WAG Hydraulic Documentation Standards: The Complete Guide

Hydraulic documentation should make a wildfire protection system understandable, reviewable, testable and maintainable long after installation. These standards define the minimum information needed to show how water moves through a property, what assumptions govern system performance and how field results compare with the design basis.

Purpose of Hydraulic Documentation

Hydraulic documentation should establish a traceable connection between property risk, water supply, system configuration, expected performance and measured results. A reviewer should be able to determine what the system is intended to do, what operating conditions were assumed and whether the completed installation meets those assumptions.

Required Document Set

• Hydraulic design narrative
• Water-source and available-supply data
• System demand calculations
• Pipe-network drawings and node schedules
• Pump and pressure-control documentation
• Water-storage and usable-volume calculations
• Operating-sequence assumptions
• Commissioning and field-test results
• Final as-built hydraulic record

Design Basis and Performance Objectives

The documentation should state the required flow, pressure, duration and operating sequence at the defined point of connection. It should identify the structures, exposure areas or nodes included in the calculation and clearly distinguish required performance from optional design margin.

Water-Source Documentation

Every source should be identified by type, location, ownership and operating limitations. Well yield, municipal supply, irrigation storage, ponds, pools, cisterns and transfer sources should be documented separately. Shared or seasonal sources require clear assumptions about competing demand and availability during wildfire conditions.

Flow-Test Standards

Field flow tests should record test date, test location, elevation, static pressure, residual pressure, measured flow, test duration, instrument type and calibration status. Results should identify whether testing occurred at the actual system connection or at a remote point requiring adjustment.

Elevation and Pressure Datum

All critical elevations should use a consistent datum. The documentation should identify source elevation, pump elevation, high and low discharge points and the hydraulic reference point used for pressure requirements. Unexplained elevation differences are a frequent cause of misleading pressure calculations.

Demand Calculations

Demand should be based on the actual operating strategy rather than the sum of every discharge device on the property unless simultaneous operation is intended. Calculations should show node flow, number of concurrent nodes, control sequence, overlap, flushing demand and any reserve capacity.

Pipe-Network Documentation

Pipe calculations should identify material, nominal size, actual internal diameter, length, fitting allowance, elevation change and flow through each segment. Underground, above-grade and concealed piping should be distinguishable. Shared mains and branch points should be clearly labeled.

Friction-Loss Method

The selected calculation method, coefficients and assumptions should be stated. The documentation should not mix friction methods or pipe coefficients without explanation. Valves, filters, meters, backflow devices, check valves and specialty fittings should be included using documented loss values.

Node and Discharge-Device Schedules

Each node should have a permanent identifier tied to drawings, controls and field labels. The schedule should include device type, orifice or nozzle model, intended flow, required pressure, elevation, branch size, coverage purpose and control address.

Pump Selection Documentation

Pump records should include manufacturer, model, impeller or stage configuration, rated speed, motor size, voltage, phase, efficiency assumptions and the selected operating point. The system curve and pump curve should be shown together when practical.

Variable-Frequency and Pressure-Control Systems

Variable-frequency drives, pressure transducers, pressure tanks and control setpoints should be documented as part of the hydraulic design. Minimum speed, maximum speed, sleep settings, restart logic and low-water protection can materially affect performance and should not be treated only as electrical settings.

Storage and Usable-Volume Calculations

Nominal tank capacity should not be presented as usable wildfire reserve. Calculations should account for suction elevation, dead storage, overflow, operating level, sediment allowance, shared domestic demand and minimum pump submergence. Required runtime should be tied to the actual operating sequence.

Filtration and Water Quality

Filter size, screen rating, clean pressure loss, allowable dirty pressure loss and flushing demand should be included. Water quality limitations that may affect nozzles, valves, pumps or sensors should be identified, along with the maintenance assumptions used in the design.

Operating Scenarios

Documentation should evaluate the scenarios that govern performance. These may include normal grid operation, backup power, low storage, alternate water source, single-pump failure, filter loading, high-elevation node operation and simultaneous domestic or irrigation use.

Available Versus Required Performance

Calculations should clearly compare available flow and pressure with required flow and pressure at the controlling node. The hydraulic margin should be stated rather than implied. Excessive margin should not be used to conceal uncertain inputs or incomplete testing.

Surge and Transient Considerations

Where rapid valve operation, long mains, high pressure or significant elevation changes are present, the documentation should identify surge risks and the measures used to manage them. These may include controlled valve timing, pressure relief, air management, accumulators or modified operating sequences.

Freeze and Drain-Down Impacts

Dry, seasonal and low-pressure standby systems require hydraulic documentation for filling, purging, draining and restoring the system. High points, low points, trapped sections, air-release devices and drain locations should be shown on the drawings.

Calculation Assumptions and Unverified Inputs

Every significant assumption should be listed. Inputs based on owner statements, record drawings, estimated pipe routes or unverified equipment should be identified as provisional and carried into the field-verification plan.

Commissioning Correlation

Final field testing should use the same reference points and operating scenarios as the design calculations. Measured flow, pressure, speed, current, storage drawdown and runtime should be compared directly with the documented design basis.

Acceptance Tolerances

The design team should define acceptable variation between calculated and measured results. Tolerances should account for instrument accuracy and reasonable field variation but should not excuse failure to meet the required minimum performance.

Change Management

Changes to pipe size, routing, elevation, nozzle model, pump selection, filter configuration, water source or operating sequence require hydraulic review. The final calculation package should reflect the installed system rather than the original proposal.

File Organization and Revision Control

Hydraulic files should include project name, property address, preparer, reviewer, revision date and document status. Superseded calculations should be retained but clearly marked. Final records should be provided in both readable PDF form and the native calculation format when available.

Good, Better and Best Documentation Programs

Good

A clear design narrative, verified supply test, demand summary, basic pipe-loss calculations, pump selection and commissioning results.

Better

A complete node-by-node model with source limitations, operating scenarios, storage runtime, field verification and formal calculation review.

Best

A fully coordinated property hydraulic model linked to as-built drawings, asset registers, control sequences, backup-power scenarios, integrated testing and recurring performance benchmarks.

Common Documentation Mistakes

• Using nominal pipe size instead of actual internal diameter
• Ignoring elevation or using inconsistent pressure reference points
• Listing tank capacity without usable-volume analysis
• Assuming pump performance from horsepower alone
• Omitting filter, valve and specialty-equipment losses
• Calculating every device simultaneously when controls operate sequentially
• Failing to reconcile calculations with commissioning results
• Leaving substitutions and field changes out of the final model

Hydraulic Documentation Checklist

• Performance objective and reference point defined
• Water source tested and documented
• Elevations verified
• Demand and operating sequence documented
• Pipe sizes, materials and lengths verified
• Equipment losses included
• Pump operating point documented
• Usable water reserve calculated
• Controlling node identified
• Backup and failure scenarios reviewed
• Commissioning results compared with design
• Final as-built calculation package issued

Technical FAQs

Is a pump curve enough to document hydraulic performance?

No. A pump curve must be evaluated against the complete system curve, elevation, equipment losses and intended operating sequence.

Should static pressure be used for system sizing?

Static pressure alone is not sufficient. Available performance should be based on residual pressure at the required flow.

Can nominal tank volume be used for runtime calculations?

No. Runtime should use verified usable volume after dead storage, suction limitations and shared demand are considered.

When should hydraulic calculations be updated?

They should be updated whenever source conditions, pipe routing, pipe size, pump selection, discharge devices or operating sequences change.

Should field test results be included in the final package?

Yes. Final hydraulic documentation should show both the design expectation and the measured commissioning baseline.