: Hello, I hope someone here can help.
: I am a second year UA apprentice in NJ and one of my mechanics gave me several code questions and 3 math ones, he loves busting my Onions.
: Can anyone please give me the answers to the following as I have been looking all over and cannot find these answers.
: 1-The strainer inlet for a 3" leader line is?
: A- 7" B- 9" C- 11 " D - 14"
: 2- A 3" pipe full flow of 180 GPM has a velocty of ?
: 3- A pump is pumping 50 GPM with an efficency of 75% what is the horse power of this pump?
: Would this really be plumbing questions or is just busting my chops?
: Thank you so much, Arthur
Wow, your Journeyman must think very highly of you to ask these questions as these are normally given on tests to 4th and 5th year folks.
Your very fortunate to have a mechanic who wants to teach you the why not just how.
The first question is a humdinger of a question and I had to read it several times before it hit me it is a code question not just simple math.
Anyone can find the area of cylinder (pipe) BUT the mechanic said "leader" thus things change
The very first question a decent mechanic would ask is what type of leader drain is this for?
Promenade deck or roof / area drain used for weather protection only?
If it is strictly used for a "leader" we can probably assume it is for a weather protection and on a roof or possibly a building set back.
Either way this question is basic "code" lets start off with the simple stuff 1st.
Leader 3" diameter Would be as follows Pi x radius squared correct? Equals 7.06 inches?
If you agree Arthur we move on to step two.
Now being a future mechanic you know it can't be that simple so you think and say
"hey wait a minute suppose this is wide open pipe stuff can fall in huh?"
So we need some type of protection, so we think DOME, BUT domes do get debris build up at the base and thus are rendered UNLESS we figure in some type of safety factor say 11/2 times the opening (this is basic to most codes)
So you look up your state/city code to double check me and then work the math out which comes to
7.06 X 1.5 (safety factoring) equal 10.59 which rounds off to C 11 Sq. inches TA DUMMM
Now lets go one step more and say why cant it be a promenade deck / area traffic top roof?
Using the basic code we find a flat grate requires TWO times the actual drainage area
So lets review 3 "dia leader times PI equals 7.06 " times 2 would be 14.12 Square inches
THUS making the D- 14 ILLEGAL as it is undersized, bigger is better (and legal)
So the only possible answer in this case is C. wow we are good huh ?
Rather then fill this space up with more math which bore the mechanics on here with ILL give you the other two answers and you can contact me by E mail if you want to know how I arrived at these answers.
A 3" pipe full flow of 180 GPM has a velocity of 8.17 FPS (Not taking friction losses into consideration)
3- A pump is pumping 50 GPM with an efficiency of 75% what is the horse power of this pump?
HP = 2.75 Double check your plumbers math book it should be in there or again E mail me
Q- Would this really be plumbing questions or is just busting my chops?
A- He is NOT busting chops he is one of the much better mechanics willing to take the time to do his job TRAIN apprentices. U/A plumbers are without a doubt the best trained in the industry STICK WITH IT. Plumbing / Fire suppression / heating are amazing professions if taken seriously.
My apprenticeship consisted of 10,000 hours training plus 744 hours class room codes and theory. PLUS going extra time (classes) to be slightly ahead of the herd
As U/A apprentice I leaned welding gas and electric and fusion to pass certifications, brazing (for medical gasses certification), lead wiping, lead burning, caulking, soldering, working with Pyrex making our own beads, blue print drawing and reading, fabricating lead pans
These types of questions appeared on my apprentice tests in the 1970s and later on several of the master plumber tests I had taken and passed.
You have a great U/A Instructor in NJ Steve Paul who instructs mathematics for the UA apprenticeship.
He and I attended the same classes as apprentices but he was one year ahead of me, he is just amazing in heating and figuring out this plumbing numbers game.
He is the plumber, great plumbers go to for advice
If you see him please send him my best.
Here is an offer ILL give you. When you get your class A. Journeyman card I will start you off at $50 per hr in the envelope PLUS benefits and profit sharing. I will send you a contract for 2 years with a yearly pay increase of up to 10% of your hourly rate.
When you finish and pass your 4th U/A year apprenticeship ILL start you off at $30 per hr
Fair enough incentive for you to finish?