Ideally you will install your patio drain before the cement is poured in the initial patio construction. If, however, this is not possible, you can add the drain into an existing patio slab. It is important when planning your patio drainage system to make sure that the water is not flowing towards the house. Water can seep into the foundation and weaken it.
Step 1: Where Does It Go
You need to determine the best location for your drain or drains. The best way to do this is to spray the patio surface with your garden hose. The water will start to collect at a certain point on your patio. If you're lucky, it might just run off the patio all together, sparing you the need to cut the concrete. Mark the needed drain locations.
Step 2: Cut and Dig
You will need to break through the concrete in order to place a drain underneath it. Either drill or have someone drill a hole in the concrete just wider than the pipe you will be using for the drain. Dig underneath the patio until you reach this hole. You can use a high-pressure hose and pipe to try and wash out a direct channel to the hole without washing away too much excess dirt.
Step 3: Connect The Joints
Push the PVC drain under the patio and add an elbow joint when it reaches the drain hole. Then add however much pipe it takes to reach just below the surface of the concrete. Fill the side of the pipe with dry cement and then wet it. This will fill in the gap and keep the pipe sturdy. Cover your drain with the drain cover.
Step 4: Don’t Crack It
Fill in the area below the patio that was washed out. Use a long handle to press gravel into the crevices. This will help to keep the concrete from bowing under weight and missing soil underneath it.
Step 5: Where Does It Go
Just getting the water off your patio does not solve your drainage issue. You must direct the water to get it to flow away from the patio and house as well as any other undesired areas. Ideally, you can join this drain system with an existing system in the yard. If you do not have one you will need to dig a trench to guide your new PVC drainage to flow to the street or garden area.
Step 6: Continue the Journey
If you do need to continue your drainage to flow from the patio, you will want to dig your trench a few inches deeper then the height of the PVC. Place pea gravel underneath the pipe then again on top of it. You will then place soil on top of the pea gravel and then either replace the grass or make new shallow plantings on top of it. You should allow for at least 4 inches of soil on top of the gravel.
By creating a well-draining and puddle free patio it will help to make your patio last longer. With the water unable to settle in one spot for an undetermined amount of time no rot or mildew can form. You can continue to use this knowledge to create a puddle free yard as well.