Saturday, May 16, 2009

Modern Plumbing - Braided Hose Supply Lines

Yes, this is a health issue.
  • It's extremely a mental issue. Think about the problem 20 years ago, and how crazy it made people.
  • The need to supply water to a sink or toilet, reliably, is a health issue too.


Did you ever do any domestic plumbing work, 10 or 20 years ago? Did you ever have to install or upgrade a sink or toilet? If so, I'm sure that you remember installing water supply lines that used "flex" tubing with compression fittings.

Professional plumbers will disagree with me, I'm sure, just as I'm sure that Do It Yourself handymen will agree with me. An install of a water supply line, that used flex tubing with a compression fitting, was an extreme mental exercise.

The object of a water supply line is to transport water from the supply - generally a pipe sticking out of the wall or floor - to a plumbing fixture - generally a sink or toilet. The water being transported is under pressure. If any holes - however miniscule - are present in the supply line, the water will leak out, onto the floor. This is not an acceptable situation.

So, we had the flex tubing. Flex tubing can, and must, be bent when installed.
  • The two fittings - supply and fixture - are never in a straight line with each other. Bending the tubing would compensate for the fittings being out of alignment.
  • Bending the flex tubing, which could be bent but would resist bending, created a "spring" action. This would force the ends of the flex tubing against the fittings at either end, a key ingredient in making a fitting watertight.


Flex tubing can be bent, but not too much. If you bend a piece of flex tubing too much, you'll get 2 bad results.
  • The spring action will break, and you'll have a piece of scrap pipe, useless because it won't force itself against the fittings. The fitting will leak, slowly. This is bad.
  • The walls of the tubing will be weakened, and eventually water will find a way through the walls. You'll get an open break, under pressure. This is very bad.


On the other hand, if you do not bend a piece of flex tubing enough, you'll get two results.
  • The tubing won't fit into place, it will be too long.
  • The fitting won't have spring action, and it will leak.
Again, 2 bad results.

Sizing the length of the tubing was an essential process. The tubing had to be long enough - by tolerance of maybe 1/16" - to fit into the fittings, forced against each fitting end. As sold in stores, you could get maybe half a dozen lengths to choose from. Buying tubing correctly sized to 1/16" tolerances wasn't a possibility, so you would have to buy a large size, and cut the tubing to the correct length. The necessity of cutting the tubing created several possible problems.
  • Since the tubing had to be cut, it had to be installed without a flared end. To compensate for this, you have a compression fitting. This uses a compression washer, and a compression nut, which you tighten against the fitting, to make everything water tight.
  • The tubing has to be cut with a square end, to allow the end of the pipe to fit squarely against the fittings.
  • The tubing has to be cut carefully, so it's not squashed. It has to be exactly round in cross section, or it won't fit inside the fittings, which are precisely round and precisely have an inner diameter equal to the outer diameter of the tubing. Again, this makes the fitting watertight.


When you tighten a compression nut against a fitting, you are only malforming the compression washer, so it forces itself into the fitting, and makes it watertight. You are not contributing to the tightness of the tubing, inside the fittings. The tightness of the tubing is only created by the spring action of the tubing being bent into place.

You have to tighten the compression nut hard enough to malform the washer enough, but not too much. If you tighten the nut, and malform the washer too much, you'll get a broken or flattened washer, or possibly a flattened piece of tubing end. Any of these will detract from the watertightness of the fitting, again a possibility for a leak.

And neither the tubing, nor the compression washers, were reliably reusable. Once you tightened the washer into the fitting, it would somewhat weld itself to the tubing. If you were to remove the tubing to re install it, maybe because a fitting was leaking, you would take off the washer, throw it away, and install another.

Do you see how precisely everything fits together, to make the fitting watertight? This is a serious engineering exercise. A hole so small, that you can't see, will let water seep, and eventually a fitting will burst. Very bad.

Now, we have truly flexible hose, inside a braided armour shell.
  • The flexible hose is like a plain old garden hose, it hangs loosely when it's installed.
  • You buy a length long enough to easily reach between the two fittings, screw the two ends onto the two fittings, the excess length hangs in a loose loop (again, like a garden hose), and you're done.
  • Since you don't have to cut the hose, it comes preassembled with nipple ends, plastic or soft metal.
  • The ends are watertight, so no compression fitting has to be added.
I can't believe it's that simple, but there you are. And that's why this is a mental health issue.

1 comment:

golfer said...

I am a licensed mfd home installer, when you have a double or triple wide with water on both "floors" you need to connect the "marriage line" hot and cold between floors.

One nearby state says it must be the copper braided (which you're right doesn't give much), the state I live and work in says strictly the "flex" black braided hot water connectors Low*s sells.

What is your take?

The black ones are certainly my choice overall, not as much flex as the copper, BUT extremely durable and you can almost make it a pretzel if its long enough (which you can't do with the copper).