Select Page

# Question on pressure

Home Forums Public Forums General Plumbing Question on pressure

• Author
Posts
• #275735
Bill

I’m taking some classes on plumbing and I am trying to figure pressure out. I studied about the Hazen-Williams coefficient but am having a hard time visualizing it in my head.

This week, I am trying to figure fire flows from open ended hydrants with different pressure ratings.
Can anyone help me with some short cuts on the math or help me with just how to remember all this stuff.

• #292799
NickHydro
Participant

Rmember thatits all on thenet.

• #292800
MOE
Participant

et, your way behind times, the Hazen-Williams method of determining flow curves on liquids at various velocity and motive forces have ceased to be exceptable criteria for the evaluation of
hydraulic behavior in closed conduits.
By the extrapolation of known criteria lists of
A-X3 and A-X4, it is possible to do a quantitative parabolic representation of the volume vs time quotient with the resultant volume being expressed in Liters per sec Diameter squared.
MOE

• #292801
et
Participant

Not what I’ve been told. Hazen-williams is still used in many models as well as Darcy-Weisbach. It’s just hard to do the figuring with this stuff.
I can see if you have a fire hydrant on a 6 inch line and say it has 80 psi, the hydrant gets hit by a car and breaks off. As a plumber, all I should care about is that a lot of water is going to come out of the ground and it needs to be shut off before I fix it. Why do I need to know how to figure out how much water is wasted? I ask my instructor and it’s just part of the classwork to him, needed for my license test. Maybe engineering is easier….

• #292802
MOE
Participant

et: I realize the quandry that you find yourself in. Stuck in a situation where your teacher or instructor stands between you and your license or diploma. Learning quantum mechanics and quadradic equations in order to passify a written test is in it’s self a test..of long suffering.
There is only person alive in the entire known universe that has all the formulae for finding out anything about anything and everything filed
away in his quite considerable memory.
There is a wizard known to those who seek him as “Sylvan” who lives atop a forboding mountain top in the Kingdom of Westchester. Many attempt the journey up the mountain to see the Wizard, some never return, but most quit from the hardships found on the trail of knowledge. Many
quit before setting foot on the trail and complain loudly about the effort that will be required to win the prize.
My advice for those determined to meet the wizard in his lofty mountaintop cave is to steel yourself for a grueling odyssy. The darkness and eerie surrondings become more and more telling as you pick your way along the perilous trial.
I time you will reach the most difficult part of your ascent.You will come to spot at the end of the narrow path on the edge of cliff, there you will find a tattered and worn rope ladder that goes straight up the craggy face of the sheer mountain side. It is always raining and the wind howling in this spot and as you look up the thread bare rope, it disappears in the swirling mists that alway obscure sight of your objective.
Hold fast to the rope and don’t look down, repeat to yourself what it is that you have come for and take courage in the fact that you are nearing your goal with each rung of the worn, wet and slippery rope ladder. As you eventually haul your exhaused wet form to the landing at the end of the ladder, you will see a sign with an arrow pointing the way to “The Wizard”.
There at the entrance to the Wizards cave is huge wooden door of massive beams bound with Cast Iron plates and hung on great Wrot Copper hinges.
Bang three times on the door with the large ball peen hammer tied to the door lock with candle wicking and state the reason that you seek and audience with the wizard as loudly as possibly can, and say..”MOE SENT ME”.
When he asks how you will pay, Cash, Check or Plastic? Go with the Cash option, and your sure to get in. The wizard will be happy to share with you all his stored forulae and other means and methods used to arrive at the correct answer to your queery.
you will of course to bring with you those fact and figures that are required to be used in the use of the appropriate formula.
For example, you will need the total developed length of the 6″ piping to be used for the test. What astm number is the pipe..how many fittings and what type were used and where were they placed in fabricating the 6″ line in question and were they AWWA aproved..What type and bury were the fire hydrants (Kennedy, American Darling, Watrous, etc)
Will you have pumping or supply capacity to maintain the water test pressure during actual testing proceedure? and stuff like that.
Be sure to tell the Wizard that things just ain’t the same around here since they took him away.
MOE

• #292803
et
Participant

Moe, was you in a confined space just a little too long today with just a touch of sewer gas or low oxygen levels? What the hell was that about!

• #292804
MOE
Participant

et: At different phases of the moon, I have a particular need to stay on my medications.
MOE