What Is a French Drain?

We thought we’d talk about a timely subject that’s been on a lot of people's minds this week after the heavy rains we’ve been experiencing these last couple of weeks – how can I avoid water intrusion from affecting my property. Two words – the French drain. Despite the name, the concept of the French drain isn’t from France — it’s named after Henry French, a 19th-century American farmer who popularized the theory. A French drain is a trench filled with gravel and a perforated pipe that redirects water away from a specific area. The pipe collects groundwater and surface water, then carries it safely away from your home — typically toward a lower part of the property, a drainage area, or a stormwater system. In simple terms, it’s an underground water diversion system.

French drains provide many benefits to your property. They are designed to prevent water from pooling near your foundation, which can weaken it over time, and reduce soil saturation around crawl spaces or basements, protect landscaping from erosion, and helps to eradicate soggy lawns and muddy walkways during the rainy season. They also help eliminate damp crawl space conditions that invite subterranean termite infestations, musty odors, and soil erosion. minimize hydrostatic pressure against foundation walls and help manage runoff during heavy rainstorms. Because many homes in Carmel and Monterey sit on sloped lots or coastal soils that don’t always drain evenly, water movement can become unpredictable. A French drain gives the water a controlled path to follow.

Once installed, French drains are hidden underground and don’t affect the curb appeal of your home at all, and proactive water management protects resale value. Drainage issues can be a red flag in real estate transactions. By addressing drainage issues early, you can prevent more expensive structural repairs later. Buyers often look closely at signs of water intrusion, so having a properly installed French drain can be viewed as a preventative asset.

How is a French Drain Different from a Sump Pump?

You may also hear about sump pumps when discussing drainage solutions. While both effectively manage water intrusion, they function very differently. A French drain is a passive system (no electricity required), which directs water away from the structure before it becomes a problem. It is installed underground around foundations or low spots and is a low-maintenance drainage solution once properly installed. A sump pump is an active system (requires electricity) that collects water in a pit and pumps it out and away from the home as needed. It is typically used in crawl spaces and basements, is not an option for homes that are built on concrete slabs, and requires maintenance and backup power planning.

Which Is Better?

It depends on the property. In many Monterey Peninsula homes — especially those without basements — French drains are often the more practical solution because they work with the natural slope and gravity of the property.  Sump pumps are more common in regions with deep basements and high-water tables. Most homes here have crawl spaces rather than full basements and experience frequent power outages during winter storms, which will affect the effectiveness of a sump pump. In coastal California, French drains are generally more prevalent for exterior drainage control.

Final Thoughts

French drains may not be visible, but they play a significant role in protecting homes, especially in coastal communities where winter rainfall and varied terrain are part of life. If you're buying or selling property in the area, understanding how drainage systems work can help you better evaluate a home’s long-term condition. A well-designed French drain system isn’t just a landscaping feature — it’s an investment in structural protection and peace of mind.