When most people think of sewer credits, they think of cooling towers — and for good reason, since cooling tower evaporation is typically the largest non-sewer water use in a commercial building. But cooling towers aren’t the only qualifying water use. Boiler systems, particularly in buildings with steam heating, can also generate significant sewer credit savings that many facility managers overlook.
How Boilers Lose Water
Steam boiler systems lose water through several mechanisms that parallel cooling tower losses. The most obvious is steam that’s generated and distributed throughout the building for heating — some of this steam is consumed (vented to atmosphere through safety valves, cooking equipment, or humidification systems) and never returns to the boiler as condensate. This is water that enters your building through the meter but never reaches the sewer.
Boiler blowdown is another qualifying loss. Like cooling towers, boilers concentrate dissolved minerals as water evaporates into steam. Regular blowdown removes this concentrated water — and while blowdown water does go to the sewer, the steam losses do not. Additionally, condensate return losses from leaking steam traps, failed condensate pumps, or condensate that’s deliberately dumped (in once-through steam systems or where condensate is contaminated) represent water that left the boiler room but didn’t reach the sewer.
The U.S. Department of Energy’s guidance on steam systems documents the multiple pathways through which steam boilers consume water that bypasses the sewer system entirely.
What Qualifies for Credits
The key qualification for any sewer credit is the same regardless of the source: you must be able to document the volume of water that doesn’t reach the sewer system. For boiler applications, the qualifying losses typically include steam vented to atmosphere (through safety valves, atmospheric vents, or process equipment), steam used for humidification that enters the air stream, condensate that isn’t returned to the boiler and doesn’t go to the sewer, and deaerator vent losses.
Boiler blowdown generally does NOT qualify for sewer credits because that water goes to the drain. However, the steam losses that blowdown replaces — the reason you need makeup water in the first place — do qualify. This distinction matters when you’re calculating your credit amount and presenting data to the utility.
Most utilities that offer sewer credits for cooling towers also accept boiler loss documentation. The application process is essentially the same — you need metering data that quantifies your non-sewer water consumption. A submeter on the boiler makeup water line, combined with metering on the condensate return (if applicable), gives you the data you need.
Combining Boiler and Cooling Tower Credits
Buildings that have both cooling towers and steam boilers are in the strongest position for sewer credits because they can combine both sources of non-sewer water loss into a single application. A hospital, for example, might evaporate 200,000 gallons per month through its cooling towers and lose another 50,000 gallons per month through its steam system — qualifying for credits on 250,000 gallons rather than just 200,000.
The EPA’s WaterSense program for commercial buildings recommends accounting for all non-sewer water uses when pursuing utility bill reductions, not just the single largest source.
When filing your sewer credit application, presenting both cooling tower and boiler data in a single package demonstrates thoroughness and makes a stronger case to the utility reviewer. It also means you’ll capture the full savings potential rather than leaving boiler-related credits on the table.
Common Boiler Systems That Qualify
Not every building with a boiler qualifies for meaningful credits. Small hot water boilers in closed-loop heating systems lose very little water — the same water circulates continuously, and makeup requirements are minimal. The buildings most likely to benefit are those with steam boilers (especially high-pressure industrial systems), buildings with once-through steam systems that don’t return condensate, facilities with steam-powered kitchen equipment (hospitals, universities, large hotels), and buildings that use steam for direct humidification.
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.
Don’t Leave Boiler Credits on the Table
If your building has a steam boiler system, it’s worth investigating whether the water losses qualify for sewer credits in your municipality. The documentation requirements are similar to cooling tower credits, the application process is the same, and the savings are just as real. Many facilities focus exclusively on cooling tower evaporation and miss the additional savings available from their boiler systems — savings that could add thousands of dollars per year to their bottom line.
