads. The author will go into application details downstream for those curious. Paste PTFE is applied to female threads as well, but there are some tweaks here and I’ll cover those in another post, sometime.
When a non-plumber holds a threaded nipple or a “stick” of manufactured steel/malleable pipe in their hands, they could be forgiven for believing that it is perfectly round. But it is not. It is though, expected to be within close approximation. The out-of-roundness varies by manufacturer. The industry standard of acceptance for near-roundness is one percent deviation per diameter of pipe. The author can sometimes pick up a stick and detect one that ‘got by’ Quality Control. The more degree out of round a threaded pipe or nipple is, the more resistance (per friction) is encountered when engaging (threading) on a threaded fitting, or vice-versa. Female threads in fittings that are an unacceptable degree of roundness are no less problematic. This can mean the necessity of employing bigger, heavier (more tiring) pipe wrenches for joinery than ‘should’ be necessary. And it means increased possibility of leaks.
Other Smart Fellows
Did you know that in 1841 a ‘Brit’ by the name of Joseph Whitworth (1771-1852, inventor of a metal lathe) did something that radically altered the pace of mechanical progress (most appreciated by plumbers)? Whitworth was an inventor with ‘noble’ machinist skills. At the time, “machinists” and other craftsmen were making threads that for some personal reason they favored above other possibilities. There was no standardization. The thread may have differed in as many ways as those creating them. Whitworth forever changed this. It was his and the world’s good fortune that the thread he produced on his-invented lathe was eventually adopted by the railroads of the time, and became known as the British Standard Whitworth. He was not modest about his accomplishment either. In his memoirs he had the following to say about his lathe: ….”worth all the other tools in use in any workshop in the world, for finishing, machining brass and iron.” With his invention, at an opportune time, the screw cutting lathe allowed a standard to be defined and maintained. (The patent on Whitworth’s lathe expired in 1812.)
Another smart guy, William Sellers, an American, years behind Whitworth, in 1864, presented a paper to the Franklin Institute in Philadelphia proposing a new thread standard for the United States. He changed Whitworth’s thread angle from 55 to 60 degrees and altered the tip and valley shapes. This thread design eventually became the United States Standard thread. In time it underwent further refinements to father: NC (National Course), NF (National Fine), and in our interest: NPT (National Pipe Taper).
Of the threads on which plumbers mostly apply PTFE ribbon tape, male iron pipe threads (MIP), (which are National Pipe Taper) are undoubtedly coarser and of less precision than thread found in say the automotive and mechanical fields. These ‘plumber’s’ tapered threads (male and female) form a high friction wedge seal, upon meshing (completing engagement). It’s (or was) common to refer to this completed connection as being married. Not all threaded pipe encountered in the market, with so many suppliers, has threads of equal high quality. When making your own, on equipment not properly maintained, sub-standard quality threads happen a lot, which are more prone to leaks. With quality threads (both male pipe and female fitting), some brands can be pre-assembled with mere gloved hands. Some you can barely get two threads in-mesh without use of ever longer and heavier wrenches. This could be the fault of the male OR the female threads, or BOTH. (On your unlucky days it can be both.)
No amount of liquid/paste pipe joint compound, even PTFE versions, applied to male or female threads, or both, affords the same ease of assembly as PTFE ribbon on male, solo, IF the tape is of high quality. Thank you, thank you, thank you Roy J. Plunkett.
Tape Quality And Color
What makes for high quality in PTFE ribbon tape? A number of things but the two foremost are content ratios of PTFE (purity) and thickness. This differs markedly between tape manufacturers. Early in the ‘PTFE-into-tape’ process it was realized that a thickness standard needed to be established.
Uncle Sam, the first and biggest customer, had his requisites: 3.5 mils thick and 99% purity (of PTFE): MIL-T-27730 A. Much of the ‘industry’ (honest ones) adheres to that or a newer specification: A-A-58092 which also requires the 3.5 mil thickness and purity levels but adds a density requirement of 1.2g/cm3.
The author can still remember the day when a Will-Call clerk (John Paul) shoved a roll of yellow ribbon tape at me from across his counter: “For Nat. gas….new Oakland reg.” (Some community inspectors want to also see yellow tape for LPG fuel gas.) Up until then it had just been one color: white. Turns out a gent (Bill Bentley) I believe in England, had come up with a color code for tape used in different applications. Me suspects what happened…I’ll wager: Some skin-flint plumber trying to conserve on an at-the-time quite pricy supply item (PTFE Ribbon Tape) used insufficient amounts on a gas job and dodged inspection, and at some point the system failed and there was fire and or injury or both. (Greed knows no race or borders.) (Sorta like a standard where cities wait for ten wrecks at an intersection before spending the bucks for stop signs.) The author had been using the proper amount of quality (USA) white tape for inspected water, gas, and threaded DWV, for years, without any problems.
The tape became colored to keep plumbers honest and purchasing 3.5 Mil, high-purity, high-density and allowed inspectors to know the plumbers were behaving. (The purple color of PVC primer and the pink of ABS-to-PVC transition cement are other examples where color was added to assure regulations compliance.) A pink color, connoting 3.5 Mil/99% pure, for general use, was the first color experiment the author recalls. This color for ribbon tape could only be given to quality manufacturers making stuff such as A-A-558902. If the offshore outfits had tried pinking their junk stuff I’m sure there would have been grounds for serious trade ramifications. (We have entered a Public Safety realm, here.) Did this guarantee that there’d be no leaks? Answer: No. (That’s a case for workmanship.) But, it improved the odds for fewer failures. Mill-Rose (good stuff) makes a blue tape (Blue Monster) which is in good part a marketing strategy, but not an official requirement for any particular type of piping (until some senior building inspector adds it to his community’s Local Code). But it is even thicker than 3.5 Mil. (4.0). Look on the outside of any quality spool for the thickness figure and Mil spec numbers or hopefully A-A-58092. The cheap stuff has only PTFE noted, with no thickness or content figures; and, there’s next only the country of origin noted.
Two other color standards were popularized: green for oxygen (can’t have any oils involved) and gray for stainless steel piping systems. The gray has microscopic particles of nickel mixed in which functions as an anti-galling (anti-seize) component. Unless you’re plumbing lab/hospital-medical/R&D you need not concern yourself with gray or green. These colors are for the U.S.; other countries have their own color schedules. For instance, in England green is for water.
In the literature I have seen red flags for using ribbon tape on compressed air. On high pressure lines, if too much tape is used the joint can fail (with much dramatic effect) by separating, dangerously. Also, when creating systems, any type, threads can cut tiny slivers of tape and send them down stream. For water it’s not a big deal because good plumbers remove valve cartridges, shower heads, faucet aerators, toilet fill-valve seals and regulator screens prior to charging their systems and the slivers (and other “line trash”) are flushed out. In the case for fuel gas (and compressed air) slivers can easily be ‘blown’ into difficult-to-access, fine-mesh screens in regulation equipment. (I have advice for you on this topic, downstream, in the second push.)
Tit For Tat
Another benefit to the coloring idea was a leveling of the economic playing field. After the market for the original, standard, quality 3.5 Mil white tape had grown to a size to attract fierce competition, certain countries (I won’t mention names) began selling “at first appearance” look-a-like tape with much less thickness, purity, and density, and of course at a much cheaper price as well as quality. Some of these off-shore outfits resorted to pricking the thinner cheap stuff with pricking equipment as it was extruded to “fluff” it up, in order to claim a thicker thickness than it really was. By coloring the quality stuff it differentiated it from the bogus. I am sure there are smaller, independent makers of quality tape, in a number of countries, but because piping systems are so labor intensive and time consuming to break down and re-fit, here’s a good place not to cut corners. PtP has used pink Mill-Rose brand (U.S.) for decades and found it ‘top drawer’, on water, gas, and DWV. I’ve also used their of-late, thicker Blue Monster line too, but still prefer the 3.5 Mil tape for some uses.
HOT TIP: The author does use the thin cheap offshore ½-in wide ribbon tape for ONE application: the fine male threads on 1¼-in. lavatory threaded tail pieces and the same fine male threads on 1½-in. threaded tailpieces, applicable to kitchen sink waste components and bath waste & overflow tailpieces. These threads are so shallow that the thicker quality tapes are too thick. Because of the extreme slipperiness of PTFE you can easily cross-thread these components. If the author has more than just a couple of failed attempts to achieve ‘threads in mesh’ (engagements) with these components, even without suffering thread damage, I remove the tape and use only pipe joint compound in its stead, with customary success. In a future post I’ll get around to telling you my preferences for pipe joint compounds, and why. (See: Installing And Repairing Plumbing Fixtures.)
Well, that’s the end of the ‘beginner’s hike’, the first push. All who want, “It’s to the showers”! But any thru-traveling die-hard masochists are going to love what follows.
Part 2 - Coming soon...stay tuned.
Peter Hemp is a San Francisco East Bay residential plumber and plumbing author and former R & D steam vehicle plumber. His hobbies are ocean kayaking and touring the Left Coast by bicycle.