Quick Answer
Your commercial sewer bill is higher than your water bill for two reasons. First, wastewater treatment genuinely costs more than drinking water treatment, so commercial sewer rates in major U.S. cities commonly run $6 to $15 per thousand gallons — often 1.5 times the water rate or more. Second, utilities bill sewer on 100 percent of the water you purchase, assuming it all reaches the drain. For a building with a cooling tower evaporating 25 to 40 percent of its water, that assumption charges full sewer rates on water the treatment plant never receives. The rates themselves aren’t negotiable, but the billed volume is: sewer credits let you pay sewer charges only on water that actually enters the sewer.
You’re not imagining it — for most commercial buildings, the sewer portion of the utility bill is larger than the water portion, sometimes significantly so. If you’ve noticed that your sewer charges run 20, 50, or even 100 percent higher than your water charges, there’s a structural reason for it. Understanding why it happens is the first step toward doing something about it.
Why Sewer Rates Are Higher
Treating wastewater is more expensive than treating drinking water. Municipal wastewater treatment plants must remove biological contaminants, chemical pollutants, suspended solids, and nutrients like nitrogen and phosphorus before the water can be safely discharged. This requires multi-stage processing — screening, primary settling, biological treatment, secondary clarification, disinfection, and often advanced nutrient removal. The energy, chemical, and labor costs of this process are substantial.
Aging sewer infrastructure adds another cost layer. Many American cities are dealing with sewer systems that are 50 to 100 years old, facing billions in repair and replacement costs. These capital expenses get passed to ratepayers. The U.S. Environmental Protection Agency reports that wastewater infrastructure needs across the country exceed $270 billion, and those costs are increasingly reflected in higher sewer rates.
Additionally, federal and state regulations on wastewater discharge quality have tightened significantly over the past two decades. Plants must meet stricter standards for nutrient levels, emerging contaminants, and combined sewer overflow management — all of which require capital investment that drives rates up.
The Billing Assumption That Makes It Worse
Higher sewer rates alone explain why sewer charges exceed water charges. But for commercial buildings with cooling towers, the billing assumption makes the problem even worse. Your sewer bill is calculated on the assumption that all the water you purchase ends up in the sewer system. For a building evaporating 30 to 40 percent of its water through a cooling tower, this means you’re paying the higher sewer rate on water that never reaches the treatment plant.
Consider the math. A building uses 400,000 gallons per month. Water costs $6 per thousand gallons ($2,400), and sewer costs $9 per thousand gallons ($3,600). The sewer bill is already 50 percent higher. But if the cooling tower evaporates 120,000 gallons, the building only sends 280,000 gallons to the sewer — meaning $1,080 of that sewer charge is for water the treatment plant never received. That’s the billing assumption at work, and it’s costing you real money.
How to Read the Sewer Charges on Your Bill
Commercial utility bills bury the story in line items, and knowing what each one means helps you spot overcharges. The volumetric sewer charge is the big one — a per-thousand-gallon or per-CCF rate (one CCF is 748 gallons) applied to your metered water consumption. A fixed service charge based on meter size appears on both the water and sewer sides, and an oversized meter inflates it every month regardless of usage.
Some utilities add wastewater strength surcharges for high-strength discharge, measured as BOD and TSS — mostly relevant to restaurants and industrial users, but worth confirming you’re classified correctly. Many bills also carry a separate stormwater fee based on impervious surface area; it looks like a sewer charge but is calculated differently and is not reduced by sewer credits. Finally, check which meter each charge references — buildings with multiple meters sometimes pay sewer charges on an irrigation meter that should be exempt.
Three Numbers to Pull From Your Last 12 Bills
Before calling anyone, gather a year of bills and extract three numbers. First, your effective sewer rate: total sewer charges divided by total billed volume. Compare it against your utility’s published rate schedule to catch classification errors. Second, your sewer-to-water ratio: if sewer runs more than double your water charges, the payoff from a credit is that much larger. Third, your summer-to-winter consumption swing: for buildings without irrigation, most of that seasonal spread is cooling tower evaporation — exactly the volume a sewer credit removes from your bill. Together, those three numbers tell you whether you have a rate problem, a volume problem, or both.
What You Can Do About It
The most direct solution is applying for sewer credits. A sewer credit reduces your sewer charges to reflect only the water that actually enters the sewer system. For buildings with significant non-sewer water uses — cooling tower evaporation, irrigation, boiler losses — the savings can be dramatic. In the example above, a sewer credit would reduce the monthly sewer bill from $3,600 to $2,520, saving $1,080 per month or nearly $13,000 per year.
The Department of Energy’s cooling tower management guidance recommends that facilities track evaporation losses and pursue available utility credits as part of responsible water management — it’s considered standard best practice, not an aggressive financial maneuver.
Beyond sewer credits, consider whether your building’s meter size is appropriate for your actual peak flow. Oversized meters carry higher fixed charges on both the water and sewer side. And look at your rate classification — some utilities have different rate tiers for different building types, and a reclassification might reduce your per-unit cost.
Ready to Find Out What You Could Save?
RPM Water Equity Solutions helps commercial facilities recover money lost to sewer billing assumptions. If your building has cooling towers, you may be paying sewer charges on water that never reaches the sewer system.
Request your free assessment today and find out how much you could recover.
Stop Paying for Someone Else’s Sewage Treatment
When your sewer bill exceeds your water bill and your building is evaporating tens of thousands of gallons through a cooling tower, you’re essentially subsidizing the treatment of water that never reaches the treatment plant. Sewer credits exist precisely to correct this inequity. The rates themselves are beyond your control — but the amount of water those rates apply to is very much within your power to change.
