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It’s an age-old question, one that has kept philosophers, engineers and homeowners awake at night since the dawn of time: Did I tighten that pipe enough or is it going to leak?
Pipes are designed to withstand a huge amount of pressure. For instance, half-inch schedule 40 PVC pipe — like the pipes you might find in your sprinkler system — can withstand 600 pounds per square inch of internal pressure.
That’s an amazing amount of pressure and it might lead you to say, “Balderdash!” (or some other word). If that’s the case, why am I constantly fixing my sprinklers?”
Whenever products are tested and especially when they are brought to market there is a certain amount of, shall we say, “flexibility” in the claims about performance. You’ll notice an asterisk or a footnote, or some other sort of disclaimer after a grand statement and it usually relates to limiting of all sorts of conditions.
In a lab, under optimum conditions (*), the aforementioned pipe can take 600 pounds of pressure before it fails. However, as we all know from watching any World War II submarine movie, the leaks happen at the connections and under less-than-optimum conditions.
So, if you have a length of pipe that is not damaged when it’s installed it’s unlikely that it will develop a leak unless some external force acts to undo your plans.
The weak point is usually the connections. So, we’ll focus today’s lesson on pipe connections.
Threaded pipe connections: If you look at the threads of a bolt under magnification, you would see that the threads are even along the entire blot. When you tighten a nut on a bolt, the materials between the nut and the bolt are pushed together. Pipe threads don’t work that way.
The threads on pipes are tapered, meaning that they start out small and gradually increase in order to draw pipes and fittings together into a tighter and tighter connection. This is why you can hand tighten pipes to a certain point and then you need to use a pipe wrench or some other tool to complexly tighten the pipe threads.
Once again, if you magnified pipe threads you would probably see all sorts of burrs and other imperfections and this is why plumbers and pipefitters use various compounds and materials on these threads before they put them together. These products lubricate the threads and fill gaps to create a seal.
One of the more widely known products is Teflon tape. It’s easy to use, inexpensive, and not as messy at its cousins, Teflon Joint Compound and “Pipe Dope.”
Pipe dope, by the way, has more adhesive qualities and is used for permanent connections like gas lines and household water lines. Teflon — tape or compound — is more commonly used for parts that may be replaced, like sink connections.
Glued connections: PVC (polyvinyl chloride), CPVC (chlorinated polyvinyl chloride), and ABS (forget it — nobody knows how to pronounce it anyway) are types of plastic pipes you might use around your house. PVC is used outdoors, CPVC can be used for indoor plumbing, and ABS is used for sewer or for landscape drainage.
By the way, there is also a Styrene ABS drain pipe but I don’t like it because it’s thin and roots get onto it too easily.
The key to gluing plastic pipes together is to use the compatible adhesives. It also helps to use the compatible primer, if recommended, and to have clean surfaces. Also, it depends on your time frame and confidence. For instance, I use the fastest-setting glues because I’m confident in my pipe layouts, all my pipe lengths, and all my connections.
I also keep extra parts handy so I can correct my screw-ups!
As long as we’re covering plastic, I should mention that most plastic does not like ultraviolet light (UV). A plastic engineer at GE Plastics once explained it like this: UV is to plastic as X-rays are to humans; too much and it won’t work. So, if you have plastic pipes exposed to sunlight, you should paint them from time to time with an appropriate paint.
It’s unlikely that the average reader would need to connect copper but there are a number of newer “quick-connect” fittings available for copper connections as an alternative to soldering with a torch, which should be left to professionals. These can also be used with newer PEX tubing you’ll find in new homes. Most professional plumbers don’t trust these connections yet but I’ve used them and they seem to work as promised.
The final type of connection a homeowner may encounter is the flared fitting. You’ll see this at gas connection to a stove or water heater and these are designed to be used without any glue, tape, compounds.
So … back to the age-old question: When do you know that you’ve tightened a pipe enough so that it won’t leak? Well, just before it breaks, obviously.
Have an “around the house,” construction or real estate question or comment? Send it to Matt Le Vesque at P.O. Box 108, Yucaipa, CA 92399 or czrmatt@yahoo.com and he will consider it for his column.
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