Yes. A urinal flush valve, or flushometer, needs a vacuum breaker, because the valve pipes clean water straight into the fixture. The 2024 IPC requires flushometer vacuum breakers to meet ASSE 1001 and to be accessible, and the vacuum breaker's critical level must sit at least 6 inches above the urinal's flood rim.
What does the code say?
Section 415.2 of the 2024 IPC covers flushometer valves for both urinals and toilets. It says: "Vacuum breakers on flushometer valves shall conform to the performance requirements of ASSE 1001 or CSA B64.1.1. Access shall be provided to vacuum breakers."
ASSE 1001 is the standard for pipe-applied atmospheric vacuum breakers. Chapter 6 confirms it: "Pipe-applied atmospheric-type vacuum breakers shall conform to ASSE 1001 or CSA B64.1.1." The IPC's backflow table lists that device for "High or low hazard" and "Backsiphonage only," which fits a flush valve. It protects against water being pulled backward, not pushed.
The same section sets other rules for the valve itself. Flushometer valves "shall be of the water-conservation type and shall not be used where the water pressure is lower than the minimum required for normal operation." Each valve "shall be provided with a means for regulating the flow through the valve," and "The trap seal to the fixture shall be automatically refilled after each flushing cycle."
### How high does the vacuum breaker have to be?
At least 6 inches above the urinal. Section 608.16.4 says "The critical level of the vacuum breaker shall be set not less than 6 inches (152 mm) above the flood level rim of the fixture or device." The critical level is the point marked on the device that sets its working height.
Manufacturers build the rule into their instructions. Zurn's flushometer manual warns installers: "DO NOT cut vacuum breaker tube shorter than 6" below the -C-L- indicator mark, as vacuum breaker must be 6" above the fixture." The "C-L" mark is that critical level. Cutting the flush tube too short to make a valve fit a low urinal is a common install mistake, and it defeats the protection.
Why does a urinal need backflow protection?
Because the flush connection runs into the fixture. A faucet discharges above a sink, so there's open air between the spout and the water. A flushometer's outlet connects to the urinal's spud and discharges inside the fixture, so there's no air gap. If the urinal drain is partly blocked and the bowl fills, the flush outlet can end up close to dirty water.
Now add a pressure drop. A water main break, a fire hydrant being opened nearby, or heavy demand in a large building can pull pressure down fast. Without a vacuum breaker, the flush valve could act like a straw. The vacuum breaker opens to the air when pressure drops and breaks the siphon.
That's the same logic the code applies to hose bibbs, which need their own vacuum breaker. Our page on hose bibb vacuum breakers covers that version.
How do you know a vacuum breaker is failing?
A few signs point to it. Most flush valves put the vacuum breaker just below the valve body, on the flush tube.
- Water spraying or dripping from the vacuum breaker area during or after a flush.
- Water on the wall or floor under the valve with no other leak in sight.
- A cracked or stiff rubber part inside when the vacuum breaker is taken apart.
Inside most models is a small rubber part. Zurn's parts list names a "Vacuum Breaker Duckbill," a "Vacuum Breaker Insert" and a "Vacuum Breaker Friction Washer," and sells a "Vacuum Breaker Repair Kit" to replace them. Mineral buildup from hard water can stiffen these parts over time, which matters in the Phoenix area.
If the urinal also keeps running, the problem is more likely the valve's diaphragm or piston than the vacuum breaker. Our guide to a flushometer that keeps running covers that repair.
Can you remove or bypass the vacuum breaker?
No. It's a required backflow device, and removing it leaves a cross-connection between the drinking water and a urinal. It also violates Section 415.2. If the vacuum breaker leaks, repair or replace it with the part made for that valve. Don't cap it, tape it or swap in a plain tube.
### What if the valve doesn't fit with the vacuum breaker in place?
Then the fixture and valve don't match, or the rough-in is wrong. Common causes include a urinal replaced with a lower model, or a valve set too low on the wall. The fix is to adjust the supply height or pick a valve and flush tube that keep the critical level at least 6 inches above the rim. A plumber can check the rough-in against the manufacturer's dimensions.
What else does a urinal flush valve need?
The water supply has to keep up. The IPC sets these minimums for a urinal flush valve:
| Requirement | Code value |
|---|---|
| Supply pipe size (Table 604.5) | 3/4 inch |
| Flow rate at the outlet (Table 604.3) | 12 gpm |
| Flow pressure at the outlet (Table 604.3) | 25 psi |
| Maximum water use (Table 604.4) | 1.0 gallon per flushing cycle (0.5 in Phoenix) |
The EPA notes that "the current federal standard for commercial urinals is 1.0 gallon per flush (gpf)," and that "WaterSense labeled flushing urinals use no more than 0.5 gpf." Phoenix goes further than the model code. Its amended Table 604.4(1) caps a urinal at 0.5 gallon per flushing cycle, and the 1.0 gallon limit applies only to listed exceptions, such as buildings over six stories or care facilities. Our page on low-flow fixture requirements in Arizona covers the state picture. A WaterSense flush valve still needs a vacuum breaker. Only a waterless urinal, which has no water supply, skips it. Our page on waterless vs flush urinals covers that choice, and our comparison of flushometer and tank toilets covers the same valves on water closets.
### Does a urinal vacuum breaker need annual testing?
Not the way a backflow assembly is. Section 312.11.2 of the IPC, as Phoenix adopted it, lists the devices that "shall be tested at the time of installation, immediately after repairs or relocation and at least annually": reduced pressure, double check, pressure vacuum breaker, reduced-pressure and double-check detector fire-protection assemblies, spill-resistant vacuum breaker assemblies, and hose connection backflow preventers. A pipe-applied atmospheric vacuum breaker on a flush valve isn't on that list. It's checked by looking at it and replaced when it fails. The testable devices on your property, such as the main backflow assembly or the one serving irrigation, are a separate matter. Our guide to commercial backflow testing requirements in Arizona explains which devices need a yearly test.
### Who should service it?
A facility's maintenance staff can often replace a vacuum breaker kit on the same valve model. When the issue is height, a new valve or a different fixture, bring in a licensed plumber, since that work changes the plumbing and may need a permit. Adding flush valve checks to a commercial plumbing maintenance plan catches leaks before they reach the floor.
HQ Plumbing & Air services and replaces urinal and toilet flush valves, vacuum breakers and restroom supply lines for businesses across the Phoenix area. We're licensed and insured, available 24/7, and every job starts with a free estimate and upfront pricing. See our commercial plumbing services.
A vacuum breaker is a small part with one job: keeping the urinal out of the drinking water.