Eichler Plumbing: What Every Owner Needs to Know

Eichler homes are some of the most distinctive houses in the Bay Area. Open floor plans, post-and-beam construction, floor-to-ceiling glass, and slab-on-grade foundations. They were ahead of their time in the 1950s and 60s. The plumbing systems inside them, however, are now 60-70 years old and present challenges that most plumbers have never encountered.

We have worked on more Eichler homes than we can count across Marin County and San Francisco. Here is what every owner should know.

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The In-Slab Radiant System

The defining plumbing feature of most Eichlers is the radiant heating system. Copper tubing was embedded directly in the concrete slab during construction. Hot water circulates through these loops, warming the floor and heating the house.

When it works, it is one of the most comfortable heating systems available. Even heat, no forced air noise, no ductwork cluttering the attic. But these systems are now well past their expected lifespan.

Common issues:

• Slab leaks. The copper tubing corrodes from the outside in, eventually developing pinhole leaks. You notice when a section of floor stays warm when the heat is off, or when your water bill spikes without explanation.
• Loop failures. Individual loops can fail while others continue working. You end up with cold spots in specific rooms.
• Boiler incompatibility. The original boilers are long gone. Modern high-efficiency boilers operate at different temperatures and flow rates than the original equipment, and connecting them to a 60-year-old slab system requires careful engineering.

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Pressure Testing Before Any Work

Before doing any work on an Eichler radiant system, we pressure test every loop individually. This tells us which loops are holding pressure, which are leaking, and how much flow each one supports.

This is non-negotiable. Without pressure testing, you are guessing. We have seen contractors install a new boiler on a system with three failed loops and wonder why half the house will not heat. The boiler is pumping water into the slab and it is leaking into the ground.

Pressure testing takes time, but it gives you a complete picture of what you are working with before spending money on equipment.

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When to Abandon a Loop

Not every leaking loop needs to be repaired. In fact, most cannot be repaired because the copper is embedded in concrete. The practical options are:

Abandon and bypass. We isolate the failed loop at the manifold and remove it from the system. The remaining working loops continue to heat the rest of the house. Depending on the layout, you may not notice the difference, or you may need supplemental heating in that zone.

Re-route above slab. For critical zones, we can run new PEX tubing above the slab, either under the floor or along the perimeter. This is more work than abandoning, but it restores heat to the room without touching the slab.

Full system replacement. In severe cases where most loops have failed, it may make more sense to abandon the entire in-slab system and install a new radiant system above the slab or switch to a different heating method. This is a last resort and a major project.

We always discuss these options honestly. The goal is to keep as much of the original system working as possible, but not to throw money at loops that are going to fail next year.

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Connecting a Modern Boiler

The original Eichler boilers were simple cast-iron atmospheric units. Modern condensing boilers like the Navien NCB or Lochinvar WHN are dramatically more efficient but operate differently.

Key considerations:

• Water temperature. Old systems ran at higher temperatures. Modern condensing boilers achieve peak efficiency at lower return water temperatures. The system needs to be balanced so the boiler can actually condense.
• Flow rates. Old circulators pushed water at different rates than modern variable-speed pumps. Mismatched flow causes short-cycling and uneven heating.
• System flushing. Before connecting a new boiler to a 60-year-old system, the entire system needs to be flushed thoroughly. Decades of sediment, corrosion products, and old glycol will destroy a new heat exchanger in months if not removed.
• Water treatment. After flushing, the system water needs to be treated and monitored. pH levels, inhibitor concentrations, and dissolved oxygen all affect the longevity of both the old copper and the new boiler.

We wrote a detailed guide on why a new boiler can damage your Eichler if the installation does not account for these factors.

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Domestic Plumbing in Eichlers

Beyond the radiant system, Eichler homes have domestic plumbing that is now aging out:

Copper supply lines. Most Eichlers have copper supply throughout, which is generally in good condition. But the connections under the slab, especially where supply lines cross heating loops, can develop leaks from galvanic corrosion or ground movement.

Cast-iron waste lines. The original drain and waste lines are cast iron. After 60+ years, these develop internal corrosion, root intrusion at joints, and belly sections where the pipe has settled. Camera inspection is the right first step before committing to replacement.

Slab penetrations. Every pipe that enters or exits the slab is a potential leak point. The concrete-to-pipe interface cracks and shifts over decades. When we find a slab leak, we check adjacent penetrations because if one has failed, others are likely close behind.

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Finding a Plumber Who Knows Eichlers

Eichler plumbing requires a plumber who understands these homes specifically. The in-slab radiant system alone is enough to confuse a plumber who has never seen one. Add aging cast-iron waste lines, non-standard layouts, and the need to work around the distinctive architecture without damaging it, and you need someone with real experience.

Questions to ask:

• Have you worked on Eichler radiant systems before?
• Do you pressure test individual loops?
• Are you familiar with connecting modern boilers to in-slab copper?
• Can you show me examples of past Eichler work?

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Own an Eichler? Call us at (415) 623-6564 or schedule an assessment. We specialize in Eichler plumbing, in-slab radiant systems, and boiler replacement for Eichler homes. We service Eichler communities across San Francisco, Marin County, and the greater Bay Area. Visit our Eichler plumbing page for more on our approach.