Plumbing Exam Solution

Pythagorean Theorem

For any right triangle, the square of the hypotenuse is equal to the sum of the squares of the other sides.

Run for the door! Cover your ears – there is that “C” word.

Does this bring back school day memories?


C word

Hypotenuse made simple

Forget about Pythagorean Theorem, it’s just simple math.

Calculating C, travel, or hypotenuse is basic math for anybody involved in the building trades.

I have used this formula for sheet metal fabrication. Welders need it as well as Plumbers, Mechanical, and GC Contractors.

Struggling with Plumbing Isometric, Vents and Drains?

Check out NCCTI’s Plumbing Tutorial –

Plumbing Contractor Exam Math 101

Plumbing Math made Simple


Can you tell me why people flunk the Plumbing Contractor Exam by one or two questions?

Plumbing Offset Language

Plumbing Offset Language

Here is a Plumbing Exam Question that pops up from time to time. Answering such questions correctly just might push you over the top.

A sewer is being installed with a 1/8 inch fall for a distance of 100 feet. How much lower will the discharge end over the inlet end?


Here comes that C word!

Let’s covert 1/8 inch to a decimal equivalent  –   1 ÷ 8 = 0.125

0.125 x 100 = 12.5 feet lower or for every 8 – 1/8s  the pipe drops a foot so 100 divided by 8 = 12.5 feet

Pretty simple, How about – if the set = 12.5 and the run = 100, what would the travel equal?

Let’s word this question differently. A sewer installed with a 1/8 inch per foot slope and falls 12.5 feet. How long is the sewer pipe?

Calculate the length of pipe

C – Travel – Hypotenuse

Please send me your answers. I will post the solution soon.

Answer to Free Plumbing Exam Question

Answer to Free Plumbing Exam Question

The column of water is 50 foot high.

50’ x .434 = 21.7 psi

On the Plumbing exam, this question might get turned around.


For example;

What is the height of a container that 65 psi is measured at the bottom of the container?

Head = psi x 2.3
Head = 65 x 2.3
Head = 149.5 feet


Need more help to prepare for the North Carolina Plumbing Contractor Exam?

No problem, just sign up for a Plumbing Contractor Practice Exam or order NCCTI’s Plumbing Tutorial.

Free Plumbing Exam Question

Free Plumbing Contractor Exam Question

First, let’s define head – amount of water pressure in a column between points at different elevations that is expressed in feet.

Why do we care about pressure head? Because it’s on the exam, savvy?

Understanding Water Pressure

Let’s take a look at the following example:

Plumbing Head Description

Cubic feet conversion to psi

Now I will break it down further

psi head calculation

0.434 psi = 1 foot and 2.31 feet = 1.0 psi

What is the pressure loss for a 3/8”water supply pipe that travels 50’ vertically?

I look forward to your comments and will post the answer soon.

Plumbing Code and Pipe Sizes

Chapter 2 in the 2009 NC Plumbing code is very important to passing the Plumbing Contractor Exam. Let’s look at Section 305.5 on page 14. When plumbing pipe passes through a foundation wall, the pipe requires to be sleeved. “The sleeve shall be two pipe sizes greater than the pipe passing through the wall.” If a three inch pipe is passing through a foundation wall, what size will the sleeve be? Now look at pg. 9, PIPE SIZES definition. Two pipe sizes would equal a 4 inch pipe. That doesn’t make sense, who has ever seen a 3 1/2 inch pipe. Have you ever seen a 2 1/2 inch pipe? I suppose that you could special order one. Here is the point (especially for seasoned plumbers), the Plumbing Contractor Exam is not necessarily about real life plumbing. The day to day plumbing that a plumber executes may not apply to the exam. Its all about code comprehension and a fast and steady look-up. As far as the Plumbing Contractor Exam, mastery of the reference books trumps plumbing experience. I think experienced Plumbers might be at a disadvantage come test time. Sign up for any of NCCTI’s Plumbing Practice Exams to learn code and improve look-up skills.

Test Your Plumbing Isometrics – Solution

Please refer to “Test Your Plumbing Isometrics” Blog (July 1)

Do to request for more Plumbing Isometric Blogs, here is the solution to the “Test Your Plumbing Isometrics” blog I posted a while back. For this drawing, all private wc’s flush greater than 1.6 gpf. You will notice that there are three bathroom groups for this residence. First, define bathroom group – pg.6 NC 2009 Plumbing code. Then look at pg. 59, Table 709.1., each Bathroom group counts for 6 dfus. Also, read footnote f -for fixtures added to a bathroom group, add the dfu value of the fixture. This is important because the upper right hand Bathroom group has an extra tub that must be added to the 6 dfus – 6 + 2 = 8 dfus. If the drawing had 1.6 gpf wcs, then footnote i states that you add 2 dfu for each additional Bathroom group. This would change the total dfu load. Because our water closets have a flushing capacity greater than 1.6 gpf, each Bathroom group counts as 6 dfus plus the extra Bath Tub must be added.To size the drain, the total dfu load must be added up and then look at footnote c for Table 710.1(1). The whole point of this lesson is to pay attention to the footnotes for all Tables.