Why sewer charges may not follow this month’s water use
A water meter measures water entering the property. Sewer charges may use that volume, an earlier seasonal reference or another billing basis. Check both quantities before combining their prices.
Read the sewer basis on its own
Homes often have no separate wastewater meter. The tariff defines billable sewer volume. Some systems use current water consumption; others use a winter reference to limit the effect of outdoor watering. Reference months, caps and rules for new accounts vary. A local rule is not a universal sewer formula.
One statement, two quantities
Consider a fictional month with 18 m³ of water at USD 2/m³ and 10 m³ of billable sewer volume at USD 3/m³. With separate fixed charges of USD 8 and USD 12, the total is 18 × 2 + 10 × 3 + 8 + 12 = USD 86 before tax. Combining prices into USD 5/m³ and multiplying by 18 produces USD 110 including fees, overstating this example by USD 24.
What does an avoided cubic meter change?
Under this example’s fixed sewer basis, reducing summer garden use by 1 m³ reduces the water line by USD 2 while sewer stays unchanged. If both services billed current volume, the avoided variable charge would be USD 5. A winter reduction might affect a later reference, depending on the tariff.
Run the Bill Calculator separately for each service using its own quantity, fee and tax treatment. Ask the supplier which months set the sewer basis and whether an irrigation meter or verified leak qualifies for an adjustment. Keep repair evidence if applying. Neither a calculator result nor proof that water stayed outside guarantees a credit.
Electricity & Water Bill Calculator
Worked example: Combine water and sewer unit charges
Related reading: Read the units on your water bill
Reference: Austin Water: wastewater averaging.