How Much Can My Building Save with Sewer Credits?

It’s the first question every facility manager asks: how much money are we actually talking about? The answer depends on your building type, cooling system size, and local sewer rates — but the math is surprisingly simple, and you can get a rough estimate in about two minutes.

The Quick Estimation Formula

Here’s the back-of-the-envelope calculation: take your monthly sewer charge and multiply it by the estimated percentage of your water that doesn’t reach the sewer system. That percentage is your savings potential.

Monthly Savings = Monthly Sewer Charge × Non-Sewer Water Percentage

For example, if your monthly sewer bill is $5,000 and your cooling tower evaporates roughly 25 percent of your total water use, your potential savings are approximately $1,250 per month — or $15,000 per year. It’s not exact (actual credits are based on metered data, not estimates), but it gives you a reliable order of magnitude to work with.

Typical Savings by Building Type

The non-sewer water percentage varies significantly by building type because different facilities have different water use profiles. Based on industry data and our experience working with commercial clients, here are typical savings ranges:

Office buildings with cooling towers typically save 15 to 30 percent on sewer charges. Cooling towers are usually the only significant non-sewer water use, but they can be substantial. A 500-ton tower serving a large office complex might evaporate 80,000 to 120,000 gallons per month during summer. The Department of Energy estimates that evaporation accounts for the majority of cooling tower water consumption.

Hotels and hospitality save 20 to 35 percent because they have multiple non-sewer water uses: cooling tower evaporation, pool evaporation and backwash, laundry water losses, and landscape irrigation. These sources stack to create a larger total credit.

Universities and campus facilities often save 25 to 40 percent. Large campuses may have multiple cooling towers, central boiler plants with steam losses, extensive irrigation systems, and laboratory process water — all of which qualify for credits in most jurisdictions.

Retail centers and malls typically save 10 to 25 percent. Savings depend heavily on whether the property has a central plant with cooling towers versus individual rooftop units (which generally don’t qualify for significant credits).

Real Dollar Amounts

To put percentages into dollars, consider that commercial sewer rates in major U.S. cities range from $6 to $15 per thousand gallons, according to EPA water rate data. A mid-size commercial building using 400,000 gallons per month at $10 per thousand gallons pays $4,000 monthly in sewer charges. A 25 percent credit saves $1,000 per month, or $12,000 per year.

Larger facilities see proportionally larger savings. A university campus with multiple towers and $25,000 in monthly sewer charges saving 35 percent recovers $8,750 per month — over $100,000 per year. Our ROI case studies document real facilities achieving savings in these ranges.

Why Estimates Are Just the Beginning

The formula above gives you a starting point, but actual savings are determined by metered data — not estimates. Your cooling tower’s evaporation rate depends on weather, operating hours, cycles of concentration, and equipment condition. The only way to know your exact savings potential is to install meters and measure. That said, the estimate tells you whether the savings justify the investment in metering — and for virtually any building with a cooling tower over 200 tons, the answer is yes.

For a detailed breakdown of what submetering costs and how quickly it pays for itself, see our water monitoring ROI analysis.

Don’t Guess — Measure

Your estimate gives you a reason to act. Metered data gives you the exact number. RPM’s free assessment can tell you precisely what your building would save based on your specific equipment, water use, and local sewer rates — no guessing required.