Finding water and sewer overcharges on commercial bills

Most commercial teams treat the water bill as a small, fixed cost and pay it without a second look. That habit is expensive, for two reasons. Water and sewer rates are rising fast, and the sewer charge, which is usually the larger half of the bill, is often calculated on water that never reaches the sewer at all. Both problems are fixable once you can see the bill clearly.

Rates first. Analysis of United States municipal water rates found the typical household water and sewer bill rose about 24 percent over five years, with sewer charges making up roughly 59 percent of the monthly bill. Longer term, the American Water Works Association projects average annual household drinking-water bills rising from about $429 in 2025 to $969 by 2050 as infrastructure needs mount. A cost that grows this fast deserves a closer look than a rubber stamp.

Why sewer charges are the place to start

Here is the mechanism that drives most sewer overcharges. Utilities cannot easily meter what goes down the drain, so they estimate it from what comes out of the tap: your sewer charge is calculated from your metered water use. That is a reasonable proxy for an office where nearly all water goes down a drain. It is badly wrong for any site where large volumes of water are used but never enter the sewer.

Many residential utilities correct for this with winter averaging, basing sewer charges on water used in winter months when it can be reasonably assumed that virtually all water is used indoors and returns to the sewer, excluding summer irrigation. Commercial accounts are frequently billed on actual monthly water instead, which means every gallon that evaporates, irrigates, or ends up in a product is charged a sewer fee it should never carry.

Where the overcharges hide

Irrigation billed as sewage

Water used for landscaping goes into the ground, not the sewer, yet without a separate irrigation meter it is charged both a water and a sewer fee. Industry guidance is explicit that you should not be charged for wastewater when water is used for irrigation only, and utilities can meter that use and issue a credit. A deduct meter or a dedicated irrigation meter removes the sewer charge on that volume.

Cooling tower evaporation

Cooling towers are one of the clearest cases. In a typical tower, around 75 percent of the water evaporates and never drains to the sewer, yet the site is charged twice, once to deliver the water and again to treat wastewater that was never produced. An evaporation credit, supported by a submeter on the tower makeup line, removes the sewer charge on the evaporated portion. For a building with significant cooling load, this single correction can be substantial.

Process water and other non-sewer use

Any water that leaves as product, is consumed in a process, or is otherwise not discharged is a candidate for a sewer deduct. Bottling, food processing, and manufacturing all have volumes that never reach the drain, and all of them are billed sewer fees by default unless a deduct meter says otherwise.

Meter, rate, and stormwater errors

Beyond the water-versus-sewer split, commercial water bills carry the same error types as any utility bill: estimated reads that never true up, the wrong rate tier or meter multiplier, and charges for supplies that are inactive. Stormwater fees add another layer, because they are billed not on water use but on measured impervious surface, converted to equivalent units and often read from aerial imagery. An error in that measured area drives an overcharge that has nothing to do with how much water you use.

Do not overlook leaks

Not every high bill is a billing error. Some are real water you are losing. EPA WaterSense estimates that household leaks waste nearly 1 trillion gallons of water annually across the country, and fixing easily corrected leaks can save about 10 percent on a water bill. On a commercial site, a running irrigation valve or a failed float can push both water and sewer charges up for months. Structured, monitored consumption data is how you tell a leak apart from a billing error, because both show up as a number that does not fit the site history.

Why manual review misses these

These charges survive because a person paying a stack of monthly bills has no way to see them. The sewer overcharge is buried in a proxy calculation. The estimated read looks like any other line. The evaporation credit is one you have to know to ask for. Catching them at portfolio scale means reading every field on every water and sewer bill and checking it against the tariff, the meter configuration, and the site history, which is not work a spreadsheet does well.

How MartinAI helps

MartinAI reads every water and sewer bill across your sites, extracts the usage, the sewer basis, the rate, the meter, and the period, and validates those figures against the tariff and against each account's own history. Once the data is structured, the patterns that signal an overcharge stand out: a sewer charge that tracks irrigation season, a cooling-tower site with no evaporation credit, an estimated read that never corrected, a consumption jump that looks like a leak.

The result is that your team spends time only on the bills that genuinely look wrong, with the evidence already assembled to raise a correction or request a deduct. You stop paying sewer fees on water that never reached the sewer, and you catch the leaks and misreads before they run for a year.