Water heaters Mountain View

Fixing a Mountain View water heater, or knowing when it is done

Many Mountain View water heater calls turn out to be parts, not tanks: a relief valve dripping from high pressure or a missing expansion tank, a pilot that will not stay lit, a flame arrestor clogged with lint. A tank leaking from its shell, or one that has sat in floodwater, means replacement, and every replacement needs a city permit. Under the codes in force since January 1, 2026, a new gas heater comes with a 240-volt circuit pre-wired for a future heat pump.

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  • Rules on this page checked against 16 public sources, October 2026
Mountain View City Hall
Mountain View City Hall. Photo: Aleh Haiko, CC BY-SA 3.0, via Wikimedia Commons.

How water heater work goes in Mountain View

Mountain View rules a repair can turn into

  1. Water Heater Replacement and Tankless Water Heater Guide

    The Building Division's guide for one- and two-family homes requires a permit for every water heater installation and replacement, obtained before work starts, asks for an HOA authorization letter where an association oversees the property, and sends exterior changes to Planning first. For tankless units it warns that they draw far more gas than a tank, so house gas piping may need resizing, that they may need a 120-volt receptacle for their controls, and that PG&E wants 36 inches of horizontal clearance from a gas meter on the same wall.

    Source: City of Mountain View Building Division (mountainview.gov)

  2. Online permits for replacements

    On a residential lot, the city issues a water heater replacement permit online when a gas or electric unit of 30 to 150 gallons goes where the old one stood; a new location needs the regular process. The relief valve drain keeps the valve's full opening, generally 3/4 inch, to its end, and the Chief Building Official may approve a laundry tub, floor sink or floor drain instead of the exterior. A heat pump replacement also needs a disconnect within sight of the unit and a receptacle within 25 feet.

    Source: City of Mountain View Building Division (developmentpermits.mountainview.gov)

  3. Go Electric: gas replacements and second heaters

    The Building Division's Go Electric page answers the question directly: the city does not require a gas water heater to be replaced with a heat pump. A like-for-like gas replacement is permitted with pre-wiring for a future heat pump water heater, meaning a dedicated 240-volt circuit with conductors for at least 30 amps, and a second water heater added where none existed must be a heat pump. The page recommends the outlet within 3 feet of the heater, and a 240-volt circuit for four or more occupants or three or more bedrooms.

    Source: City of Mountain View (developmentpermits.mountainview.gov)

  4. Rule 9-6 and mobile home water heaters

    The Air District's September 2026 myths-and-facts sheet states that mobile home water heaters and furnaces are exempt from the zero-NOx requirements of Rules 9-4 and 9-6. Its October 2026 staff report proposes Section 9-6-116 to spell this out: such heaters stay under the older 40 nanograms per joule standard, are sold as their own equipment class and need no exemption form. For a site-built house, a small gas heater manufactured after the compliance date, January 1, 2027 in the adopted rule, must emit zero NOx.

    Source: Bay Area Air District (baaqmd.gov)

State license for this work: C-36 Plumbing, C-20 Warm-Air Heating, Ventilating and Air-Conditioning, C-10 Electrical. Look up a contractor's license on the CSLB website (cslb.ca.gov).

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Free to request, and you agree the scope and price with the person you hire before work starts. In California, a job over $1,000 in labor and materials, or one that needs a building permit, must be done by a contractor licensed by the CSLB in the right class. Ask for the license number and check it at cslb.ca.gov.

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The work

Symptoms that bring a plumber, and what usually fixes them

  • A relief valve that drips or spits

    A.O. Smith's use and care guide says a dripping temperature and pressure relief valve is usually caused by water pressure that is too high or by a missing thermal expansion tank, and its service handbook warns against relying on the valve to absorb thermal expansion, since it is an emergency device. The usual remedy is a pressure reducing valve set around 50 to 60 psi and a properly sized expansion tank, not a new heater. Mountain View wants the valve's drain run outside, pointing down, 6 to 24 inches above the ground.

  • A pilot that goes out, or no hot water at all

    On a standard flammable-vapor-resistant gas tank, A.O. Smith's handbook traces a pilot that will not stay lit to the thermocouple or the gas control valve, both replaceable parts, and a heater that keeps shutting itself down to too little combustion air, often a base-ring filter or flame arrestor clogged with dust or lint. It calls for checking that filter at least once a year, and more often where lint and dirt collect. In a Mountain View closet, the two 100-square-inch air openings the city requires have to stay clear as well.

  • Rumbling, rusty water, a wet floor

    The city's Water Heater Forward page lists the warning signs: no hot water, leaking, corrosion in or around the unit, rumbling or vibration, and rust in the water, and it says a heater 10 or more years old most likely needs replacing. Before condemning a tank, A.O. Smith's leakage checklist rules out condensation, which is common at startup and when the incoming water is cold, and leaks at the drain valve, the anode fitting or the relief valve fitting. Water seeping from the tank shell itself is the sign that points to a new heater.

  • A heater that sat in floodwater

    A.O. Smith's manuals are blunt: if any part of a gas water heater has been under water, do not use it or try to repair it, because the entire unit has to be replaced. Mountain View's flood page advises elevating or relocating water heaters that sit where flooding is likely, and the city's water heater guide requires appliances in flood zones to be elevated at or above the flood elevation. The replacement goes in on a permit like any other.

  • A heat pump unit running on its backup

    Heat pump water heaters have their own upkeep. Silicon Valley Clean Energy, the electricity provider most Mountain View homes use, tells owners to inspect the air filter every season and to keep the unit in heat pump mode, since the electric heater setting uses the most energy, moving to hybrid on heavy-use days and to vacation mode for long trips. A replacement heat pump in the same spot can be permitted online if it sits in a garage or enclosed storage area and stays within the house's existing electrical capacity.

Two wall-mounted tankless water heaters plumbed with copper supply lines
Two wall-mounted tankless water heaters plumbed with copper supply lines. Photo: Behrat, CC BY-SA 3.0, via Wikimedia Commons.

The houses here

Garages, closets, park homes and townhouse complexes

Many of Mountain View's single-family streets are tracts from the 1950s, the decade its population climbed from 6,563 to 30,889, and their water heaters mostly answer to a garage rule or a closet rule. In a garage, the pilot and controls sit at least 18 inches above the floor, and where a car could hit the unit the city's guide shows a 4-inch steel pipe filled with concrete, set in a 12-inch footing 3 feet deep and standing 2 feet 9 inches above the floor. In a closet, combustion air comes through two openings of 100 square inches each, one within 12 inches of the top and one within 12 inches of the bottom. Townhouse complexes add a step: the Building Division wants a letter of authorization signed by the HOA. The city's mobile home parks fall under a different air rule altogether.

Part by part

Two parts of Mountain View where the answer changes

  • The mobile home parks

    A manufactured home in one of Mountain View's parks takes a mobile home water heater, an equipment class the Air District leaves out of its zero-NOx standard, so a gas replacement there is not caught by the 2027 date. Silicon Valley Clean Energy's rebates still cover mobile and manufactured homes for an owner who would rather switch to a heat pump. Check with the park office before any work outside the home.

  • Along Permanente Creek

    The city traces flooding in its special flood hazard areas to Bay tides and Permanente Creek. Valley Water's completed creek project and revised FEMA maps, in effect since September 5, 2024, moved many properties from the 100-year floodplain into lower-risk Zone X. For a house still mapped in a flood zone, the city's water heater guide requires the heater to sit at or above the flood elevation.

Before you hire

Before a Mountain View plumber quotes a new heater

  • Can you tell whether the leak is the tank itself or a fitting, drain valve or relief valve that could be replaced instead?
  • Will you check our water pressure and look for a missing expansion tank before replacing a dripping relief valve?
  • For a gas-for-gas replacement, does the quote include the 240-volt, 30-amp pre-wiring the city asks for?
  • For a tankless unit on an outside wall, will it clear the gas meter by 36 inches, and is our gas line large enough?
  • Is your C-36 Plumbing license current on cslb.ca.gov, and will you pull the Mountain View permit before starting?

Free, no obligation. Next, add your details in the request form.

Questions

Mountain View water heater questions, from relief valves to floods

Our relief valve drips after hot showers. Does the Mountain View water heater need replacing?

Probably not. A.O. Smith's service handbook lists thermal expansion as a common cause: in a closed system with a check valve, pressure reducing valve or backflow preventer, heated water has nowhere to go, and the valve drips while the heater recovers. Its remedy is a pressure reducing valve with a properly sized expansion tank. A valve that has dripped for a long time should also be inspected for mineral buildup.

Can a gas water heater in Mountain View be replaced with another gas one?

Yes. The city's Go Electric page says a like-for-like gas replacement is allowed with pre-wiring for a future heat pump water heater, a dedicated 240-volt circuit with conductors rated for at least 30 amps. What changes is supply: under the Air District's adopted rule, small gas heaters manufactured after January 1, 2027 must meet a zero-NOx standard, and its Board considers moving that date to 2028 on November 4, 2026.

Our mobile home's water heater failed. Does the Air District rule stop a gas replacement?

No. The Air District states that mobile home water heaters are exempt from its zero-NOx requirements, and its proposed amendments add a section confirming that no exemption form is needed. Because they are sold as their own equipment class, ask for a heater made for mobile homes rather than a standard residential tank.

The garage flooded in a storm. Can the water heater be dried out and relit?

No. A.O. Smith's guides say that if any part of the water heater has been under water, it must not be used or repaired, and the whole unit is replaced by a qualified installer. If the house is in a mapped flood zone, the replacement has to sit at or above the flood elevation under the city's water heater guide, which is worth settling before the new unit is ordered.

Is there a Mountain View rebate for switching to a heat pump water heater?

Yes, for now. Mountain View's Water Heater Forward program pairs a city rebate with Silicon Valley Clean Energy's, administered by SVCE, and one application on SVCE's rebate site applies for both. The city describes it as limited-time, and SVCE asks for the reservation before the heater is installed, with emergency replacements flagged on the application.

How old is too old for a water heater in Mountain View?

The city's Water Heater Forward page says a heater 10 or more years old most likely needs replacing, and Silicon Valley Clean Energy says it is cheaper and easier to replace one before it breaks, around the 8- to 12-year mark. Age is a guide, not a verdict: a younger tank leaking from its shell is finished, while an older one with a dripping relief valve may only need pressure control.

Where these facts come from

Checked against these public sources in October 2026. Rules and programs change: confirm permit requirements with the city before work starts, and a contractor's license on the CSLB website.

  • mountainview.gov: 638236402467770000 (mountainview.gov)
  • developmentpermits.mountainview.gov: same day permits (developmentpermits.mountainview.gov)
  • developmentpermits.mountainview.gov: going electric (developmentpermits.mountainview.gov)
  • developmentpermits.mountainview.gov: green building and reach codes (developmentpermits.mountainview.gov)
  • mountainview.gov: water heater (mountainview.gov)
  • mountainview.gov: flood protection (mountainview.gov)
  • valleywater.org: permanente creek flood protection
  • baaqmd.gov: 20260901 appliance rules myths vs facts 8312026r pdf (baaqmd.gov)
  • baaqmd.gov: 20261002 staff report rule 9 6 pdf (baaqmd.gov)
  • baaqmd.gov: building appliances (baaqmd.gov)
  • assets.aosmith.com: 100283020
  • assets.aosmith.com: 316877 000

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