How To Install A French Drain

Every homeowner should know how to install a French drain or find a plumber who can. When draining your yard or home, you will discover the importance of French drains.

Its name may indicate the drain is of French origin, but the truth is, it’s named after its inventor. 

The French drain is over 100 years old. It is popular among homes across the US. A better pipe or drain system is not available.  

What Is A French Drain?

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In the mid-1800s, Henry French, an agriculturist, invented the French drain. This is what the man is most famous for. His son, Daniel French, designed the Lincoln Memorial. 

Although the Lincoln Memorial may be more iconic, the French drain changed the way that we irrigate and drain water. The French drain is a concealed drain with many uses and variations. 

How Does A French Drain Work? 

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French drains help drain yards and gardens. The pipe is hidden underground and covered with rocks. It is pierced with holes so water from the surface can seep down and enter the pipe. 

The water follows the path through the pipe and works like any other pipe. The rocks must allow the water to flow underneath without becoming a hazard to the ground above. 

The purpose of the French drain is to move water that might build up and loosen foundations. It also helps remove overflowing water from septic tanks. 

How To Build A French Drain

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Building a French drain isn’t hard. But it’s best to follow expert advice and find a pro to lend a hand. 

Buying Materials

Before you start, make a checklist. Here is everything you need to install a French drain: 

  • Shovel
  • Pipe (PVC with holes or drain pipe)
  • Gravel
  • Fabric liner (water-permeable weed fabric)
  • Topsoil (optional)

Digging A Trench

You need to dig your trench 18 inches deep and 12 inches wide. This will hold the pipe while giving you room to work with. Feel free to go a few inches deeper, but try not to go deeper than two feet. 

As for width, 12 inches is the minimum. It’s important not to go narrower or else you’ll run into problems. Building a bigger trench won’t cost more, but a smaller one can in the end. 

Lining The Trench (Optional)

This is optional, but most recommend it. There’s no reason not to add a fabric liner to the trench before adding the pipe. A landscaping fabric will do and will prevent weeds from growing and disrupting the drain. 

Line the entire trench with it, pulling up over the edges. You can also wrap the drainpipe with fabric if you want, but one layer of fabric, or else the water won’t drain. Make sure the landscaping fabric is of good quality. 

Rock Bed For Pipe

After you line the trench, you can add a thin layer of rocks that will be the foundation for your pipe. With this, you can make up for any flat areas or holes. Make sure the pipe will be set in the bed. 

The pipe shouldn’t move much when you press down on it. But you also don’t want sharp rocks cutting into a pipe that is thin. Check for sharp rocks before pressing down and testing the pipe’s bed.

French Drain Installation

This is the most important step. Installing the drain. You can either use perforated PVC or a drainage pipe that will bend. Lay the pipe along the rock bed, making sure it is stable. 

It’s easier to work with a drainage pipe that is flexible more than a PVC pipe. PVC pipe may be solid, but it needs a solid base. Flexible pipe is also cheaper, but not as strong. 

Fill With Rocks

Fill the trench with rocks, covering both sides and the top of the pipe. Don’t leave room for movement or the pipe could shift and crack, or create kinks. Cover it well, all the way to the top unless you use the next step. 

Add Topsoil (Optional) 

If you cover the rocks and make the French drain “invisible” then leave an inch or two for topsoil. Add the topsoil to meet the rest of the ground and pack it tight. You can then add grass seed.

Keep in mind that if you need to do repairs or make changes, it’s better to have gravel to remove rather than grass and topsoil. This is why most French drains have a gravel cover instead of a topsoil cover. 

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Finding Someone To Install A French Drain/ DIY Project

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It may seem easy at first to find someone to install a French drain for you. Some general contractors can install French drains, but it’s most common for a plumber to install the French drain. Landscaping and waterproofing companies can also install French drains. 

Whoever you hire, make sure they are qualified and know the city codes. The cost of a French drain is $2,000 and $4,000. However, the range can be as large as between $800 and $8,000. 

To figure your quote, measure how many feet of drain you need. The average cost is $20 to $30 per linear foot or between $1,000 and $1,500 in exterior applications and $45 to $60 per linear foot or $5,000 to $6,000 for internal ones.

Frequently Asked Questions (FAQ)FAQ

Where Do I Drain To?

It’s important to have a safe release point. It should be an area below your yard and somewhere with little to no traffic. Digging a pond or something similar is a great way to utilize the release point without causing any further problems. 

Can I Drain Onto A Neighbor's Property?

You can never do this. Even if your neighbor’s property is bigger than yours and you have agreed to it. But it’s not a good idea to drain onto a neighbor’s property. To do so is illegal, and unless an agreement is written on paper it could backfire. 

How Do I Stay On Track - French Drain Mistakes?

To make sure that the trench follows the planned path, use flags, spray paint, or a chalk line to mark it before you start digging. This way, even if you have help, the team can stay on track without making any mistakes. 

Can I Drain Uphill?

No. For water to move uphill, it needs to be siphoned. This is a different type of irrigation system. Pipes should move downhill. In this case, at least one inch every ten feet.

Do I Need A Permit To Install A French Drain?

It depends on the code in your area. Contact an agricultural expert or official to find the city or neighborhood codes. You may be able to dig or you might need a permit that gives you the leeway you need. 

Do I Have To Use Gravel For My French Drain?

A gravel drain cover is recommended, but the soil is fine. If you do, you’ll need a corrugated pipe surrounded by polystyrene aggregate. The last thing to do is wrap it in the fabric and cover it with soil. 

Can I Hire A French Drain Installer?

Yes, you can. This will speed up the process and ensure it’s done right. You can also call them if problems arise.  

Are There Other Types Of French Drains? 

French drains come in many different varieties. Here’s a breakdown of what they are and their purpose.

Curtain drain – this is a concealed drain that is covered in soil with vegetation planted on top. They deal more with surface water instead of groundwater like the standard French drain does.

Filter drain – often used with a French drain, this type deals with groundwater alone.

Interceptor drain – used in city sewage systems or storm sewers. 

Dispersal drain – a multi-disperse drain that distributes water from septic systems.

Fin drain – a subterranean pipe with an upward placement. They direct water to a traditional drain. 

How Do You Clean A French Drain?

Keeping your French drain clean should be a priority. Cleaning a French drain is not hard but requires time and tools. 

First, remove the grate or drain lid. You will need access to the entire pipe. With a basic garden hose, flush any debris and other small items from the drain. For best results, a power washer removes large items from the drain.

If those ideas do not work, you’ll need to put an electric sewer snake in the drain. This is known as “snaking the drain.” It helps your remove debris or clogs from the drain.

You’ll need to force the snake through the drain. The goal is to remove any potential clogs from the drainpipe. During this step, it is vital that you take your time.

After you’ve hit the end of the drain, remove the sewer snake. When you do this, you’ll remove debris stuck in your French drain.

For the last step, use a garden hose to flush the drain system. Repeat this process to remove all clogs.

How Much Does It Cost To Clean A French Drain?

A pro plumber will charge between $45 to $150 an hour to clean a French drain. For big jobs, a pro will use a hydro jet to clean your French drain.

A hydro jet is a specialized tool that pushes high-pressure water through your home’s drain system. Due to its power and intensity, a hydro jet is not a DIY option.

If you have large dogs, then you know how much they shed. Pet hair can clog your drain system.

How Do You Install A French Drain In A Gravel Driveway?

As you know, gravel is used to make a real French drain. If you have a gravel driveway, you’ll need to use PVC pipe. The pipe should be four to six inches in diameter. This is big enough to drain water.  

The PVC pipe must be strong enough not to break when cars drive over it. If don’t have experience, call a pro. This isn’t a DIY home project for rookies.

Decide on the best place for your drain. It should be in a location where it can drain water without causing damage. Take 2-foot wooden stakes and place them at either end of the French drain.

If your driveway is longer than 50 feet, use a third stake to mark the extra length. Put a stake from 15 inches wherever the French drain is the highest. Use a dry line to measure the depth.

Dig a trench big enough so the pipe is flush with your driveway’s surface. Glue the PVC pipes together. When you lay the pipe, the holes need to be facing up.

Cover the pipe with gravel. Remember: the top part of the pipe should not be covered. You want to always see it.

How To Install A French Drain Conclusion

Now that you know the basics of installing a French drain, you understand how vital they are to your home. If you don’t know how to install one, do not teach yourself how to do it. Call a plumber, and they will teach you how to install the drain.

You don’t want to cut corners. Your house could flood if your drain is bad. Repairing a broken drain is not cheap. Plus, fixing flood damage is also pricey.