How Stepped Tariffs Work in Municipal Water Billing
Learn how Ekurhuleni's 7-tier stepped water tariff works and why getting it right matters for accurate body corporate billing.
#What Are Stepped Tariffs?
Municipal water pricing in South Africa doesn't use a flat rate. Instead, consumption is divided into tiers (or steps), each with a progressively higher rate per kilolitre. The more water a household uses, the more expensive each additional kilolitre becomes.
This is called a rising block tariff or stepped tariff structure.
#Ekurhuleni's 7-Tier Water Tariff
Ekurhuleni Metropolitan Municipality uses a 7-tier structure for domestic water:
| Tier | Range (kl) | Rate per kl |
|---|---|---|
| 1 | 0 – 6 | R0.00 (Free Basic Water) |
| 2 | 7 – 10 | R12.85 |
| 3 | 11 – 15 | R18.48 |
| 4 | 16 – 20 | R24.26 |
| 5 | 21 – 30 | R30.12 |
| 6 | 31 – 45 | R37.45 |
| 7 | 46+ | R48.92 |
Rates shown are illustrative. Actual rates are updated annually.
#Why This Matters for Body Corporates
When a sectional title scheme has a bulk meter from the municipality and sub-meters for each unit, the managing agent needs to:
- Calculate each unit's charge using the correct stepped tariff
- Ensure the sum of individual charges reconciles with the bulk municipal bill
- Allocate any variance fairly
#The Common Mistake
Many managing agents calculate individual charges using a blended rate — dividing the total bill by total consumption. This seems simpler but produces inaccurate results because it ignores the stepped structure.
A unit consuming 8kl pays a different per-kl rate than a unit consuming 40kl. Blended rates effectively subsidise heavy users at the expense of light users.
#The Correct Approach
Each unit's consumption must be run through the tariff tiers independently. A unit using 12kl is charged:
- 6kl at Tier 1 (free)
- 4kl at Tier 2
- 2kl at Tier 3
This produces a precise per-unit charge that matches what the municipality would charge if each unit had its own connection.
#How EstateFlow Implements This
EstateFlow's billing engine processes each sub-meter reading through the full stepped tariff:
- All 7 tiers are applied per-unit with cent-level precision
- Banker's rounding ensures financial accuracy
- Largest-remainder allocation handles the variance between bulk and sub-meter totals
- The engine is a pure function with zero side effects — fully testable and auditable
The result: every unit pays exactly what they should, and the numbers always add up.