Once facility managers realize their building has been paying sewer charges on water that evaporates from a cooling tower, the first question is usually: “Can I get that money back?” It’s a fair question — if you’ve been overpaying for years, the total can be staggering. Here’s what to realistically expect.
The Honest Answer: Usually No — But Going Forward, Yes
Most utilities apply sewer credits prospectively, meaning they start from the date your application is approved going forward. They don’t typically issue retroactive refunds for months or years of past overpayments. The reasoning from the utility’s perspective is straightforward: you didn’t have metering data to prove the non-sewer water use during those prior periods, so there’s no documentation to base a refund on.
That said, some utilities offer limited retroactive adjustments — typically one to three billing cycles back from your application date. A few cities with more progressive programs may go back further if you can provide convincing engineering estimates of historical evaporation. It’s always worth asking, but don’t build your business case around retroactive recovery.
How to Calculate What You’ve Been Losing
Even if you can’t recover the past, it’s useful to understand the magnitude. A mid-rise office building with a 400-ton cooling tower typically evaporates 80,000 to 120,000 gallons per month during the cooling season. At a sewer rate of $8 to $12 per thousand gallons — rates that the EPA notes have been rising steadily — that’s $640 to $1,440 per month in excess sewer charges. Over five years of inaction, that’s $38,000 to $86,000 that went to the utility for sewer treatment of water that went into the sky.
The lesson isn’t to dwell on what’s lost — it’s to stop the bleeding as quickly as possible.
Why the Payback Period Is So Short
The good news is that even without retroactive refunds, the return on investment for a sewer credit program is remarkably fast. The cost of installing submeters and applying for credits typically runs $2,000 to $8,000, depending on the complexity of your plumbing and your city’s requirements. If your building saves $1,000 per month in sewer charges (a conservative estimate for most cooling tower facilities), the entire investment pays for itself in two to eight months.
Our detailed analysis of water monitoring ROI breaks down these numbers across different building types and sizes. The payback periods are consistently measured in months, not years — making sewer credits one of the fastest-returning capital investments a facility can make.
What You Can Do Right Now
If you believe your building has been overpaying, take three immediate steps. First, call your utility and ask specifically whether retroactive credits are available — you might be surprised. Second, request information about their sewer credit application process so you can start the clock on prospective savings. Third, get your cooling tower metered so you have the data you need. The Department of Energy recommends metering as a fundamental best practice for cooling tower management, and the data serves multiple purposes beyond just sewer credits.
For a detailed look at how billing assumptions create these overpayments in the first place, our article on how much you’re overpaying for sewer lays out the math clearly.
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.
Focus on the Future
It’s natural to be frustrated about past overpayments, but the most productive response is to act quickly on future savings. Every month you spend researching whether you can recover the past is another month of new overpayments. The math is simple: the sooner you apply, the sooner the savings start. Don’t let the perfect be the enemy of the good — start your application now and let the ongoing savings accumulate.
