Triangle Tube Boiler Replacement in Kentfield: An NTI TRX Upgrade

If your home has a Triangle Tube boiler, you've probably read that the company shut down and parts are drying up. Here's what replacing one actually looks like, from a job we finished in Kentfield earlier this month. If you have a Triangle Tube and want a straight answer on repair vs. replace, call or text Local Plumbing at (415) 234-0370.

The Home and the Problem

This Kentfield home is heated by a hydronic system, and its heat and domestic hot water both came from a Triangle Tube combi boiler. Combis like this were popular in Marin over the last 15 years: one wall-hung box, radiant heat plus on-demand hot water, and a compact mechanical room.

The trouble is support. Triangle Tube ceased operations in November 2025. There's no factory warranty or tech support anymore, and replacement parts are only available while distributor inventory lasts. (Our Triangle Tube shutdown post covers the details and the recall.) For a heating system you depend on all winter, that's a risk, especially in October with the rainy season starting.

It wasn't the only one we saw. Two weeks earlier we replaced a leaking Triangle Tube Prestige in Terra Linda with an NTI TRX150. Across Marin, these boilers are reaching the age where a failed part may not be replaceable.

What We Found

When we evaluate a Triangle Tube, we look at more than whether it fires today:

• Age and service history. Has the heat exchanger been cleaned on schedule? Are there signs of past leaks?
• Parts risk. Which components are likely to fail next, and can we still get them?
• How the house uses hot water. A combi heats domestic water on demand. In a larger home with several bathrooms, that can mean the hot water side struggles when two showers run at once.
• Piping and venting. Can the new boiler reuse the existing vent path and near-boiler piping, or does it need a cleaner layout?

For this home, the answer was clear: replace the boiler now, on the homeowner's schedule, rather than wait for a failure in January.

What We Installed and Why

Boiler: NTI TRX199 (TRX199S2)

We chose an NTI TRX199, a condensing, modulating boiler (19.7–199 MBH, 95% AFUE) with a stainless steel heat exchanger. NTI is one of the brands we install most in Marin. It's well supported, parts are easy to get, and the TRX series modulates down low enough to run radiant floors gently and efficiently instead of cycling on and off.

Hot water: NTI S20W indirect tank

Instead of another combi, we paired the boiler with an NTI S20W indirect water heater, a 20-gallon stainless steel tank heated by the boiler. An indirect tank gives the house stored hot water plus boiler-speed recovery, which handles simultaneous showers better than an on-demand combi. It also takes the water heater question off the table: no separate gas water heater, and no gas water heater replacement to plan around the 2027 Bay Area rule.

The rest of the system

• Grundfos Alpha circulator with Webstone isolation valves, so pumps can be serviced without draining the system
• ProPress copper fittings and Type M copper near-boiler piping
• New PVC venting and a condensate neutralizer, so the acidic condensate is treated before it goes down the drain
• A full system flush and Fernox F1 treatment to protect the new heat exchanger from corrosion and scale
• Pressure testing, air purging, combustion analysis, and setup of both the heating and hot water loops

Existing zone wiring and components outside the replacement scope were inspected and reused where they were in good shape. We don't replace parts that don't need it.

The Result

The home now has a supported, high-efficiency boiler with factory parts and warranty behind it, quieter and steadier radiant heat, and an indirect tank sized for how the family uses hot water. The work is backed by Local Plumbing's labor warranty on top of NTI's manufacturer warranties.

Kentfield Homes and Boilers: What We See

Kentfield, Greenbrae, Kent Woodlands, and nearby Ross have some of the most hydronic-heavy housing in Marin: larger custom homes, radiant slabs under hardwood and stone, and mechanical rooms tucked into lower levels. A few local patterns:

• Combis that were sized for the heat load but not for hot water demand. Fine when they were new, frustrating as families and bathrooms grow.
• Multiple zones and mixing valves that need to be set up correctly with the new boiler, not just reconnected.
• Damp lower-level mechanical rooms in the Ross Valley, where corrosion on fittings and vent connections shows up earlier.

Boiler work is year-round, but replacing before the heating season is much easier on everyone than an emergency swap on a cold night.

Triangle Tube Replacement FAQs

Do I have to replace my Triangle Tube boiler right away?

No. If it's running safely and has been maintained, you can keep using it. Have it serviced, check whether it's affected by the recall, and have a replacement plan ready so a failed part doesn't leave you without heat.

What should I replace a Triangle Tube combi with?

It depends on the house. For many Marin homes we recommend a modulating condensing boiler, like the NTI TRX, paired with an indirect tank, which handles heavy hot water use better. Smaller homes may do well with a new combi.

Can gas boilers still be installed in the Bay Area?

Yes. Under the current Bay Area Air District rule, home-size gas boilers made after January 1, 2031 must be zero-NOx (a July 2026 draft would move that to 2033). New gas boilers can still be installed until then.

How long does a boiler replacement take?

Most direct replacements like this one take a couple of days, including flushing, setup, and testing.

Boiler Replacement in Kentfield, Greenbrae, Ross and San Anselmo

Local Plumbing specializes in boiler and radiant heat systems across Marin and Sonoma counties. We do combustion analysis on every boiler service, and our warehouse and training facility is in San Rafael, minutes from Kentfield. We're a licensed C-16 and C-36 contractor (Lic #1091739) with 340+ five-star Google reviews. See our boiler replacement page or our NTI boiler page.

Have a Triangle Tube, or another boiler that's getting hard to service? Call or text (415) 234-0370, or contact us, for a free replacement estimate.