How Do I Choose the Best Drainage Gravel?

Angela Crout-Mitchell
Angela Crout-Mitchell
Drainage gravel may be used for landscaping purposes.
Drainage gravel may be used for landscaping purposes.

Drainage gravel is commonly used in variety of different applications, including landscaping and construction. Almost all types of gravel can be accurately described as loose rock. Some types of landscaping gravel is comprised of smooth round stones, while others are a combination of crushed stone. Gravel can serve a variety of specific purposes, dependent on the size, material type, and the geographic location of the stones. Not only do many types of gravel assist in water drainage, but gravel also enhances landscape design.

Crushed rock is typically 1 to 2 inches in length.
Crushed rock is typically 1 to 2 inches in length.

The crushed stone varieties of drainage gravel consist of shell gravel and crushed rock. The crushed rock is usually 1 to 2 inches (approximately 2.5 to 5 cm) in length, and is used for a number of purposes including driveway installation, building foundations, and large drainage areas often found near industrial buildings. Gray crushed stone gravel is the most common type of gravel. As its name implies, shell gravel is made up of ground shells and other natural materials found on beaches and in coastal areas. This type of natural gravel can be used in the same manner as crushed rock and is most commonly used in the regions where it is produced.

One way many homes aim to avoid flooding is to have a rainwater runoff system that empties into the sewer system.
One way many homes aim to avoid flooding is to have a rainwater runoff system that empties into the sewer system.

Most other types of landscaping drainage gravel include stones that are either naturally rounded and smooth or manufactured to appear round and smooth. River rock is a popular type of smooth gravel and is usually 1 to 2 inches (approximately 2.5 to 5 cm) in diameter, though it can be found in larger sizes. This rock type is often installed in ponds or areas with minimal foot traffic. Pebbles are another type of rounded landscaping drainage material and are usually much smaller in size than river rock. French drain applications typically employ pebbles to enhance the appearance of drainage systems close to buildings and homes.

Poorly designed drainage areas can become a breeding ground for mosquitoes.
Poorly designed drainage areas can become a breeding ground for mosquitoes.

Most types of drainage gravel are available in many different colors and sizes, with the exception of gray crushed rock. Decomposed granite is normally gray as well, but has streaks of silver and white for visual interest and is available in many different sizes. Pea stone or pebbles are sold in off white colors accented with yellow, tan, or brown, with varying shades of tan and caramel for variation. Crimson stone, with its unique shades of red and diverse stone sizes, is a popular choice as well. Local nurseries and garden centers offer enormous selections of drainage gravel for remodeling and construction needs.

How To Build a Gravel Pit for Drainage?

While some people prefer French drainage systems, gravel pits or modified dry wells work better for specific purposes. Depending on the yard's grade and how much the budget for the project is, and of course, the level of handiness and ingenuity, gravel pits may be a more straightforward fix for pooling water. However, no easy fix ever comes without complex considerations.

When building a gravel pit for drainage, homeowners must consider reselling value for their property before spending the time, effort, and costs to inset a gravel pit. The pit is what it claims to be, a hole in the ground filled with gravel wherein excess water is meant to drain rather than create a soggy mess in the backyard.

Though, trading one wet spot for another is rarely the best approach to fixing a problem. Gravel pits might be best considered a band-aid approach if homeowners need time to save more money for property grading or lawncare renovations.

Two Drains, One Pit 

There are two different approaches to gravel pits. One option for gravel pits is simply to dig out the place in the yard that lacks graded flow and install a trench to fill with gravel or a trough and then gravel.

Another option for a gravel pit is a variation of a French drain. Some homeowners are unwilling to uproot a portion of their backyard and fill it with gravel, depending on the location, and rightly so. Gravel pits can be an eyesore and a hazard if not adequately planned into the landscaping. To prevent an unbecoming gravel pit mid-yard, a slim carrier trench must be dug to take to water flow further on the property where a gravel pit can safely be installed, out of sight and out of danger of trips and falls.

Materials

Regardless of how you plan to construct your gravel pit, you will require the same basics to start the job.

  • PVC piping drain
  • Tank or trough 
  • Adapter for downspout 
  • Landscaping sheet 
  • Gravel 
  • Power drill 
  • Shovel 

Directions 

  1. Begin by digging a slim trench from your downspout to an area further out in your yard. The channel should be about 6 inches wide and increase in-depth as it gets closer to the gravel pit for proper drainage. 
  2. When you reach the area on the yard where you will build the pit, measure the size of the tank or trough that you have for drainage and dig a hole that size plus 6 inches on all sides to prevent erosion. The hole depth will depend on how long your trench is and how far it is graded toward the trough. Depending on the size of the trough, you might use a backhoe for this step. 
  3. Attach the adapter to the downspout and run the PVC pipe from the adapter to the pit. 
  4. Be sure that the pipe sits atop the tank or trough for proper drainage.
  5. Drill holes in the trough or bucket for slow drainage and prevent erosion.
  6. Fill trench and hole with tank or trough with gravel to top. 
  7. Add a layer of landscaping sheet to the top of the gravel and then add another layer of gravel on top to help retain rock rather than lose it. 
  8. Keep extra gravel on hand. As the layers settle, adding additional gravel over time will likely be necessary to cover the landscaping sheet completely. 

Additional Options

Clearly marking the gravel pit and the trench that leads to it helps prevent trips and falls. Children, lawn maintenance crews, and even homeowners can have a misstep that leads to a rolled ankle or worse when the graveled areas are not identifiable. Adding landscaping features to the sides of the installation or using solar lights to alert anyone passing by will help improve safety.

What Size Gravel Is Best for Drainage?

The ideal gravel size for drainage will depend primarily on your purpose and how the gravel is installed. Pea gravel is the most desired size for gravel pits and French drains. The dimensions of pea gravel are roughly ½” to ¾,” and the pieces have been washed to remove any fine particles that could prevent proper drainage.

How Does Gravel Help With Drainage? 

Gravel helps promote drainage because it accomplishes two primary goals that other materials do not. First, gravel is fine and packed close enough to stop more oversized items like leaves and other debris from entering the drain and blocking drainage. Second, gravel is large enough to allow water to slowly drain into the surrounding ground without overflowing and compacting, leading to pooling.

What Types of Drainage Gravel Are Normally Used?

When deciding upon drainage for a home or business, it may be decided that gravel is going to be a part of the system. Among the many types of gravel available, some types are best suited for drainage due to the characteristics of the specific stones.

Size Matters

Larger-sized gravel will be more ideal for drainage. Stones with a size of half an inch to one inch across are the right size for blocking debris, yet allow for water flow. Larger rocks won't accidentally become compacted during heavy flows.

Choosing Layers

The lower layer of gravel in the drainage system will not be seen. It is wise to pick gravel here that gets the job done, but doesn't need to be pretty. Clear drainage stone works great in this application because of its size and smoothness. It is fairly cheap and available almost everywhere. For the upper layer that will be seen by people, the aesthetic of the stones comes into play.

Here are some of the more popular choices:

  1. Pea Gravel - Top Layer
  2. River Rock - Middle or Bottom Layer
  3. Pink Quartz - Top Layer
  4. Crushed Stone - Middle or Top Layer
  5. Marble Chips - Top Layer
  6. Base Gravel - Bottom Layer

Depending on where a project exists will also determine what gravel is available to purchase. Many local gravel yards purchase stones locally and sell them to customers locally. Projects near a beach are more likely to get crushed seashells in the available gravel than projects farther inland.

Best Drainage Gravel for Landscaping

Where is the Project Located?

Location always has some influence on what materials a project will use. Projects tend to mimic the aesthetic of the surrounding town and culture. Materials available for a landscaping project in Nevada will be much different than the materials available for landscaping in Florida. Speaking with some of the local gravel providers will help get an idea of what is available to buy. Shipping in some exotic gravel from a far-off area can be done, but will certainly cost a lot more.

What Sort of Drain Is Being Built?

There are quite a number of creative ways to build drains into landscaping with gravel. Some drainage systems can be multi-layered and get pretty complicated. Some systems will be visible up to the surface with gravel, while others will hide the gravel underneath the grass. The best gravel choices might change depending on the usage within a project.

People will often speak about a French drain. This is basically a ditch lined with gravel. This sort of ditch can be assisted with perforated pipes to send the water off to a larger system, or it can just slowly drain the water into the soil.

Which Layer of a Drain System?

Typical layering of a drainage system uses larger rocks on the bottom layer and progressively smaller gravel towards the top layers. This ensures good flow and less chance of the rocks compacting together and preventing water passage.

The bottom layer of gravel will not be seen, so choosing a stone for its utility here is more important than looks. The middle and top layers should be chosen for its purpose and looks. If the top layer isn't going to be covered by sod, it will be visible. Depending on the neighborhood and the available rock in the area, the top layer of gravel might be chosen for its colors or for its cultural history.

Crushed Stone vs. Pea Gravel

Both crushed stone and pea gravel are not very good drainage rocks. Pea gravel, sometimes called pea stone, is a little too small for good drainage; running a little smaller than half an inch across. This type of stone is adored for its mix of colors and smoothness. This would actually work well as a top layer in a system, but will compact too much in the middle and bottom layers.

Crushed stone, on the other hand, has hard edges and is usually cut a bit larger than pea gravel. Similar to pea gravel, however, crushed stone usually isn't very good for drainage because of how small it is. Crushed stone isn't admired for its beauty, but it has the right size and shape for the middle drainage layer.

A rock more suitable for the bottom layer of a drainage system is base gravel with an average width of two inches. This gravel has fairly large individual rocks that won't compact and form pools in the drainage system. Large, coarse gravel permits the flow of water. Always use larger gravel in the bottom layer, with smaller gravel being suitable for use in the middle and top layers.

Discussion Comments

anon963909

This article does not really answer the question of how to choose drainage gravel.

Shevardnadze

My old house had a drainage problem that caused a wet basement. My parents solved this by putting down an insulating material around the house and covering it with large gravel. This was a drainage solution for the basement and it was pretty to have the house surrounded by white gravel and then green grass.

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    • Drainage gravel may be used for landscaping purposes.
      By: marilyn barbone
      Drainage gravel may be used for landscaping purposes.
    • Crushed rock is typically 1 to 2 inches in length.
      By: Virynja
      Crushed rock is typically 1 to 2 inches in length.
    • One way many homes aim to avoid flooding is to have a rainwater runoff system that empties into the sewer system.
      By: Aaron Kohr
      One way many homes aim to avoid flooding is to have a rainwater runoff system that empties into the sewer system.
    • Poorly designed drainage areas can become a breeding ground for mosquitoes.
      By: demarfa
      Poorly designed drainage areas can become a breeding ground for mosquitoes.