Have you ever wondered how to slope a trap arm (aka the fixture drain)?
The trap arm is the short piece of pipe between the plumbing trap and the vent.
It’s a valid question…
After all, the plumbing code wants horizontal drains sloped at ¼” per foot…
But how does code expect you to slope a pipe that’s a mere few inches long?
Brute force isn’t going to move a pipe that short.
So what do you do?
The answer is easier than you think…
Let’s first clear up a common misconception:
Most folks think a sanitary tee makes a 90-degree angle…
People also believe quarter bends make 90-degree angles.
But do these fittings create a true 90 degree angle?
No, those fittings ARE NOT 90-degrees.
The angle they create is found in ASTM D3311.
According to this standard, all 90° fittings must have “built-in pitch” in the sockets.
And here’s the beauty of it all…
This built-in pitch provides horizontal pipes with ¼” per foot slope.
That means a sanitary tee is actually 91.2 degrees…
And a quarter bend is actually 91.2 degrees.
Pretty cool, right?
Keep in mind, DWV fittings that don’t make a 90-degree pattern don’t have built-in pitch.
For example, an eighth-bend (45) does not have built in pitch, it makes a true 45 degree angle.
Also, this pitch does not occur in vent fittings…
The vent 90 (and the vent tee) make true 90-degree angles.
So what’s the secret to sloping a short trap arm?
Install your vertical pipe “plumb” and that short trap arm will have proper slope thanks to the fitting’s built-in pitch.
See, it’s easier than you thought!
Here’s another thing that’ll make your life easier…
It’s our Bathroom Blueprint Training.
This training is responsible for giving everyday DIYers the ability to do their own plumbing (and save $1000’s in labor costs too).
You’ll find plumbing plans, diagrams, and a handful of training videos for a heck of a reasonable price (that price will soon be increasing).