Complete a Gutter Downspout Extension Installation in 7 Easy Steps

Your home’s gutter system is incredibly important when it comes to keeping your foundation and yard in good shape. If your downspouts aren’t directing water far enough away from your home, knowing how to install a gutter downspout extension can help you correct the flow and get better drainage. Installing an extension in a trench is relatively easy and can be done in one or two days by following some simple steps. 

Safety Notes

Installing a downspout extension will require you to dig a fairly large trench. Before you do any digging, you must know where all of your plumbing and utilities are buried. Hitting a sewer main or natural gas line can be a costly mistake and can even result in serious injuries. If you aren’t sure where the lines are, contact your utility company and they will let you know where you can safely dig. 

You should also be very careful whenever you are cutting PVC pipe. Whether you are using a hacksaw or a powered circular saw, be sure to wear safety goggles at all times. PVC pipe can splinter and throw dust around when it is cut and you could end up with an injury if your eyes are not protected. 

Tools and Materials


  • Circular saw or hacksaw 
  • Level
  • Shovel 


How to Complete a Gutter Downspout Extension Installation Instructions

Step 1: Lay Out Your Extension 

Before you begin, you will need to lay out the path of your downspout extension pipeline. Make sure that the path is laid out at least four feet from the house to keep any leaks or runoff from seeping into your foundation. Using the stakes and string, lay out the path starting at the bottom of the downspout and ending at the drainage point. 

Place the stakes eight feet apart and include connections for any other downspouts along the way. Your home should have a downspout every 30 feet, so you will need to create extensions from these to your main pipeline. Once you are satisfied with the layout, sprinkle flour on the ground along the string. This will show you exactly where you need to dig your trench. Then, you can remove the string and stakes. 

Step 2: Dig the Trench 

Dig your trench along the path marked by the flour. The trench for your extension pipeline should be at least six inches wide and at a downward angle. The angle doesn’t need to be perfect, but it should be enough to allow the water to drain through the pipe. Place a long piece of wood in the trench as you dig and use the level to check the slope as you dig. 

Adjust the depth accordingly and remember that it should be at least 10 inches deep at its most shallow. This will prevent the pipe from freezing up during the winter since it will be below the frost line on the ground. The angle of your trench should drop the pipe at least 1.5 inches every 30 feet to ensure proper drainage. 

Step 3: Attach the Downspout Adapter 

Once you have dug your trench and gotten the angle where it needs to be, you can attach the downspout adapter. This will allow you to connect the circular PVC pipe to the rectangular downspout. You can glue this joint if you want to but many people choose to leave it unglued since the adapters are designed to fit onto the downspouts snugly. Cut a length of PVC and attach a 90-degree elbow to get the pipeline down into your trench. From there, you can begin laying down the rest of the pipe. 

Step 4: Install the Pipes 

Continue installing the pipes in the trench using elbows to make the necessary turns and cutting PVC to the proper length. As you work, check the angle of the pipes using your level before you glue the sections together. If you are noticing any areas that are either completely level or at a backward angle, take the pipes out and dig the trench slightly deeper on one end. Once the angle is set, you can then glue the sections of PVC together. 

Step 5: Attach Any Additional Downspouts 

If your pipeline comes along the path of any additional downspouts, you will need to connect those as well. Attach another adapter to that downspout and run a length of PVC to connect to the main pipeline using a T-fitting. The T-fitting will have one curved elbow. This elbow should be facing in the downstream direction as it will help move the water from the downspout into the flow of the pipeline. 

Step 6: Finish Installing the Pipes 

Once you have connected all the downspouts to the main pipeline, you can then finish your installation. Run the PVC to your drainage point, which should be far away from your home’s foundation and preferably in a rocky area or another trench filled with gravel. This will help the runoff seep into the ground safely without eroding the soil or creating a sinkhole.  

Step 7: Fill in the Trench

Fill in your trench with the dirt you originally dug out. It is helpful if you place the dirt onto cardboard as you dig out the trenches. This will allow you to simply lift one side of the cardboard and let the dirt fall back into place. Then, you can pack it in tightly with your shovel and ensure that the pipe and trench are completely covered. 

When to Contact a Professional

While installing a gutter downspout extension is not particularly difficult, it requires some amount of precision to ensure that the pipes are buried deep enough and are at the correct angle. A gutter professional will not only be able to make sure that your extension is properly installed, but they will also have the equipment needed to do it faster and more efficiently. If you also need any types of repairs on your gutter or downspout, a pro is the best choice. Contacting a professional is a good choice if you want the best possible final product that will protect your home and yard for many years to come.