Boiler Replacement & Repair in Mill Valley, CA
Hydronic specialists who work in Mill Valley's canyon homes, older cottages and mid-century houses every week. Honest repair-or-replace advice and a written estimate before any work starts.
Pick a time online. We'll confirm your visit. No heat right now? Call or text.
Why boiler work in Mill Valley is different
More than a quarter of Mill Valley homes were built before 1940, and the typical house dates to the late 1950s. A lot of them are older than the boilers people try to fit into them. That's why boiler work here takes more than dropping in a new box. Boiler and radiant heat systems are the work we do most in Mill Valley.
Cascade, Blithedale & Warner Canyon
Narrow winding roads, redwoods, and steep lots where the mechanical room might be a crawlspace or a closet under the stairs. On hillside lots with stair-only access, the new boiler goes up by hand. A wall-hung condensing boiler is often the practical choice here: lighter, smaller and easier to vent.
Older downtown & hillside homes
Converted and added onto over the decades. We regularly find original piping, newer radiant zones from remodels, and controls nobody has documented. Before we recommend a new boiler, we trace what's actually there.
Sycamore/Tamalpais Park, Scott Valley/Alto, Enchanted Knolls
More conventional lots and mechanical rooms. Often radiant floors with manifolds and mixing valves, and a boiler that also makes the home's hot water through an indirect tank.
Tam Valley, Homestead, Strawberry, Almonte & Alto
These have a Mill Valley mailing address but are unincorporated Marin County, so permits go through the County, not the City. We handle it either way and tell you which applies before we start.
The boilers we see most in Mill Valley: legacy Triangle Tube Prestige units, Navien combis and wall-hung boilers (NCB, NHB, NFC), and wall-hung condensing boilers from NTI and HTP, including Munchkins.
Signs your boiler needs attention
What Mill Valley homeowners tell us, and what it usually means.
One zone or room stays cold
Usually: a failed zone valve or actuator, a stuck circulator, or air trapped in the loop.
We test each zone, purge air, and replace the valve or pump.
Radiant floors take all day to warm
Usually: a mixing valve set wrong or failing, low flow, or outdoor reset not set up.
We check supply temps, rebuild or replace the mixing valve, and program the controls.
Pressure keeps dropping below ~12 PSI
Usually: a leak in the system or a failed expansion tank.
We pressure test, check the tank charge, and find the leak.
Relief valve dripping
Usually: over-pressure from a waterlogged expansion tank or a failing fill valve.
We replace the tank or fill valve before the relief valve gives out.
Banging, kettling or whistling
Usually: scale or debris in the heat exchanger, or poor flow.
We clean or flush the heat exchanger and correct pump sizing.
Error codes, lockouts, or a jumping gas bill
Usually: ignition, flame sensing, venting or condensate problems, or poor combustion tuning.
We diagnose the code and run a combustion analysis. See our Navien error code guide.
No heat in Mill Valley? Get on our schedule.
Repair or replace? Our honest take
We'd rather fix a boiler that has years left in it than sell you one you don't need.
Repair usually makes sense when…
- The boiler is under about 12–15 years old and the heat exchanger is sound
- The problem is a part: circulator, zone valve, igniter, flame sensor, expansion tank, fill valve
- Parts for your model are still available
Replacement usually makes sense when…
- The boiler is 15–20+ years old, or the heat exchanger is cracked or corroded
- You're making repeated service calls every winter
- It's an old cast-iron or atmospheric boiler serving low-temperature radiant floors
- It's a Triangle Tube. The company shut down in November 2025. There's no warranty support and parts are dwindling. Read our Triangle Tube guide.
Is gas being banned for boilers?
Not yet. Under the Bay Area Air District's Rule 9-6, the zero-emission requirement for home-sized gas boilers applies to units manufactured after January 1, 2031 under the current rule (a July 2026 draft amendment would push that to 2033). Existing boilers can keep running, and new high-efficiency gas boilers can still be installed today. Thinking about an air-to-water heat pump for your radiant system? We'll tell you honestly whether your home, floors and electrical panel are a fit.
What a boiler replacement looks like
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Site visit & load check
We look at the house, piping, zones and venting path. A boiler sized from the old nameplate is often oversized, and oversized boilers short-cycle.
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Written estimate
Clear options, typically a combi versus a boiler with an indirect water heater, priced in writing before any work starts.
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Permit
We pull it, through the City of Mill Valley or through Marin County for Tam Valley, Homestead, Strawberry, Almonte and Alto.
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Install in 1–2 days
Old boiler out, new boiler in, proper primary/secondary piping or a low-loss header, ECM circulators, and venting to spec. Condensate goes to an approved drain with a neutralizer.
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Startup & combustion analysis
We tune the burner, set up outdoor reset so the boiler runs only as hot as the weather needs, and balance the zones.
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Walkthrough
We show you the system, thermostats and zones, and what to watch for.
Typical published ranges. Access, venting and piping move the number. See all boiler pricing. Marin Water supplies soft water (about 3.5–6.5 grains per gallon), which means less scale on heat exchangers. We still check fill water and inhibitor treatment on every closed loop.
A recent Mill Valley boiler job
Navien NFC combi boiler replaces an aging tank-style boiler and separate water heater
We replaced both appliances with a single Navien NFC combi, plus a new ECM circulator and zone controls. The result: faster hot water, a much quieter mechanical space, and one appliance instead of two.
What our customers say
Rated 5.0 on Google across our San Rafael and Sausalito locations (340+ reviews). A few from heating customers:
“The pump for my radiant heating went out in the middle of winter… Local Plumbing came right away… got the job done that day, on time, on budget and very professional.”Jeff S. · Local Plumbing customer
“Had to replace a failing gas/solar/radiant/domestic do everything 120 gal hot water tank. The job was complicated and a couple plumbers didn't even submit bids. You want Local Plumbing because they know all things radiant.”Naomi K. · Local Plumbing customer
“They helped us with a client that had issues with a defective radiant heat and hot water system. They were extremely kind and professional with our client who was raving about the work they did.”Alana C. · Local Plumbing customer
Why Mill Valley homeowners call Local Plumbing
- Hydronic specialists, not generalists. We service NTI, Navien, Lochinvar, HTP, Viessmann, IBC, Laars and legacy Triangle Tube systems.
- Combustion analysis on every service, not just a visual check.
- Local. Our warehouse and training facility is in San Rafael, a short drive away.
- Licensed C-16 & C-36 contractor(Lic #1091739). Owner Conor Crawford was named PHCC California Young Entrepreneur of the Year in 2026.
- Upfront written pricing before any work starts.
- We service boilers we didn't install. Most of the ones we work on in Mill Valley were installed decades ago by someone else.
Keeping a newer boiler healthy? Here's why annual boiler and radiant maintenance matters in Mill Valley.
Mill Valley boiler FAQ
How much does boiler replacement cost in Mill Valley?
Most high-efficiency boiler replacements we do run $8,500–$15,000. Combi boilers run $11,000–$16,500, and a boiler with an indirect water heater runs $19,000–$29,000. Tight access, long vent runs and radiant piping changes are the biggest cost drivers in Mill Valley homes. You'll get a written estimate before any work starts.
Do I need a permit to replace a boiler in Mill Valley?
Yes. In the City of Mill Valley, replacing a boiler needs a mechanical/plumbing permit. If your address is in Tam Valley, Homestead, Strawberry, Almonte or Alto, it's unincorporated Marin County and the permit comes from the County. We handle it.
Can I still install a gas boiler in 2026?
Yes. The Bay Area Air District's zero-emission rule for home-sized gas boilers applies to units manufactured after January 1, 2031 under the current rule, and a proposed amendment would move it to 2033. Existing boilers aren't affected.
My boiler is a Triangle Tube. Should I replace it now?
Not necessarily today. But with the company closed and parts limited, we recommend an inspection and a plan, so a failure in the middle of winter doesn't leave you with no heat while you wait on parts.
How long does a boiler install take?
Usually 1–2 days on site. Canyon homes with stair-only access or complex radiant piping can take longer, and we'll tell you up front.
Do you repair radiant floor heating in Mill Valley too?
Yes: cold zones, manifolds, mixing valves, circulators, and slab-loop diagnostics with thermal imaging. See radiant heating repair.
We work throughout Mill Valley (Downtown, Cascade and Blithedale canyons, Sycamore Park, Alto, Enchanted Knolls, Homestead and Tam Valley) and nearby in Strawberry, Corte Madera, Larkspur, Sausalito and Tiburon. See our Mill Valley plumbing page and boiler repair.
No heat, or planning ahead?
Book a Mill Valley boiler visit online, or call or text us.
