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Building Code Reference

Got a CPC 603.0 correction?

Hose bibb vacuum breaker

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CPC 603.0 is the California Plumbing Code section that requires a vacuum breaker or listed backflow prevention device on every hose bibb — that’s any outdoor spigot or laundry bibb where a hose can be connected. The requirement exists because a hose submerged in a bucket, pool, or chemical sprayer can siphon contaminated water back into the potable supply if pressure drops. Most residential and ADU permits get flagged on 603.0 when the plumbing plans show hose bibbs without calling out the required backflow protection.

How to fix it

  1. Mark every hose bibb on the plumbing plan

    Go through the plumbing plan and fixture schedule and confirm every hose bibb is labeled. This includes outdoor hose connections at the front, side, and rear of the building, laundry room bibbs with hose-thread outlets, and any bibb feeding an irrigation zone. If a bibb appears in elevation or floor plan but not in the fixture schedule, add it. Plan-checkers work from the fixture schedule first — if the bibb isn’t listed there, the vacuum breaker won’t be either.

  2. Specify vacuum breaker type in the fixture schedule

    For each hose bibb, add a note identifying the backflow protection type. CPC 603.5.7 accepts a nonremovable hose bibb-type vacuum breaker (ASSE 1011), a nonremovable hose bibb-type backflow preventer (ASSE 1052), or an atmospheric vacuum breaker at least 6 inches above the highest point of use. The device may be integral to the bibb or threaded on, but it must be the nonremovable type. Spec it as ‘hose bibb with nonremovable ASSE 1011 vacuum breaker.’ Pick one and call it out on every bibb in the schedule.

  3. Add a plumbing note referencing CPC 603.0

    On the plumbing general notes sheet (or on the sheet where hose bibbs appear), add a note: ‘All hose bibbs to be provided with nonremovable vacuum breaker per CPC 603.5.7, ASSE 1011 or ASSE 1052 listed.’ This gives the plan-checker a code cross-reference and a spec standard in one line. Without it, the checker has to infer compliance from the fixture schedule alone, and that’s often what triggers the correction.

  4. Check laundry and utility bibbs

    Clothes washer connections, water heater drains, and boiler drains are exempt under CPC 603.5.7, but other indoor bibbs with hose-thread outlets fall under the same rule as outdoor bibbs. If the laundry room has a utility sink or other bibb with a hose thread, it needs a vacuum breaker callout. Some plans show the laundry bibb as part of the appliance connection detail rather than the plumbing fixture schedule, so it slips through. Check both locations.

  5. Verify irrigation tie-ins show backflow protection

    If any irrigation zone is connected through a hose bibb rather than a dedicated backflow preventer assembly, the plan needs to show backflow protection at that tie-in. A hose bibb vacuum breaker is not for use under continuous pressure or with a valve downstream, so it does not protect an irrigation manifold; CPC 603.5.6 calls for an AVB, PVB, SVB, or RP device. If the irrigation system has its own reduced-pressure backflow preventer (RPZ) or pressure vacuum breaker (PVB) assembly at the manifold, that serves as the protection device — but the plan must show it. Plans that show irrigation running from an unprotected bibb are a common secondary catch on plumbing corrections.

  6. Specify ASSE 1011 listing for add-on vacuum breakers

    If you’re using an add-on hose-end vacuum breaker, it must be listed to ASSE 1011. This is the standard for hose connection vacuum breakers. When you call it out on the plans, note ‘ASSE 1011 listed’ so the inspector can verify at the field inspection. Generic or unlisted devices won’t pass. Watts, Woodford, and Zurn all make ASSE 1011 listed hose-end vacuum breakers — confirm the product data sheet shows that listing before you spec it.

  7. Cross-check the full 603 series if your letter cites multiple subsections

    CPC 603.0 covers the hose bibb vacuum breaker requirement, but the broader 603 series (603.1 through 603.5) covers other backflow hazard categories. If your project has chemical injection systems, boiler fill connections, or fire sprinkler system tie-ins to the potable supply, those connections require a higher-degree backflow preventer. Hose bibbs are a low-hazard category, but if your plan-check letter cites 603.0 alongside 603.3 or 603.5, review each section separately and address them in distinct plan notes.

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Why you got flagged

Plan-checkers flag CPC 603.0 for one main reason: the hose bibbs are on the plans but the vacuum breaker isn’t. Here’s how that shows up in practice.

The most common correction is a simple sheet omission. The plumbing riser or fixture schedule lists the hose bibbs by location — front yard, side yard, laundry — but there’s no note on type. A plain hose bibb without a vacuum breaker label fails. The plan-checker circles it and writes “provide vacuum breaker per CPC 603.0.” To fix it, you add a callout or note on the plumbing plan specifying hose bibb with integral vacuum breaker, atmospheric-type, or a separate add-on vacuum breaker.

Integral vs. add-on confusion trips up a lot of plans. An integral vacuum breaker is built into the hose bibb body itself; an add-on sits at the outlet. Either satisfies 603.0, but the plan needs to show which one. If the fixture schedule just says “hose bibb — as specified,” with no spec sheet attached, that’s a correction.

Laundry bibbs get overlooked because they’re indoors. CPC 603.5.7 applies to any outlet with a hose attachment except clothes washer connections, water heater drains, and boiler drains, so a laundry sink bibb with a hose thread still needs one. Plans that show a laundry bibb without vacuum breaker notation get flagged the same as outdoor bibbs.

Irrigation connections also draw corrections when they’re served off a hose bibb rather than a dedicated backflow preventer. If the plans route irrigation from a hose bibb, the plan-checker will verify backflow protection is shown at that connection point.

The official code

California Plumbing Code — Building Standards Commission, Part 5

Read the source →

Common questions

Does CPC 603.0 apply to ADUs?
Yes. CPC 603.0 applies to any new residential construction, addition, or alteration that includes hose bibbs, regardless of whether it’s a main dwelling unit or an ADU. ADU permits frequently get flagged on 603.0 because the plumbing plans are drawn quickly and the vacuum breaker callout gets left off. If you’re pulling an ADU permit, check your plumbing plan for every bibb before you submit.
Does a washing machine connection need a vacuum breaker under 603.0?
It depends on the outlet type. A standard washing machine supply valve with a compression or push-fit connection to a braided hose does not typically require a vacuum breaker under 603.0 — the supply valve and hose assembly handle that. But if there’s a laundry bibb with an exposed hose-thread outlet (the kind you could screw a garden hose onto), that bibb needs a vacuum breaker. Check whether the connection has hose threads. If it does, add the callout.
What's the difference between a vacuum breaker and a backflow preventer?
A vacuum breaker is one type of backflow preventer. The term ‘backflow preventer’ is the broader category, and it includes hose connection vacuum breakers (the usual choice at hose bibbs), reduced-pressure principle assemblies (RPZ), pressure vacuum breakers (PVB), and double-check valve assemblies. The degree of protection required depends on the hazard category. Hose bibbs are a low-to-medium hazard — they can be submerged in potentially contaminated water — so a nonremovable hose connection vacuum breaker listed to ASSE 1011 is sufficient. Higher-hazard connections like chemical feeds or irrigation systems with fertilizer injection require RPZ or PVB assemblies.
Can I install the vacuum breaker after rough-in and still pass inspection?
Yes for the field inspection, but your plans need to show it before plan check approval. The plans are what get you the permit. Field inspection is when the inspector verifies what was shown on the approved plans is actually installed. So the sequence is: get the vacuum breaker callout on your plans, get plan check approval, rough in the bibb, install the vacuum breaker at or before the plumbing rough-in inspection, and confirm it’s there at final. If you install the bibb at rough-in without the vacuum breaker and the inspector catches it, you’ll get a correction notice that delays your final.
Does a frost-free hose bibb satisfy CPC 603.0 on its own?
A frost-free (anti-siphon) hose bibb typically has an integral atmospheric vacuum breaker built in, which does satisfy 603.0 — but only if the product is ASSE 1011 listed. Frost-free means the valve seat is located inside the wall to prevent freezing, while the anti-siphon portion handles backflow. Confirm that the specific product you’re specifying is listed to ASSE 1011 and note that on the fixture schedule. A frost-free bibb without ASSE 1011 listing doesn’t meet the standard.
What happens if I miss the vacuum breaker callout and it’s caught at rough-in inspection?
You get a correction notice from the inspector, and they won’t sign off on rough-in until the vacuum breaker is installed. The good news is this is usually a quick fix in the field — you can thread an ASSE 1011 hose-end vacuum breaker onto the bibb outlet and have the inspector re-check. The delay is typically a few days for a re-inspection, not a full plan revision cycle. If the same oversight is on multiple bibbs, fix them all before calling for re-inspection.

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