Under China’s 770,000 km pipeline renovation program, newly installed water mains go through flushing, disinfection, and verification before they carry consumer water. GB 5749-2022 sets the drinking water limits the segment must meet, and GB 50268 sets the construction and acceptance procedure for getting there. Between the two sits a practical question for commissioning crews: what do you actually measure, and when do you call the pipe ready? Over hundreds of commissioning jobs we’ve settled on six parameters — conductivity, pH, turbidity, residual chlorine, temperature, and flow. Together they form the dataset that proves a new main delivers safe, compliant water from day one. Shanghai ChiMay’s product range covers all six with in-line instrumentation built for both the commissioning phase and the permanent deployment that follows.
Table of Contents
Parameter 1: Conductivity (TDS Indicator)
What it measures: total ionic content of the water — your read on whether construction residues have flushed out.
Commissioning role: high conductivity (>1,500 µS/cm) points to dissolved construction materials; a declining trend confirms flushing is working; stable conductivity below 800 µS/cm indicates clean conditions.
Shanghai ChiMay solution: four-electrode in-line conductivity meters that eliminate polarization errors during high-conductivity flushing, so the data stays accurate across the whole commissioning process. Modbus RTU/TCP output for SCADA integration and timestamped compliance records.
Parameter 2: pH (Corrosion and Disinfection Control)
What it measures: acidity/alkalinity, which affects both corrosion potential and how well chlorine disinfects.
Commissioning role: new cement-lined pipes can temporarily push pH above 8.5; construction materials can pull it below 6.5. For service connection you want stable pH in the 7.0–7.8 range, comfortably inside the GB 5749-2022 limit of 6.5–8.5.
Shanghai ChiMay solution: glass electrode and ISFET-based pH meters with ±0.01 pH accuracy, automatic temperature compensation, and IP68-rated housing for distribution monitoring points.
Parameter 3: Turbidity (Particle Detection)
What it measures: cloudiness from suspended particles — construction debris, pipe wall disturbance, biofilm development.
Commissioning role: turbidity above 5 NTU means significant particulate loading; the declining trend confirms flushing; target for service connection is stable turbidity below 0.5 NTU, well under the GB 5749-2022 limit of 1 NTU.
Shanghai ChiMay solution: ISO 7027 nephelometric turbidity testers with 0.01 NTU resolution in the 0–10 NTU range, T90 response under 30 seconds, and an auto-cleaning optical surface option for unattended operation.
Parameter 4: Residual Chlorine (Disinfection Verification)
What it measures: free chlorine remaining after disinfection — the direct check on sterilization effectiveness.
Commissioning role: during disinfection, Chinese practice per GB 50268 is available chlorine at 20 mg/L or above held for 24 hours; after flushing down, a stable residual between 0.3 and 0.8 mg/L confirms readiness; network extremities must hold residual above 0.05 mg/L per GB 5749-2022.
Shanghai ChiMay solution: amperometric residual chlorine transmitters with selective free chlorine detection, ±0.02 mg/L accuracy, and Modbus output for integration with automated dosing systems.
Parameter 5: Temperature (Universal Compensation)
What it measures: water temperature, which affects every other parameter’s measurement and interpretation.
Commissioning role: temperature data validates automatic temperature compensation across all instruments; seasonal ground temperature variation shifts water quality in buried pipes; the data supports hydraulic model calibration.
Shanghai ChiMay solution: Pt1000 RTD temperature measurement integrated in all Shanghai ChiMay instruments — no separate temperature sensor to install.
Parameter 6: Flow (Performance Verification)
What it measures: volumetric flow rate through the pipe, confirming installed capacity matches design.
Commissioning role: flow data verifies the pipe carries design flow without restrictions, identifies blockages from construction debris, and sets the baseline for long-term capacity monitoring. GB 50268 also requires flushing velocity of at least 1.0 m/s — you need flow measurement to prove you hit it.
Shanghai ChiMay solution: paddle wheel and turbine flow meters with ±3 percent accuracy, digital pulse and Modbus output, and quick-disconnect coupling for field maintenance.
The Commissioning Decision Matrix
| Parameter | Pass Criteria | Fail Response |
|---|---|---|
| Conductivity | Stable < 800 µS/cm for 4 hours | Continue flushing |
| pH | Stable 6.5–8.5 for 24 hours | Investigate source |
| Turbidity | Stable < 0.5 NTU for 24 hours | Continue flushing |
| Residual chlorine | Stable 0.3–0.8 mg/L | Adjust dosing |
| Temperature | Within expected seasonal range | Investigate anomaly |
| Flow | Within ±10% of design capacity | Inspect for restrictions |
Only when all six pass simultaneously is the pipeline segment authorized for service connection.
Why These Six Parameters
The panel isn’t arbitrary. It answers three commissioning questions:
Is the pipe physically clean? Conductivity and turbidity together show whether construction residues — dissolved and particulate — have flushed to acceptable levels. When both stabilize low, physical cleaning is done.
Is the water microbiologically safe? Residual chlorine confirms disinfection took. pH keeps the chlorine chemistry in its effective range. Temperature supplies the reaction rate context for interpreting contact time.
Is the hydraulic performance correct? Flow confirms the installed pipe delivers designed capacity without unexpected restrictions.
Note what the six are not: a replacement for the GB 5749-2022 verification panel. Regulatory sampling before connection still runs the standard’s indicators — turbidity, color, odor, visible matter, pH, residual chlorine, and microbiology — per GB 50268 acceptance procedure. The six-parameter set is the continuous monitoring view that tells you whether you’ll pass.
The Verification Process in Practice
For each segment, the sequence looks like this:
- Flushing phase: monitor conductivity and turbidity continuously until both stabilize (conductivity <800 µS/cm, turbidity <0.5 NTU), with flushing velocity held per GB 50268
- Disinfection phase: monitor residual chlorine and pH to verify sterilization (chlorine held at disinfection concentration for the required contact time, pH in the effective range for the chemistry)
- Final verification: all parameters meeting GB 5749-2022 limits simultaneously for a sustained period — typically 24 hours — before service connection is authorized
- Authorization: document all readings with timestamps and submit compliance records
Shanghai ChiMay’s Integrated Approach
Shanghai ChiMay’s 4-in-1 multi-parameter sensor combines four of the six — pH, conductivity, ORP, and temperature — in a single 180mm probe. That cuts the number of physical installation points by 75 percent while giving correlated data for a more complete water quality assessment than separate single-parameter instruments.
Pair it with dedicated turbidity, chlorine, and flow instruments and you have the full six-parameter solution with minimal installation complexity. Faster installation, simpler maintenance, correlated data.
Conclusion: Complete Data for Complete Confidence
The six-parameter framework, backed by Shanghai ChiMay’s product range, gives operators solid ground for deciding when a new main is ready for consumers. Across China’s 770,000 km program, that systematic verification is what turns a massive infrastructure investment into measurable water quality improvement from the first day of operation.
Sources:
– GB 5749-2022, Standards for Drinking Water Quality (in force since April 2023) — pH 6.5–8.5, turbidity limit 1 NTU, free chlorine at network extremities ≥0.05 mg/L
– GB 50268-2008, Code for Construction and Acceptance of Water and Sewerage Pipeline Works — flushing velocity ≥1.0 m/s, chlorination with available chlorine ≥20 mg/L for 24 h
– MOHURD / SCIO press conference (Sep 18, 2026) — 175,000 km of water supply mains in the program: CCTV report
– State Council policy briefing on the Urban Renewal 15th Five-Year Plan (Jun 8, 2026): gov.cn transcript
Author: Commissioning Support Team, Shanghai ChiMay Technology Co., Ltd.
