A home inspector walks into the garage before a sale, looks at the water heater, and writes it up. The tank has two straps on it. The seller is baffled — the plumber who installed it put those straps on himself. The problem is where they sit: both wrapped around the middle of the tank, a hand's width apart. California's plumbing code does not just ask for straps. It says which parts of the tank they have to be around.
The short answer: water heaters must be anchored or strapped to resist horizontal displacement due to earthquake motion, with strapping at points within the upper one-third and the lower one-third of the tank's vertical dimension — and at the lower point, a distance of not less than 4 inches must be maintained above the controls (§ 507.2).
Key numbers
| Rule | Requirement | Where it comes from |
|---|---|---|
| Upper strap location | Within the upper one-third of the tank's vertical dimension | § 507.2 |
| Lower strap location | Within the lower one-third of the tank's vertical dimension | § 507.2 |
| Clearance above the controls | Not less than 4 inches at the lower strap | § 507.2 |
| Who it applies to | All new and replacement water heaters, and all existing residential water heaters | § 507.2 |
The rule, in one sentence
Water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion.
Everything else in this section is about doing that well. A tall cylinder full of water is close to top-heavy, and the failure mode in an earthquake is not the tank exploding — it is the tank walking sideways off its stand and tearing its own gas line or water connections loose. That is why the code cares so much about where the restraint is rather than how much of it there is.
Two zones, not two random heights. The strapping goes at points within the upper third and within the lower third of the tank's vertical dimension (§ 507.2). Restraint near the top stops the tank from tipping; restraint near the bottom stops it from sliding. Two straps side by side in the middle of the tank do neither job well, which is the most common failure a home inspector writes up.
Four inches above the controls. At the lower point, the code requires not less than 4 inches of distance to be maintained above the controls. On a gas heater, the controls are the thermostat and gas valve assembly at the bottom of the tank. A strap crossing directly over that assembly can foul the gas control, block access, or interfere with servicing — and in a quake, a strap bearing on the valve body is a leak waiting to happen.
It applies to the heater you already own
Most plumbing-code requirements attach to new work. This one does not, and the code says so directly. Section 507.2 reproduces the relevant part of Health and Safety Code section 19211(a) for clarity, and that statute reaches further than the installation itself: all new and replacement water heaters, and all existing residential water heaters shall be braced, anchored or strapped to resist falling or horizontal displacement due to earthquake motion (§ 507.2).
At a minimum, any water heater is to be secured in accordance with the California Plumbing Code, or with modifications a city, county, or city and county has adopted for it. So the twenty-year-old heater in your garage is covered by this rule today, even though nobody is pulling a permit on it — which is exactly why it turns up in pre-sale inspection reports so often, and why it is one of the cheapest items on any such report to clear.
The other installation rules in this chapter
Four more requirements in the code apply to how a water heater is put in and left behind:
- Follow the manufacturer, and leave the paperwork. The installer must conform to the appliance and equipment manufacturers' recommendations in completing the installation, and must leave the installation, operating and maintenance instructions on the premises (§ 507.23). If your installer took the manual away, that is a code item, not just an annoyance — and those instructions are what the next plumber will need.
- Nothing bolted on that affects combustion. No device or attachment may be installed on any appliance that could in any way impair the combustion of gas (§ 507.17). Aftermarket add-ons around a gas burner are held to that standard.
- Piping must not be strained. Piping connected to a plumbing system must be installed so it is not subject to undue strains or stresses, with provision made for expansion, contraction and structural settlement. Plumbing piping may not be directly embedded in concrete or masonry, and no structural member may be seriously weakened or impaired by cutting or notching (§ 312.2). This is why flexible connectors are used at the tank: rigid pipe that cannot move is pipe that shears.
- Energy requirements are a separate rulebook. The plumbing code points at the California Energy Code for additional mandatory requirements for service water heating systems, including residential-specific ones (§ 501.2). Insulation, controls and efficiency for a replacement heater come from there, not from the plumbing chapter — one reason a like-for-like swap can still trigger requirements a homeowner did not expect.
What this article does not cover
The sections above are the appliance and equipment installation requirements (§ 507.0) that speak to strapping and installation practice. They are not the whole water heater chapter. Venting, combustion air, temperature and pressure relief valve discharge, drain pans, and clearances to combustibles are governed by their own sections, and this article does not state requirements for them — if you are planning a replacement, read the chapter, or ask your building department for the checklist they inspect against. Electrical connections for an electric or heat-pump heater are a permit-level matter for your electrician and the local inspector.
These are 2025 California code requirements, in effect statewide since January 1, 2026. They are minimums: cities and counties adopt the state code and may amend it, and the statute quoted above expressly contemplates local modifications. Water heater replacement is permitted work in most California jurisdictions, and the permit is what gets an inspector to confirm the straps are in the right two-thirds of the tank.
Sources
- § 507.2 — Seismic provisions for water heaters (California Plumbing Code)
- § 507.0 — Appliance and equipment installation requirements (California Plumbing Code)
- § 507.23 — Installation instructions (California Plumbing Code)
- § 507.17 — Extra device or attachment (California Plumbing Code)
- § 501.2 — Energy Code water heating requirements (California Plumbing Code)
- § 312.2 — Piping installation (California Plumbing Code)
