Talk:Hazen–Williams equation

So much for the SI units... 62.242.0.66 09:35, 24 April 2006 (UTC)

Formula

HELLO EVERYBODY, this is an important formula, for water in a pipe. I object because this article does not mention the LENGTH of the pipe. There should be variable "L" added to the formula, if the pipe is 231 feet long, then L=231. Most people will want to know the pressure drop for the whole pipe, not just "per foot". I think this formula is only for "Unit length" of pipe, i.e. pressure drop for 1 foot. But I didn't do the math, can't somebody fix this up? As to SI vs English units, sure make a separate formula thats metric, but for the whole continental USA there's plenty of gallons per minute, and feet of pipe, etc. —Preceding unsigned comment added by 208.32.186.35 (talk) 20:51, 12 October 2007 (UTC)

There is no L in this formula, and there's not supposed to be one... this is an established formula and it doesn't need to be changed simply because you think it should be. The Hazen-Williams formula determines pressure loss due to friction PER FOOT (which is noted in the article)... The answer is measured in psi/ft technically. It gets bastardized (especially in the fire protection industry) and dumbed down to simply "psi" even tho that is technically incorrect and the units are, as I said, technically psi/ft. You then, obviously, multiply the answer by the length of the pipe in feet to attain the total pressure loss due to friction in a given length of pipe measured in psi. Again, the Hazen-Williams formula is not meant to give you the total pressure loss due to friction in a given length of pipe... it is meant to give you the total pressure loss due to friction PER FOOT in any pipe.76.116.14.38 (talk) 01:03, 20 February 2008 (UTC)

Can you give me the reference? Because when I looked up Hydraulic Design Handbook by Larry W. Mays, I can't find anything related to psi/ft etc.Isa982 (talk) 23:34, 26 November 2008 (UTC)

I don't know about that specific book, but I have the 2007 version of NFPA 13: Standard for the Installation of Sprinkler Systems opened in front of me, and on page 13-213, 22.4.2.1, it clearly reads:

22.4.2.1 Friction Loss Formula
22.4.2.1.1 Pipe friction losses shall be determined on the basis of the Hazen-Williams formula, as follows:

p=4.52Q^1.85/(C)^1.85(d)^4.87

where:
p = frictional resistance in psi per foot of pipe
Q = flow in gpm
C = friction loss coefficient
d = actual internal diameter of pipe in inches

Hello everyone, I just changed the formula again to remove the "L" variable, as it is NOT part of the equation. I don't understand why everyone is so eager to change an already established equation based on their personal opinion. If you can cite a reference that says the actual Hazen-Williams Equation for calculating pressure drop includes an L variable, then cite it. Here are some references showing that it does NOT include an L variable, and in fact, P_d is psi/ft, kPa/m, or bar/m, depending on your locality. In one of the above links (vccs.edu), they include an L, but notice how it is only multiplied after the base equation is performed, basically P_d * L... without the L, it is pressure/unit! Even the PDF that is directly referenced (Ref 5 on the article) on the SI equation shows that there is NO L in the equation there. 208.214.101.206 (talk) 21:41, 27 February 2013 (UTC)

Only in America?

The article lead implies that this equation is not used outside America. If that is true then it's somewhat bizarre and worth some mention (and a citation). If it's not true, then the word "America" is misleading and needs to be removed. Anyone got an answer? • TheBendster (talk) 2 May 2008, 17:56 (UTC)

OK, I removed it. • TheBendster (talk) 6 May 2008, 11:31 (UTC)

d is in mm

The way it is custom to use in Israel is the following:

hf(m)=1.131*10^12((Q(m^3/hr)/c)^1.852)(d(mm)^-4.87)L(km)

Where Q is the flow rate, d is the pipe's diamater and L is the pipe's length, in the article it was written that d is in meters. —Preceding unsigned comment added by 84.229.239.234 (talk) 18:03, 8 July 2010 (UTC)

Fixed error in formula

The original formula P(psi) = 10.44 * Q^1.85/ C^1.85 * d^4.84 is incorrect, as this provides pressure in *feet of water*, and not psi. For psi the correct formula is P(psi) = 4.52 Q^1.85 / C^1.85*d^4.84. The difference in this constant is the conversion from psi to feet of water (2.307). Luis H Palacios (talk) 20:38, 19 April 2013 (UTC)

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