Boiler & Radiant Floor Heating in San Rafael
Most of the hydronic heat we work on in San Rafael runs through tubing in the floor, not through radiators. We replace the boilers that feed those floors, sort out zones, manifolds and mixing valves, and find leaks in the tubing. Our warehouse is on Andersen Drive, a few minutes from most San Rafael homes.
Book a visit online and we'll confirm the time. Floors cold tonight? Call or text.
In San Rafael, hydronic heat usually means a radiant floor
When we open up a heating system in San Rafael, it's far more often tubing in a slab or under a subfloor than a row of cast-iron radiators. A radiant floor wants cool, steady water, careful zoning and a tight system, and the boiler has to be chosen and piped for that.
Live in an Eichler in Terra Linda, Lucas Valley or Marinwood? Those slabs have their own history and leak patterns. See our Eichler radiant heat page. This page covers the rest of San Rafael.
Dominican & Sun Valley
The neighborhoods north and northwest of downtown, around the school that became Dominican University (it arrived in 1889) and up into Sun Valley, where most homes went up between 1940 and 1969. Expect anything from a Tudor Revival to a mid-century or newer custom house. Our five-zone Lochinvar Knight job below was here: a radiant system big enough that piping and zoning mattered as much as the boiler.
Across the rest of town
The typical San Rafael home dates to the late 1960s. In Glenwood, Peacock Gap, Bret Harte and the West End, radiant tubing turns up in slabs, in additions and under remodeled floors. Each era used different tubing and controls, so we identify what's in the floor before we quote anything.
Santa Venetia
The Santa Venetia flatlands sit in a Marin County flood control zone. If floodwater has ever reached a boiler's gas valve, that valve is replaced before the boiler fires again, even if it seems to work.
Gerstle Park & downtown
San Rafael's oldest neighborhood, first laid out as Short's Tract. This is where we still find cast-iron radiators, sometimes next to a newer radiant zone in a remodeled kitchen or bath. Radiator systems have their own section further down.
Where San Rafael radiant floors go wrong
A radiant floor has five working parts: the boiler, the mixing or temperature control, the circulators, the manifold, and the tubing. When a floor is cold, we test each one in that order rather than guessing.
Pressure falls a little every week
Water is leaving the system somewhere. It can be a weeping relief valve or a manifold fitting, but a slow, steady loss with nothing visible points to the tubing in the floor.
We isolate the boiler side first, then pressure-test each loop at the manifold to find the one that won't hold.
Floor is lukewarm while the boiler runs hot
The mixing valve that tempers boiler water down to floor temperature is stuck, fouled inside, or set wrong.
We check supply and return temperatures at the manifold, then rebuild, replace or reset the mixing valve.
One room never warms
A dead zone actuator on the manifold, a loop that was never balanced, or air trapped in a long run.
We test actuators and thermostats, purge each loop on its own, and set the flow for each room.
Boiler short-cycles in mild weather
A boiler sized for the coldest night of the year, firing into a small zone on a 55°F afternoon.
We set outdoor reset and minimum run times, and add buffering if the zones are very small.
Rust-colored water or sludge at the purge
Older radiant tubing without an oxygen barrier lets oxygen in, and that corrodes iron and steel parts in the boiler room.
We confirm the tubing type, then separate or protect the iron parts so the problem doesn't follow you to a new boiler.
Our step-by-step method for finding a slab leak without breaking up the floor is on the Eichler page; it works the same on any San Rafael slab. For repairs anywhere in Marin and Sonoma, see radiant heating repair.
Cold floors in San Rafael? We're a few minutes away.
Replacing the boiler behind a radiant floor
A radiant floor is the best match a condensing boiler can have. The floor only needs warm water, so the return water comes back cool enough for the boiler to condense and run at its rated efficiency. The gains come from setting it up for low temperature from day one.
Repair the system you have when…
- Each loop holds pressure on its own and the floors heat once the controls are right
- The problem is a mixing valve, actuator, circulator or thermostat
- The boiler is sound and parts are still available
- One leaking loop can be isolated, rerouted or repaired without touching the rest
Replace the boiler when…
- It's an old cast-iron or atmospheric boiler feeding radiant through a mixing valve and wasting heat all season
- The heat exchanger is leaking or badly corroded
- A Triangle Tube loses a major part: the maker closed in November 2025, so replacement parts and warranty help are gone. Our Triangle Tube guide
- It needs repairs every winter and is past 20 years old
What we design into a San Rafael radiant replacement
- Low-temperature design. Outdoor reset keyed to the floors, so the boiler runs the coolest water that keeps the house warm. San Rafael's mild winters mean that is most of the season.
- Separation from the floor piping. A low-loss header or primary/secondary piping, so the boiler gets the flow it needs and each zone gets its own.
- Manifold and zones. We reuse good manifolds, replace failed actuators and balancing valves, and add a purge station so every loop can be flushed and bled.
- Protection. A dirt and magnetic separator, a flush of the old system, and oxygen protection where the tubing needs it.
What a radiant boiler replacement costs in San Rafael
Ranges we publish for 2026. Your number depends on the house, and we put it in writing first.
What moves the price on a radiant system
- Number of zones. More zones mean more circulators or valves, more wiring and more balancing.
- Manifold work. Reusing a sound manifold vs. replacing actuators, flow meters or the whole manifold ($1,200–$4,500 for pump, manifold and valve upgrades).
- Mixing and controls. Whether the floors need a mixing valve or injection pump, or can run straight off a modulating boiler with outdoor reset.
- Venting and location. Garage, closet or crawlspace installs, and whether the vent can reuse an existing path.
San Rafael gets soft Marin Water (about 3.5–6.5 grains per gallon), so mineral scale in a heat exchanger is rarely what kills a boiler here. Corrosion from oxygen and iron is the bigger threat, which is why protection is part of every quote. All boiler replacement options.
A recent San Rafael radiant job
Lochinvar Knight for a 5-zone radiant floor system
This home's radiant floors are split into five zones. We installed a new Lochinvar Knight condensing boiler with a low-loss header separating the boiler from the floor piping, three ECM circulators, and a purge station so each zone can be flushed and bled on its own. The boiler now sends low-temperature water to the floors and only works as hard as the weather requires.
Older radiator homes in Gerstle Park and downtown
Radiators are less common in San Rafael than radiant floors, but the Victorians and Craftsman houses south of Mission Avenue still have plenty of them. In those homes the radiators are usually the best part of the system, and our advice starts there.
Steam or hot water?
Houses this old may have been built for steam and converted to hot water, or never converted.
We confirm the system type before quoting. A steam system can't simply take a condensing hot-water boiler.
Iron sludge
Old radiators and steel pipe shed magnetite, which clogs the small passages in a modern heat exchanger.
We always flush the system and fit a dirt and magnetic separator when we replace a boiler on an older iron system.
Too much boiler
Replacements sized from the old nameplate instead of the house cycle constantly.
We size from a heat-loss estimate. Big radiators often let a condensing boiler run cool most of the winter.
Permits and rules for a San Rafael boiler job
What applies inside city limits
Permits: a like-for-like boiler replacement in San Rafael is a simple over-the-counter permit with no plan review. New City applications go through the OpenGov portal (paper applications ended in February 2026). Santa Venetia and other unincorporated addresses are permitted by Marin County. We pull the permit and meet the inspector either way.
Historic homes: the City's Historic Preservation Ordinance requires Planning Commission review of exterior changes to landmarks and homes in a historic district, so on a listed house we plan the vent route before we quote.
Air rules: under the Bay Area Air District's Rule 9-6, home-size gas boilers manufactured after January 1, 2031 must be zero-NOx. Proposed amendments released October 2, 2026 would move that to 2033; the Air District Board votes November 4, 2026. New gas boilers can still be installed, and nobody has to remove a working one. San Rafael's all-electric rule for new construction was repealed and never covered replacing equipment in an existing home.
How a San Rafael radiant boiler replacement goes
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Map the system
Zones, manifolds, tubing type, mixing controls, and a pressure check on every loop before we price anything.
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Size to the floors
A heat-loss estimate and the floor area of each zone, not the old boiler's nameplate.
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Written options
Boiler with indirect tank vs. combi, which manifold parts to keep, and whether an air-to-water heat pump fits your floors and electrical panel.
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Over-the-counter permit
Filed with the City through OpenGov, or with the County for unincorporated addresses.
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Install and purge
Boiler, header, ECM circulators, separator and condensate neutralizer, then each loop purged one at a time.
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Tune and hand over
Combustion analysis at startup, outdoor reset set for the floors, and a walkthrough of every zone and thermostat.
San Rafael radiant floor & boiler FAQ
Who repairs radiant floor heating in San Rafael?
We do, from our warehouse on Andersen Drive. Radiant floors are the hydronic system we see most in San Rafael: boilers, mixing valves, manifolds, zone controls and leaks in the tubing. Call or text (415) 234-0370.
My boiler pressure keeps dropping. Is my slab leaking?
Maybe, but check the easy things first: the relief valve, the expansion tank and manifold fittings. If those are dry, we isolate and pressure-test each loop at the manifold to see whether one is leaking in the floor.
What does a radiant-floor boiler replacement run in San Rafael?
Most high-efficiency replacements run $8,500–$15,000; combis $11,000–$16,500; a boiler with an indirect water heater $19,000–$29,000 (2026 ranges). Zones, manifold work and venting move the number. Estimates are free and in writing.
Does a boiler swap in San Rafael need a permit?
Yes, but a like-for-like replacement is a simple over-the-counter permit with no plan review. Inside city limits it goes through OpenGov; unincorporated areas like Santa Venetia go through Marin County.
I have radiators, not radiant floors. Can you help?
Yes. We service and replace boilers on cast-iron radiator systems too, mostly in Gerstle Park and downtown, and we always fit a dirt and magnetic separator when replacing a boiler on an older iron system.
I'm in Terra Linda. Is this the right page?
Eichler radiant slabs have their own page: Eichler radiant heat repair in Terra Linda & Lucas Valley.
We work across San Rafael (Downtown, Gerstle Park, Dominican, Sun Valley, the West End, Bret Harte, Glenwood, Peacock Gap, Loch Lomond, Santa Venetia) and nearby San Anselmo, Larkspur and Greenbrae. More: Local Plumbing in San Rafael · boiler repair · radiant heating repair · boiler replacement.
Cold floors, a dropping gauge, or a boiler near the end?
Tell us about the house and the heat, and we'll send someone from Andersen Drive.
