Hydraulic Engineering Center

Engineering reference Project verification required

Engineering disclaimer: Calculators and methods on this page are engineering references for education and preliminary design discussion. They are not a substitute for project specifications, PE-stamped calculations, or ALFA confirmation of product ratings for your service conditions. Project-specific verification required.

Purpose

Help engineers choose and apply the right hydraulic method for thermoplastic pressure and gravity systems using metric units common on Saudi projects (mm, L/s, m³/h, m/s, bar, kPa, m head).

When to use which equation

Method	Typical use	Key inputs	Caution
Hazen–Williams	Water distribution friction education / many municipal water models	Q, ID, L, C (user/assumption)	Empirical; water-oriented; not universal
Darcy–Weisbach	Re-based design, non-water fluids, consultant preference	Q, ID, L, ε, ν → f	Needs credible roughness & viscosity
Manning	Open channel / gravity full or partial flow (partial needs separate geometry)	D, slope, n	Full-bore tool ≠ partial-flow design

No single equation is universally superior. Follow the project hydraulic basis of design.

Workflow — pressure systems

Define design flow (L/s or m³/h) and diversity/coincidence rules from the designer.
Select candidate ID from product wall/SDR data (not DN alone).
Compute velocity; review against project velocity guidance.
Compute friction (HW or Darcy); add minor losses via K or equivalent length.
Check static + dynamic head against pump / available pressure.
Review temperature derating of pressure rating in parallel.

Workflow — gravity systems

Confirm sanitary vs storm vs combined duty and design storm/peak factors.
Set invert/slope from alignment; verify self-cleansing criteria in the project specification.
Use Manning carefully for full vs partial flow; do not invent capacity tables.
Coordinate manholes, drops, and connections with civil detailing.

Coefficient honesty

C-factor / Manning n / ε — mark as user input or engineering-reference default.
Never present assumed C = 150 or n = 0.009 as an ALFA-certified value.

Related resources

Hazen–Williams Darcy–Weisbach Manning Reynolds Equivalent length Flow velocity

Technical support

Talk to an engineer Request technical submittal

Related products & tools

Hazen–Williams calculator Darcy–Weisbach calculator Manning calculator Pressure pipe products

Direct technical answer: Hydraulics

This engineering resource explains Hydraulics for designers and reviewers. Use it to clarify definitions, methods, and limitations—then apply project-specific data.

Method, assumptions, and limits

Document formulas and variable definitions when performing calculations. Call out where soil modulus, temperature derating, or surge dominates the result. Link outcomes back to product standards and application hubs for procurement.

Related: products · applications · standards index.

Frequently asked questions

What information is needed to quote Hydraulics?

Standard, size/pressure class, jointing system, quantities/lengths, fittings list, delivery location, and any submittal/test requirements from the specification.

Can I substitute one pipe standard for another at the same nominal size?

Not without review. Dimensions, pressure classes, and test methods differ across standard families.

How do I contact ALFA for supply?

Use the RFQ form or contact +966 50 183 5126 / sales@alfaalarabia.co. Manufacturing is based at 3rd Industrial City, Jeddah, Kingdom of Saudi Arabia (Aramco Vendor #10116102).

Related resources

Batch-1 knowledge update: ALFA-specific order data must come from approved submittals—this section does not invent ratings or certifications.