The average home contains many drains, and you’re probably familiar with most of them since they’re part of a sink, bathtub, or shower. But there’s another type of drain you might not know about: perimeter drains.
What is a Perimeter Drain System?
Perimeter drain systems are an important part of your plumbing system. The perimeter drain itself is simply a perforated pipe with a mesh “sock” covering it (keeping soil out) that’s installed underground, circling the perimeter of your home. You might also hear perimeter drain systems called a weeping tile system.
Where is My Perimeter Drain System Located?
You’ll typically find your perimeter drain installed outside at the base of your home’s foundation.
Why Are Perimeter Drains Important?
Perimeter drains keep moisture out of areas in your home, like basements and crawl spaces. This is especially important as 98% of US basements experience some water damage, and with rain, melting snow, and rising groundwater, water can build up around your foundation and lead to cracks or other structural issues.
How Do Perimeter Drains Work?
The tiny holes in the perforated pipe allow water to (1) enter from the soil that has accumulated over time and (2) be carried and drained away from your home. The pipe will be out of sight—it’s covered in layers of gravel of varying sizes and then back-filled with soil to help water flow toward your main sewage system. In older homes, clay or concrete weeping tiles are used for the same purpose.
How Are Perimeter Drain Systems Installed?
Installing a perimeter drain system is a multi-step process.
- Plan the system installation. This requires figuring out where the water will go and checking for any buried cables or pipes.
- Dig a trench. Dig around the outside of your home, down to the bottom of the foundation.
- Clean the foundation. Brush off any soil and debris. Fix any cracks.
- Add waterproofing. Paint or attach a waterproof layer to stop water from soaking into the wall.
- Add gravel. Place a 3-4 inch layer of clean gravel bedding so the water can move easily.
- Install the drain pipe. Place a perforated PVC or corrugated pipe, holes facing down, on the gravel, and tilt it so water runs away from the house.
- Cover with more gravel. Add another 6-12 inches of clean gravel around and over the pipe.
- Wrap with a filter fabric. Use a mesh material to wrap the gravel and pipe to stop the soil and debris from clogging the pipe.
- Fill in the trench. Use soil to pack the trench so it stays firm and avoids settling.
- Lead water away. Make sure the water that drains away from the home’s foundation ends up in a safe area like a sump pump, storm sewer, daylight drainage point, or downhill spot.
How Can I Tell if There’s a Problem with My Perimeter Drain System?
The most common issue with perimeter drains involves the system becoming clogged with dirt, roots, and other underground debris. When this happens, water can seep into your basement walls. If you notice water in your walls, call a qualified plumber. Unfortunately, they’ll probably have to do some digging to reach the pipes.
Older homes that use clay or concrete weeping tiles to drain water are prone to more problems as they age, and will often become unusable over time. In these cases, the whole perimeter drain system or damaged parts of the perimeter drain system might need replacing. Sometimes, blocked tiles that haven’t yet collapsed can be fixed with a system flush. Again, this is a job for a qualified professional—they’ll be able to explain your options so that your home stays moisture-free.
What Is the Key Takeaway?
Perimeter drains protect your home by directing water away from foundations, basements, and crawl spaces. Proper installation with gravel, filter fabric, and waterproofing, along with regular inspections, keeps the perimeter drain system effective. Older systems may need flushing or replacement, but maintaining your perimeter drain helps prevent costly water damage and foundation problems.
