Dry Well Vs. French Drain: What Are They And How They Are Different?

Poor drainage, especially during a heavy downpour can lead to swampy yards, which can cause serious damage to your property over time since the water has nowhere to go. 

While there are quite a lot of ways to solve the drainage problems that might not only threaten your property, but also that of your neighbors’,

In today’s episode of how to deal with a waterlogged lawn, we will discuss dry well vs. French drain!

What Is A Dry Well?

dry well

Simply put, dry wells or soak wells or soak pits or soak ways, as called in different parts of the world are nothing but underground pits that are designed to collect runoff water from gutters and drainage pipes.

They are usually installed in the lowest points of your lawn so that the water can easily run into the hole in the concept of gravity.

While the idea of all kinds of dry wells is the same, the structures can be different.

For instance, the simplest version of a dry well is a hole in the ground that is packed to the brim with gravel or other rocks, where the water seeps in and is slowly diffused into the soil.

However, when the flooding is more severe, it calls for more advanced version of a dry well.

That typically involves setting up a porous barrel made of concrete or plastic that is buries into the pit in the ground, connected by PVC pipes that carry the water runoff into the hole.

Such dry wells are more voluminous and therefore can collect more water.

Simple Dry wells can be fairly easy to install but the large ones can be a bit of hassle. However, if installed properly, they can save a lot of future trouble and of course – money!

Before you get going with the installation process, it is always recommended to carry out a Percolation Test to check the absorption rate of the soil.

That test will determine whether it is suitable to build a drainage system, especially in case of a large dry well. Once things are in order, you can begin with the installation.

Dry wells are normally build at least10 feet away from a building’s foundation because otherwise, the water distributed into the ground may cause costly damage to your house.

For instance, the floorboards may start to warp and perish quickly. Depending upon the amount of water you are willing to hold, they can be up to 50 feet deep.

What Is A French Drain?

french drain

A French drain, named after US-based agriculturist Henry Flagg French, is a method that is in use since the 1990s to help with drainage problems within the property.

It is a ditch with pipes fit inside and filled with gravel that carries surface water from your house or the surrounding to an endpoint where the water is eventually collected.

The installation process is fairly simple.

You should begin with digging a ditch in the lowest point in the ground with a slope in the direction you want the water to flow, placing a perforated pipe in the ditch, and covering the ditch with a generous amount of gravel to keep the pipe in its place.

The idea is that whenever there is a flood situation, the water runs into these ditches, and as this happens, it starts entering the pipe from the porous side, which is placed facing downwards.

Once this happens, the water runs through the pipes, down the slopes and reaches a point where they are ultimately held.

Differences Between Dry Well And French Drain

dry well vs. French drain

It is true that both Dry Well and French Drain are effective ways of managing a waterlogged lawn; they are definitely not the same. 

The main difference between the two is that A French Drain collects excess water from within your building or from the surrounding areas and leads them to a single point, typically below ground level.

Their job ends when the water is accumulated in one place. And a Dry Well, on the other hand, holds the excess water and disperses them in the soil over time.

Here are some other differences that would make things clearer-

  • Prevention V/S Curative

A dry well cannot soak in excess surface water from an already flooded yard, Instead, it typically collects runoff water from drainage systems.

For instance – rain water from downspouts, or waste water from households from drainage pipes, or even water from a French Drain.

Therefore, Dry Wells help prevent having a swampy yard that could have otherwise happened if the water from these drainage pipes ran straight into the yard.

A French Drain, on the other hand, is designed to collect water excess surface water from a large area and carry it to a single place.

French Drains are therefore a great way to get rid of a flood within or outside your house.

  • Functional Differences

A French drain collects surface water and directs the water to an endpoint where it is eventually accumulated. The job of a French drain ends when the water is collected at a single point.

However, a dry well not only collects the runoff water, it also holds the water till it is distributed in the soil underground.

  • Percolation Tests

Percolation tests are crucial before the installation of dry wells because the effectiveness of dry wells depends upon the absorption rate of soil they are placed in.

This is because dry wells are meant to disperse the water into the soil in order to prevent flooding.

However, the absorptivity of soil differs across the types of soil. Clay soil, for instance, has a lower absorptivity and therefore may lead to a soggy yard if a dry well is built there.

In case of French Drains, however, percolation tests are not required since no distribution of water underground is involved in the process.

  • Environmental Concerns

Dry wells MIGHT lead to the contamination of ground water including drinking water, which has spurred a lot of concern regarding whether it is actually safe for the environment.

However, the US EPA labels a dry well to be safe if – the storm water or wastewater that it collects and disperses into the soil are not contaminated and if proper pretreatment is used.

In case of French drains, however, such concerns are not there.

  • Determining an End Point

In case of a French Drain, it is important to determine a proper end point where the water will be collected. It could, for instance, end in ponds, and drains, or even in dry wells.

While deciding the end point, it should be kept in mind that the runoff water does not impact some other property.

So, the best thing to do is to end the French drain in dry wells to manage the water well. Ending points, however, is not a concern for dry wells

Therefore, although both are drainage systems, a dry well and a French drain are not the same. Due to their difference in functions, structures, and usage, a dry well and a French drain are, in fact, often used together.  

A French drain is built to collect runoff water from a large area and to carry the water to an endpoint, where a dry well is installed to receive the water from the French drain and release them into the soil over time.

Once you have successfully installed a French drain or a dry well, or both for the matter, you can breathe out a sigh of relief really since you no longer need to worry about having a flooded yard or a place to dispose off the water.

Moreover, it is also not required to invest a lot of time and money into maintenance.

However, from time to time, you might want to check into the pipes and into the perforated chambers for any accumulated debris that could cause clogging.

You can consider using filters at the mouth of your gutters and drainage pipes to prevent debris from getting in in the first place.

Remember, if clogging happens, there is nothing to do but to rebuild the French drain or dry well.

Frequently Asked Questions (FAQs)

Does a French drain need a dry well?

French drains do need an ending outlet, which does not necessarily have to be a dry well.

However, if you so not have a suitable place to end the French drain such as a water garden, or a decorative pond, it is better to build a dry well at the end of the French drain.

Do Dry Wells Really work?

Here is the thing – A dry well manages drainage issues by collecting water and releasing them slowly into the slowly.
Diffusing water into the soil is not a very quick process and so, if there is more water than the capacity of the Dry well, there might be an overflow.

How deep should a Dry well be?

There is no set rule for the height of a dry well, it can range anywhere between 7/8 feet to some 5o feet, depending on the amount of excess water that is generated and is to be held by the well.

Can you end a French Drain underground?

Not really. French Drains are designed to end in an above the ground point, and that is why it typically ends in places that might collect water. Like a dry well

Can a Dry well cause a sinkhole?

Sinkholes or the sinking of the ground surface often results whenever the underground water levels change.
Since a dry well lead to the changing of water in the soil under the surface, yes, a dry well can often cause a sinkhole.

Does a French Drain work in clay soil?

Although clay soil is not particularly good for drainage, it is not as big a concern for French drains as it is for Dry wells where releasing water in soil is involved.

However, the strength of clay soil, especially when damp is low, which requires some extra caution while installing the French Drain.


To conclude today’s lesson on dry well vs. French drain, we can say that investments in preventive measures are definitely far better than spending on a damaged property.

Besides, while dry wells are French drains have their own differences in terms of functionality, the question is not whether to use dry well or French drain. These would rather be used in unison for more effective results and to save your property in the process.

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