Waterless and Low-Flow Urinals Explained

The water savings on a waterless urinal are real and easy to calculate. The maintenance bill is the part nobody hands you up front, and it is the number that decides whether the fixture is right for your building. A waterless urinal uses no flush water at all. A low-flow, or high-efficiency, urinal still flushes but with a fraction of the water an older fixture used. Both cut consumption, but they do it in completely different ways, and they ask different things of your facilities staff and your local code official in return. This guide separates the two so you can weigh water savings against upkeep and acceptance before you specify either one.

A few neighboring topics live in their own guides so this one can stay on how waterless and low-flow urinals work and how to choose. For the manual flushometer valve that flushes a conventional urinal, see our guide on how a commercial flushometer works (237). For touchless sensor flush technology on flushed urinals, see our guide on how sensor and touchless plumbing controls work (239). For diagnosing a urinal that runs or leaks, see our guide on why commercial faucets and toilets run or leak (238). For how many urinals a building needs by occupancy, see our guide on how many restroom fixtures a commercial building needs (242). For ADA rim-height and clearance specifics, see our guide on what makes a commercial restroom ADA-compliant (240).

How a Waterless Urinal Drains and Blocks Sewer Gas Without a Flush

A waterless urinal works because a lighter-than-water sealant lets liquid pass down the drain while floating back into place to block sewer gas. There is no flush valve, no supply line to the bowl, and no stored water. Urine simply runs down the sloped fixture surface and into the drain, where the trapping device does the job a water-filled trap does on a conventional fixture.

The barrier is the whole trick. Most waterless urinals use an oily sealant liquid that is less dense than urine. Urine, being mostly water, sinks through the lighter sealant and continues down to the building’s drain line. The sealant then re-forms a continuous layer on top. That floating layer is what stops sewer gas from rising back into the restroom, the same protective job that the water sitting in a P-trap does on a standard fixture. Under the relevant national fixture standard for these products, ASME A112.19.19, a nonwater urinal must provide a trap seal that complies with the plumbing code and use a liquid barrier sealant to maintain that seal.

Two practical points follow from this design. First, a waterless urinal still needs a real drain connection and venting, just like any fixture; “waterless” refers to the flush, not to the plumbing behind the wall. Second, the seal depends entirely on the sealant and the trapping device being intact. If the sealant is depleted, displaced, or rinsed away, the sewer-gas barrier is gone until it is restored. That dependency is the root of every maintenance consideration later in this guide.

Sealant-Liquid vs. Mechanical-Trap Cartridge Designs

Waterless urinals split into two families: those that use a replaceable cartridge holding sealant liquid, and those that use a mechanical one-way trap insert. Both sit in the drain and both block sewer gas, but they are serviced differently and are not treated identically by every code authority.

A sealant-liquid cartridge is a removable insert that holds the oily barrier fluid and channels drainage through it. As the fixture is used, small amounts of sealant gradually wash down the drain and have to be replenished, and the cartridge itself is replaced on a schedule. The barrier here is the liquid, so the maintenance task is keeping that liquid topped up and swapping the cartridge before it fouls.

A mechanical-trap design replaces the liquid with a physical one-way device, often a flexible silicone diaphragm or a hinged flap, that opens to let liquid pass and closes to seal against gas. Some of these use little or no sealant liquid. The appeal is fewer fluid top-ups; the tradeoff is a moving or flexing part that can stiffen, scale over, or clog and then has to be cleaned or replaced.

Code acceptance is where the distinction stops being academic. Some jurisdictions treat the two designs differently, and at least one state has specifically prohibited mechanical trap inserts on urinals while still permitting other approaches. Manufacturer literature from the major fixture brands describes the exact cartridge or insert their model uses and the service interval it is rated for, and those vary by product. The point to carry forward is that the trapping method you choose affects both your maintenance routine and whether your local authority will sign off on it.

Low-Flow (Pint and Sub-Pint) Urinals: How They Cut Water Use

A low-flow urinal flushes with far less water than the old standard, and the common “pint” label tells you roughly how much. The current federal maximum for urinals is 1.0 gallon per flush under the Energy Policy Act of 1992. A high-efficiency urinal is defined as one that uses 0.5 gpf or less, which is half the federal standard, and that 0.5 gpf threshold is also the maximum for a urinal to earn the EPA WaterSense label.

The terminology comes straight from the flush volume. A “pint” urinal flushes with about one pint of water, which is 0.125 gallon per flush. Manufacturers also offer sub-pint and intermediate volumes such as 0.25 gpf. Because a true pint flush uses one-eighth of a gallon against the 1.0 gpf federal ceiling, these fixtures can cut urinal water use dramatically compared with an older model, while still using a flush to carry waste away and rinse the bowl.

Unlike a waterless fixture, a low-flow urinal keeps a conventional water-filled trap and a flush valve. That means it behaves like a normal flushed urinal in every way except volume: the trap seal is maintained by water, sewer gas is blocked by water, and there is no sealant to manage. The flush still arrives from the building’s pressurized supply through a flushometer valve, which is covered in its own guide noted above. The water savings are smaller per fixture than going fully waterless, but the upkeep is also closer to what your staff already knows.

EPA estimates give a sense of scale. The agency reports that replacing a single older 1.5 gpf urinal with a WaterSense labeled model can save more than 4,600 gallons of water per year, and that a typical office building can cut urinal water use by 26,000 gallons per year or more. Those figures are for labeled flushing urinals, not waterless models, which save the flush water entirely but carry the maintenance profile described next.

The Maintenance Tradeoff: Cartridges, Cleaning, and Drain-Line Scale

The honest decision driver for waterless urinals is maintenance, not water savings. The savings are predictable; the upkeep is where buildings get surprised. Three things have to be managed, and skipping any of them is what turns a money-saving fixture into a complaint.

The first is the trap itself. Sealant-liquid cartridges need periodic top-ups of sealant and scheduled cartridge replacement, on an interval that manufacturers publish for each model and that depends heavily on traffic. A urinal in a busy stadium concourse cycles its sealant far faster than one in a small office. Mechanical inserts skip the liquid but still need cleaning and eventual replacement. Either way, a waterless fixture is not a “install and forget” item; it trades a water bill for a consumables-and-labor schedule.

The second is the drain line. Without a flush of water rinsing the trapway and branch line, mineral and uric deposits can build up inside the pipe over time and narrow it, especially where a waterless fixture ties into older drainage. This is the real-world issue that vendor-driven “just go waterless” articles tend to skip. It is managed with the right cleaning routine and periodic drain maintenance, but it is a routine that has to actually happen.

The third is daily cleaning technique. Cleaning a waterless urinal is not the same as cleaning a flushed one. Custodial staff generally should not pour buckets of water or harsh cleaners down the fixture, because flooding the drain can wash out the sealant or disturb the trap and let sewer gas through until it re-seals. Staff training is part of the install, not an afterthought.

One firm line: modifying the drain line, changing venting, or rerouting waste piping to accommodate a urinal retrofit is not facilities-staff or do-it-yourself work. That is a job for a licensed commercial plumber working to the locally adopted code. The same is true for the conventional flushometer valve on a low-flow urinal if it needs internal repair. Routine sealant top-ups, cartridge swaps, and surface cleaning are facility tasks; anything behind the wall is not.

Deciding Between Waterless and Low-Flow: Code Acceptance and Total Cost

The choice comes down to two questions: will your jurisdiction accept the fixture, and does the total cost of ownership beat the water it saves. Water savings alone rarely settle it, because the upkeep and code factors can swing the answer either direction.

Start with code acceptance, because it can end the conversation before cost matters. Acceptance of waterless urinals genuinely varies by jurisdiction. Some authorities allow them outright, some allow them only under specific conditions, and some restrict particular designs. Common code conditions, where waterless urinals are permitted, can include conformance to the ASME A112.19.19 nonwater urinal standard, a trap seal that meets the plumbing code, proper venting, and in some adopted codes a requirement to rough in a water supply at the fixture so a conventional urinal can be installed later. At least one state has prohibited mechanical trap inserts on urinals. None of that is uniform, which is exactly why you confirm acceptance with your local building department and a licensed plumbing designer before you specify, rather than assuming the model on the cut sheet is allowed where you build. Specific section numbers and conditions differ by the code edition your jurisdiction has adopted.

Then weigh total cost honestly. A waterless fixture removes the flush water entirely, which is the largest savings, but adds sealant, cartridges or inserts, drain-line maintenance, and staff training to the ledger. A low-flow or pint urinal saves less water per flush but keeps a familiar water trap, no sealant, and a maintenance routine your team already runs. For a high-traffic building where water is expensive and a facilities crew is already on site, waterless can pencil out well. For a building with light traffic, limited custodial coverage, or a code authority that restricts waterless designs, a high-efficiency flushing urinal often wins. Match the fixture to the building you actually operate, not to the water-savings figure alone.

Frequently Asked Questions

Do waterless urinals smell worse than flushed ones?
Not when the sealant and trap are maintained. The floating sealant layer blocks sewer gas as effectively as a water trap, so a properly serviced waterless urinal should not smell. Odor usually means the sealant has been depleted, washed out by improper cleaning, or the cartridge is overdue for service. The smell is a maintenance signal, not an inherent flaw of the design.

How often does a waterless urinal cartridge need to be replaced?
It depends on traffic and the specific model, so the right interval is the one the manufacturer publishes for the cartridge you install, adjusted for how heavily the fixture is used. A busy public restroom cycles through sealant and cartridges far faster than a low-use office. Plan around the manufacturer’s rated service interval and your own traffic, not a single fixed number.

What does “pint” mean on a low-flow urinal?
It refers to the flush volume. A pint urinal flushes with about one pint of water, which is 0.125 gallon per flush. For comparison, the federal maximum for urinals is 1.0 gallon per flush, and a high-efficiency urinal uses 0.5 gallon per flush or less. So a pint model uses a fraction of the older standard while still flushing.

Are waterless urinals allowed by code everywhere?
No. Acceptance varies by jurisdiction. Some local authorities permit waterless urinals, sometimes only under specific conditions such as conformance to the ASME A112.19.19 standard and particular trap, vent, and rough-in rules, and some restrict certain designs. Always confirm acceptance with your local building department and a licensed plumbing designer before specifying one.

Which saves more water, waterless or low-flow?
A waterless urinal saves the most water because it uses no flush water at all, while a low-flow urinal still flushes with a small metered volume. The catch is that the larger water savings of a waterless fixture come with added sealant, cartridge, and drain-maintenance costs, so the better total value depends on your building’s traffic, labor coverage, and what your code authority allows.

This article is general information, not professional advice. Plumbing code acceptance and fixture requirements vary by jurisdiction, and any drain, vent, or supply work is for a licensed commercial plumber and your local building authority; confirm acceptance and final requirements with your local building department before specifying a fixture.

Sources

• U.S. EPA, WaterSense, Urinals (federal standard 1.0 gpf, WaterSense maximum 0.5 gpf, water-savings estimates): https://www.epa.gov/watersense/urinals
• U.S. EPA, WaterSense, Commercial Toilets and water-efficient fixture program context: https://www.epa.gov/watersense/commercial-toilets
• ASME, A112.19.19 Vitreous China Nonwater Urinals (nonwater urinal standard, trap seal and liquid barrier sealant requirements): https://www.asme.org/codes-standards/find-codes-standards/vitreous-china-nonwater-urinals
• International Code Council, 2021 International Plumbing Code, Chapter 4: Fixtures, Faucets and Fixture Fittings (urinal and nonwater urinal provisions; sections and adoption vary by jurisdiction): https://codes.iccsafe.org/content/IPC2021P1/chapter-4-fixtures-faucets-and-fixture-fittings
• UpCodes, Non-Water Using Urinals (code requirements: ASME A112.19.19 conformance, trap seal, venting, and water-supply rough-in; jurisdiction-dependent): https://up.codes/s/non-water-using-urinals