Flow Charts for Big Size Pipes

Saint Goubain PAM's technical center had what I needed, at least for ductile iron pipes, thanks for the help.

Hello,

Instead of relying on charts and flow Nomographs (which are approximations at best), why not just use the Manning's Equation instead? If you know the required Minimum Peak Storm Flow Rate that a segment of the storm drainage pipe needs to convey, all you do is rearrange the formula and solve for Req'd Min. pipe Slope (Ft./Ft.). There are tables for the Manning's Roughness Coefficient (n) available online and in numerous hydraulics handbooks/textbooks for various pipe and channel material types.

And don't forget to check the maximum allowable discharge of the pipe ("Critical Discharge") against your design Peak Flow rate....

It's late and I should be getting into this more with you, as hydraulic design is a forte of mine, but I'm beat and hitting the hay for the night.....

Good luck!

Signed by,

CaptMoosie, PE / PhD

Civil, Structural & Environmental Engineer

I like that answer! I would only add one thing to it. Find the minimum pipe size and go with the next larger size (laid on that previously calculated slope). In reality, no one can build the design exactly at the calculated slope, pipes get fouled, and engineers make assumptions in the calculations. Adding in a little buffer is always prudent.

Hey Chaotic! I like your approach too. I usually do the same same when designing storm sewers with Inlet Control.....

I first know what design storm peak flow rate I must convey and then pick a pipe diameter and gradient.

For any given gravity fed pipe with inlet control (ie, no inlet submergence allowed in structures and no pressure flow...Manning's Eq. basically ignores this and Qcr), I use the following formula for determining Maximum Allowable pipe flow rate (the Critical Discharge rate, Qcr) for any given round pipe:

Qcr = 2.58 * D ^5/2

Pipe Diameter (D) is in feet; Qcr is in CFS.

What?! No hydraulic jumps in your designs??

I would advise looking at WWW.PIPEFLOW.CO.UK for their extremely affordable "Pipe Flow Advisor" program. It allows you to select Manning's coefficient for almost any material, length, internal diameter, fluid depth, drop in feet, etc. You can also add tanks, reservoirs, weirs, etc.

I also use their programs "Pipe Flow Wizard" and "Pipe Flow Expert".

I am a bit curious about the intended purpose for which he needs these flow charts. As previously implied design engineers just run the Mannings Equation calculations on a quick excel spreadsheet (usually adjusting the Mannings coefficient slightly higher than manufacturers use to account for wear and aging of the system).

When I'm not near my PC or laptop to use my Excel Spreadsheets or hydraulics programs, I still use my old trusty HP-41CV Programmable Calculator with several installed hydraulics programs, including the HP "Pipe Slide Rule" line code. IMO, it's still one of the best programmables still out there! I totally dislike the newer ones!

When on the PC running hydrology software, my weapon of choice has always been "HYDROCAD". I LOVE IT, and have been using it almost 20 years now! Neat thing about the program is that you can set it up almost any way to model the way storm sewers actually convey runoff: I usually direct drainage areas to discharge into ponds with known routing stage elevations & volumes. These ponds, with a modeled outlet grate at the bottom of the pond that discharges directly into the catch basin below, which in turn has a known modeled interior volume and outlet pipe....this outlet pipe then discharges to the next catch basin (a pond too) with a discharge pipe that..........and so forth and so forth.

You get the picture. Very accurate and very flexible hydrology software platform. I highly recommend it!

yes i know the feeling, except mine are hp 48gx. Though apparently, those are too programmable, they made them illegal for the National engineering exam a few years ago. Hard to downgrade to calculators that don't use reverse polish notation.

As far as software goes, it all seems to have about the same level of quality, just in slightly differing degrees of advantages/disadvantages, SWMM, StormCAD, HEC (RAS, HMS). It really depends on how i need to apply the software. Since I don't buy it and work for a huge engineering coproation, they decide what we use in bulk, unless a client specifies the product and pays for it. Bentley products being popular, as well as free products from the federal government agencies. Though i guess who ever gives the corporation the best deal with the least accrued risk from usage will become the popular software over time as the company transitions everyone over and they become accustomed.

OK... so I'm well versed in software, programming, computers, spreadsheets, mathcad, hydrocad, etc, etc, etc. I always use the high tech for final designs.

That being said, the very first thing I turn to for an initial design is "the wheel". I never thought slide rules would be the tool of choice for me, but it really is incredible how fast and simple it is to use.

For those of you who don't know what it is, it is a slide rule for pipe design. It adjusts for various "n" values, pipe size and slope. You can acquire one for FREE from the National Clay Pipe Institute's website last I checked.