Q1, Q2, Q3, Q4 Explained: Why Flow Ranges Matter in Water Meter Selection

When selecting a water meter, the terms Q1, Q2, Q3, and Q4 are key indicators of performance. These refer to the flow ranges defined by ISO 4064 / OIML R49:

• Q1: Minimum flow where readings remain valid

• Q2: Transitional flow range

• Q3: Permanent (nominal) flow for daily use

• Q4: Overload flow, the meter’s upper limit

Why is this important?
✔️ Prevents inaccurate billing
✔️ Ensures meters perform under varying conditions
✔️ Guarantees compliance with international standards

For utilities, industries, and smart city projects, choosing the right Q-class water meter is critical for reliability, fairness, and future-proof water management.