Intro: French Drain With Dry Well
When I bought my house, I was told that "water collects in front of the garage door." What the owner didn't disclose is that every time it rains, the water that collects in front of the garage actually runs into the garage. This is obviously a problem.
Installing a drain out to the street wasn't an option. The driveway slopes away from the street, so a drain pipe that ran out to the curb would be well below street level when it got there. I considered a pop-up drain for that, but it was too risky. I also didn't have a good place to install a drain out to the street because of the layout of the driveway and house.
So a french drain was the way to go. I did a LOT of research online about this. A french drain by itself would have probably been fine. However, I was concerned that, since i don't have a large back yard, I would need more room for water to collect in the event of a heavy downpour. So, I resolved to dig a dry well at the end of the french drain for water to run into.
Step 1: Draw Your Plans
I sketched out what I was going to do with some rough dimensions. I suggest you do the same. You want to go into a project like this with a very clear picture in your head so that you're not making it up as you go.
I measured my lawn and decided on the proper depth for everything.
A traditional french drain is a drain that directs water away from an area via a trench filled with gravel. This allows the water to leech into the soil over a given distance, rather than pooling where you don't want it. Most french drains use holed corrugated piping or holed PVC. I used PVC for this project.
I opted to run my french drain into a dry well at the end. The well consists of a 55 gallon plastic drum ($35 on Craigslist) with holes drilled in it. It sits on a bed of 3-4" of gravel and is surrounded on its sides by about 6" of gravel. I purchased a toilet flange similar to this one, so the PVC pipe could securely connect to it.
The drain itself is an NDS 12-inch catch basin. I strongly recommend this over a drain grate unless your french drain is being fed by a downspout. By connecting your pipe to the catch basin, you're allowing water to flow into your drain without the silt or any other muck that might enter the grate.
Finally, I decided to add a drain/vent for the barrel at the end. It probably wasn't necessary, but I thought that an air vent could be good. It would also serve as a drain if water were to collect in the yard (though it never does). The 55 gallon drum already had a threaded 2" hole on the top of it, so finding the proper PVC connectors was easy.
Contact your city utilities hotline for digging BEFORE you break ground to ensure there are no gas, water, or power lines buried in your yard.
Step 2: Buy Materials
I really didn't spend much dough on this project. The catch basin was the most expensive thing. The pipe was super cheap. And the gravel and barrel I got on Craigslist. The 2nd load of gravel (pictured) I actually had to buy because the first load wasn't enough. Total, I needed about 2 cubic yards of 3/4"-1" gravel, which ran me about $65.
Step 3: Dig!
My friend Andy helped me. We ended up needing a pickaxe for the dry well. Soil was hard as rock after about 3 feet.
Step 4: Prepare the Barrel
Using a 1" drill bit, I turned this barrel into swiss cheese. Sides and bottom.
I measured for the toilet flange and cut with a drywall hole saw. A dremel would have saved me a lot of time and been a cleaner cut, but oh well.
Step 5: Line With Weed Barrier and Begin Filling in Gravel
Line your trench and dry well with weed barrier/landscape fabric. This will prevent dirt and silt from the ground from filling in around the gravel and preventing good absorption into the ground.
Then, create a 3-4" bed of gravel at the bottom of your pit for your barrel to sit on. Drop the barrel in, and move the gravel around until the barrel is level.
Connect the barrel and catch basin with your pipe.
REMEMBER TO KEEP THE HOLES IN THE PIPE FACING DOWN!
You can't tell from the picture, but I raised the catch basin up to the proper level (just below the pavement) by placing it on a bed of gravel. I filled in around the catch basin with gravel and road base sand to ensure that it would not move.
Step 6: Keep Adding Gravel!
Fill your trench with gravel until you have about 6 inches between the top of the gravel and the surface of your yard.
I had to buy a 2nd load of gravel (total of 2 cubic yards).
After you've filled in the gravel, install your drain vent on the barrel. Again, these are cheap pipe fittings from Home Depot. I used a 1x2 placed across the hole to ensure the level of the drain matched the surface of the lawn.
Drape the excess garden fabric over the top of the gravel bed so there is 1 layer covering it. It's okay if it overlaps a bit.
Step 7: Back Fill
Finally, begin backfilling your trench with dirt. I suggest packing it hard. The dirt will settle over time, but you want to help it as much as possible so there is no depression in the lawn.
I finished this project just in time for a week of rain here in LA, and it works great. My garage is dry as a bone!
Good luck with your french drain!