A french drain is a popular way homeowners divert water in problem areas out of their yard. If your yard has drainage problems you might notice pools of standing water start to form. A french drain will help eliminate that.
Ten Steps To Install A French Drain:
- Check Zoning Laws
- Decide Where The Drain Will Go
- Dig A Trench
- Line Trench With Fabric
- Install Gravel Bedding
- Add Pipe Connectors
- Install Pipe In Trench
- Cover Pipe With Gravel
- Cover With Landscaping Fabric And Soil
You will need to have certain tools and materials to do the job, but even a beginner can install a french drain in a day or two. If the french drain is under 20 or 30 feet you could probably do the job with a shovel being your only tool needed. But if you have problems digging trenches with shovels or just don’t want to, you can rent a trencher to get the trench dug in no time.
Materials Needed For A French Drain
- Drain Grates
- Landscaping Fabric
- Drainage Pipe
- Couplings And Adapters
- Gravel Or Landscape Stone
The drain grates are to go on either end of your french drain. They allow the water to enter and exit the drain properly. Make sure you get a size that will fit the size drainage pipe you are getting. I recommend a 4 inch perforated drain pipe that is corrugated and flexible. The perforations allow water to enter the entire length of the french drain.
Here’s a video explaining how a french drain works, if you already understand this, just skip below to the steps.
You may not need a flexible drainage pipe if your french drain is going to be a straight shot. But typically there will be some ups, downs, and turns and a flexible pipe will make the job a lot easier. Make sure you get the couplings and adapters you will need to connect the drainage pipe from start to finish.
Lastly, you want to have a good amount of landscaping stone or gravel. Anything that will allow water to pass easily through it and into the french drain. I find gravel works the best and is usually relatively cheap. When you have everything you need it’s time to get started.
Step 1. Check Zoning Laws Before Digging
You will want to make sure you are not breaking any zoning laws or building codes before you start digging in your yard. Not only because you are digging, but also because some areas have regulations around drainage. If you live in an HOA, they might have rules about altering your yards drainage as well.
Most of the laws that would prevent you from installing a french drain have to deal with water runoff entering the local storm water systems. You may need to submit for an approval of some kind. If you do not get approved, I would consider a dry well or another form of drainage that won’t impact local laws.
Step 2. Decide Where The Drain Will Go
You should already have a good idea where the water is pooling, but also consider where the french drain will divert that water. You want the french drain to start in the problem area and drain away from your house if at all possible.
Plan for the outlet of the drain to be downhill towards nearby water sources if you have any. Definitely try to avoid draining into a neighbors yard. You could possibly divert the water near a drain on the street or curbside if have to. Make sure that wherever you put your outlet, it isn’t going to just cause another pooling problem later on.
Use stakes or marking paint to mark where you want your drain to go. This will help in the next step when you start digging. If you plan on renting a trencher I would go with a brightly colored marking paint.
Step 3. Dig A Trench
This step is the hardest part of the whole job if you’re digging with a shovel. If you have a long stretch of area to cover you might be better off renting a trencher. Renting equipment can sometimes get pricey, but you should only need it for the day, maybe half a day. If you can pick it up yourself that might save you some money too.
Dig the trench from the problem area, where you need your french drain to start, to the outlet area you chose. Dig the trench a foot and half deep (18 inches) and about 10 to 12 inches wide. In a best case scenario your trench will have a minimum 1% grade and run horizontally across a slope. A 1% grade is about an inch drop for every 10 feet give or take.
Step 4. Line Bottom Of Trench With Fabric
After the trench has been dug you want to line the bottom of it with weed barrier or some type of water permeable landscaping fabric. Make sure you use enough fabric to reach the bottom of the trench, up the sides, and at least 10 inches outside of the trench on both sides.
This fabric is an important step that will keep your french drain clear of dirt, roots, silt, and anything else you don’t want in there. For big jobs consider buying the fabric by the roll. Here’s an example of a Durable Landscaping Fabric to give you an idea of what to look for.
Step 5. Install Gravel Bedding In The Trench
Pour about 3 inches of gravel or some type of landscaping stone down the length of the trench on top of the fabric. You will want to compact the gravel a little bit to avoid shifting after the job is done. This gravel will act as a nice solid bedding to lay the drainage pipe on top of.
Step 6. Add Couplings And Connectors To Drainage Pipe
Connect an inlet grate to one end of your drainage pipe and lay it near the start of the trench. The inlet grate will allow water from the problem area to enter the french drain. Connect sections of drainage pipe together with couplings until you have one long connected piece of pipe that will run the length of the drain.
You should have one long drainage system now sitting next to your trench. Some people like to connect the pipe in the trench as they go. I found that you could end up getting pieces of gravel in the drain if you do it that way.
Step 7. Install Pipe In Trench
Now simply lay the connected drainage system into the trench. If you did go with the perforated pipe, make sure the perforation are facing down. Make sure the pipe is sitting nicely on top of the gravel bedding.
You can test the flow of your drainage system now by pouring some water down the inlet. I usually let a hose run into it for a little bit to make sure everything is working fine before continuing to the next steps
Step 8. Cover Pipe With Gravel
With the pipe in place and working as it should, start to fill in the trench with gravel. The gravel should be poured in between the fabric and the pipe. Cover the pipe with a few inches of gravel and pack it down nicely. Avoid compacting too hard at this point, you don’t want to crack the pipe.
Make sure the gravel is not piled above ground level. You may want to apply soil and plant grass over the gravel later on. Leave yourself a few inches just in case.
Step 9. Cover With Landscaping Fabric And Soil
Now wrap the excess fabric over the top of the gravel. This will add another layer of protection. At this stage your drainage pipe should be encased in gravel, and wrapped in landscaping fabric or weed barrier.
Now you can cover the trench with soil. This step is really optional. You should cover the drainage system with something, but some people prefer to cover it with gravel instead of soil and grass. If you ever need to get back in there later on to fix a blockage or something, the gravel is a lot easier to dig up and replace.
Pro Tip: Cover the inlet with duct tape or cardboard while you fill that area in with soil. This will prevent dirt from getting into the drainage system.
If you feel uncomfortable or unable to do any of these steps, you could always look into HomeAdvisor Landscaping for top rated local professionals that could help you out. Most landscaping companies can install a french drain, and I’ve found some good companies on there before.
Step 10. Maintain
Aside from reseeding the dug up area, there shouldn’t very much maintenance you need to do here on out. Occasionally check the outlet for blockages and remove any dirt or leaves piling up on the inlet.
Gravel And Fabric Free French Drain
I do want to mention this option. They make a corrugated slotted drain pipe surrounded by polystyrene and wrapped in fabric all ready to be put in the ground. This option would eliminate the gravel and landscaping fabric steps.
I don’t like this option because dealing with this type of pipe can be a pain when it comes to connectors and couplings. And it ends up being a lot more expensive per foot to buy this specialty drain pipe. You still have to dig the trench either way, which is the hardest part anyway. For me personally, putting some fabric and gravel in a trench is not a big deal.
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