Last Updated: October 16, 2022

Retaining Wall Drainage Guide

Written By: Pool Care Guide

Retaining walls are popular pool features. They are cosmetically attractive and are particularly advantageous if your pool is near the start of a slope and needs extra structural support to keep it sturdy. However, many lack an effective drainage system.

If you are building a retaining wall, you need to ensure it has a proper draining system so it does its job well over the long term. In this article, you will learn why retaining walls need proper drainage and the steps you can take to ensure it does. 

Why Your Pool Retaining Wall Needs Drainage

Today, pool designers put a lot of focus into the structural design of a pool’s drainage. Every inground pool needs drainage that directs runoff away from the surrounding area. 

When designers add a retaining wall with drainage, it helps maintain the natural flow of runoff water and reduces the chances of sitting water under or around your pool. Any excess water under or sitting against the pool’s structure can lead to serious problems, often causing caving, crumbling, or leaning retaining walls. 

Moreover, allowing your retaining wall to drain water keeps its structure and position still, especially when built against a slope. Water is powerful, causing the flow of extra soil and rocks against or into your pool. 

Without proper drainage installation within the retaining wall, water will begin its inevitable force of flowing through the wall. Over time, water and soil might leak through the wall, changing its overall appearance. Specialized drainage solutions will keep your retaining wall’s structure looking forever new.

How To Build a Pool Retaining Wall With Proper Drainage

If you’re planning to install a pool in your yard, you’ll want to consider a retaining wall with proper drainage from the get-go. Committing to one from the beginning of your project will allow for extra building room and less clean-up around the pool. 

The building process of a retaining wall with proper drainage will vary depending on the environment and building supplies available to you. However, the majority of such building projects will follow a similar step-by-step process:

Plan and Obtain Permits

As with any building job, you need to follow a well-defined building plan. With that in mind, create a rough draft drawing of the area you plan to excavate. Visualizing the details of the wall will ensure you don’t veer off your build goals and end up with something that doesn’t meet your needs. 

Your next step will be to consider what permits are required to ensure everything related to your project is above board. Moreover, having the necessary permits will allow you to build retaining walls of greater heights if required. You aren’t likely to need a higher retaining wall unless your pool is near the bottom of a slope greater than five feet.

Excavate and Add the Gravel

Now that you have dealt with the prerequisites, it is time to begin the hands-on process. 

One of the most crucial parts of building a retaining wall with drainage is to factor in the dimensions of the wall. If you want to guarantee that your structure can support itself, it’s best to make the wall's depth about 18 to 24 inches in the ground and 24 inches in width. The last thing you want is a narrow retaining wall that could buckle over. 

As you dig a trench to where the wall will sit, consider the wall’s height against the slope to ensure that the wall will sit higher than the slope’s lower end. 

Then, you can add crushed gravel in the bottom of the trench, compacting it to give the foundation something to stick against. In addition, apply gravel behind the wall between a height of six and 12 inches. 

Construct the Wall and Add Drainage

Most retaining walls consist of stone, brick, or similar building blocks. Other materials, such as concrete or rebar, can be used but may not be as effective. If you choose the latter two options, be sure to leave space for the drainage pipes. 

Next, you will want to lay a perforated PVC pipe along the bottom of the wall to collect the water runoff. You can opt to insert drainage pipes at the wall's bottom within the first layer of building material or at each end of the wall. Always wrap your PVC pipe in cloth to prevent soil and rocks from entering the pipe, slowing down the water flow. 

After the drainage pipe sets behind the wall, add gravel on top of it to protect it. Now, you can finish building the wall to your desired height before backfilling the wall.

Add Soil and Gravel as a Backfill

The last part of the building process is almost complete. Once you finish installing the retaining wall and its drainage system, you can begin backfilling the wall with soil and gravel. 

To avoid any unwanted soil or gravel penetrating through cracks, place mesh along the backside of the wall. After the bottom layer of gravel becomes compact without breaking the drainage pipes, you can fill the back side with extra gravel or topsoil until a height of about six inches from the top. 

Leaving some room at the top of the wall will prevent water from overflowing.

Other Things To Consider

If you are building a pool on a flat surface away from slopes, you shouldn’t have to deal with the issues associated with drainage. Still, the risk can’t be entirely eliminated, so it’s essential to be mindful of natural water runoff in areas where water can build up. 

To give yourself an extra layer of protection, you might want to think about diverting some of the water before it gets to the retaining wall. Doing so will alleviate much of the pressure reaching the final drainage point in the wall. 

Final Thoughts

A retaining wall with a proper drainage system offers excellent protection for pools at risk of water build-up. Just remember that any retaining wall project needs to be thoroughly planned out. So, get the necessary permits, make drafts, and follow the build process meticulously to ensure the best results for long-term water flow. 

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