The Ultimate Guide to Dry Wells

Water damage is a problem that can cause a variety of problems. This is why having an efficient rainwater drainage system is important for every property.

The goal of an effective rainwater drainage system is to get the water away from the property as quickly and efficiently as possible. Otherwise, you could end up with a wet basement, foundation damage, or even worse.

Anytime rainwater pools near your property, it should be taken seriously because it can cause damage even if it has passed through the ground.

The water around your property not only causes water damage in the form of leaks and mold growth. But it can also erode your foundation, causing it to shift, crack, or sink over time.

Most properties have some kind of rainwater drainage system in place to divert stormwater away from the building’s rooftop. Typically, this system consists of a series of gutters and downspouts that either discharge water near the house or convey it to a designated storm sewer.

If your rainwater drainage system sends the water that falls on your roof to a designated storm sewer, you mostly don’t need a dry well.

However, if your drainage system isn’t designed to divert water away from your property and instead discharges it directly on the ground around your house, you can greatly benefit from installing a dry well.

Because water that infiltrates near your foundation will always find a way to get in. This is where a dry well can be useful in intercepting and diverting it away from your home.

What is a Dry Well?

A dry well is a man-made water detention basin that collects, stores, and slowly discharges stormwater runoff. It is typically a perforated tank buried in the ground and connected to a building’s stormwater drainage system, which collects rainwater from the roof.

A dry well is usually filled with gravel or rocks to allow water to slowly filter through and reach the surrounding ground.

The time the water spends in the dry well allows pollutants to settle out, and the filtered water is then slowly discharged into the ground.

Because the dry well allows collected stormwater to seep into the soil, it also aids in the reduction of erosion and sedimentation.

During a storm, water that falls on the roof will flow through the gutters and downspouts until it reaches the dry well. Because the dry well is perforated with small holes, only a portion of the water can pass through at any given time.

This gradual release of water into the soil keeps the flow from rushing directly towards the building foundation.

What are the benefits of a Dry Well?

A dry well is a great way to keep groundwater from infiltrating your property. They are inexpensive and simple to build, and they do not necessitate a large amount of space or initial investment.

Most dry wells require some excavation to make room for the dry well tank or bucket and the connection to the downspout. However, they can be installed quickly by a qualified contractor.

Here are the most important benefits of a dry well:

Help prevent basement flooding

The collected stormwater is released into the ground over time, which greatly reduces the amount of water that can potentially enter your basement as a result of intense rainfall.

By directing the collected rainwater away from your foundation, dry wells can help to prevent flooding and other costly water damage like mold and mildew.

Reduces stormwater runoff

Dry wells can assist in mitigating the negative effects of stormwater runoff on streams and rivers. The water collected by the dry well is slowly released back into the ground, reducing the amount of runoff in the stormwater.

Prevents groundwater infiltration

Preventing groundwater from infiltrating a property can help reduce the risk of flooding, soil erosion, and foundation damage.

A dry well can be an effective way to achieve this, by intercepting and diverting away water before it has a chance to cause structural damage.

Reduces erosion and sedimentation

The gravel or rocks in the tank of a dry well help to filter the water as it is slowly released into the soil.

This helps to prevent erosion and sedimentation by giving pollutants in the water time to settle out before it gets discharged back into the ground.

Helps stabilize soil

The gravel or rocks that are used as a filter system inside the dry well allow for water to slowly seep into the soil.

This can help to stabilize and increase organic material in an area that is prone to erosion, making it a good tool for preventing excessive soil loss.

Provides groundwater recharge

One of the benefits of dry wells is that they help to replenish groundwater resources.

This is done by slowly releasing water into the surrounding soil through a series of gravel layers. Groundwater recharge with dry wells is especially useful for reducing demand on local surface water resources such as rivers, and lakes.

Dry wells may also be used to return water to aquifers by percolating the water through soils with a high water table.

This can help to replenish local groundwater resources and promote water resource security by mitigating the effects of drought and groundwater over-extraction.

Prevents waterways from contamination

Capturing urban rainwater prevents contaminants from entering waterways which can harm the local ecosystem.

Additionally, the slow release of water into the ground also helps to reduce erosion and runoff that can lead to sedimentation in nearby bodies of water.

What are the important considerations of having a Dry Well?

While there are many benefits to using dry wells, they aren’t always appropriate for every site.

Here are a few things you should keep in mind when deciding if a dry well is a right solution for you:

The slope of the drainage system

The slope of your drainage system will affect how well a dry well function. In order for a dry well to work properly, the water needs to be able to flow freely into it.

Therefore, installing a dry well requires calculating the grade of your drainage system to ensure that the water will be able to move towards the dry well.

Generally, water should be able to move without using a mechanical device. However, if your drainage system is not built with a sufficient slope, you may need to use a pump or other device to get the water to the dry well.

Water table level

If you live in an area where the groundwater is high, then dry wells are unlikely to be effective at preventing infiltration into your foundation.

Because the water table will be high, the area around the dry well the soil will be saturated and unable to absorb any more water.

Distance from the foundation

The closer a dry well is to your foundation, the more likely it is that groundwater will infiltrate your property.

If you are considering installing a dry well, make sure to place it in an area that is as far away from your home as possible.

To reduce the risk of basement seepage or flooding, a distance of 10 feet between the dry well and the building foundation is recommended. If the separation distance is less than that an impermeable liner may be required on the building side of the dry well.

Size of the dry well

The size and number of dry wells that you need will depend on the size of your property. Because a larger property will also collect more water, you will need more dry wells or a higher capacity one to properly prevent groundwater infiltration.

If you have a property that covers more than two acres, you may consider having multiple dry wells in order to effectively prevent groundwater infiltration.

Maintenance requirements

Dry wells require regular maintenance in order to keep them functioning properly. This includes removing any debris that may have been collected in the well and keeping the filter system clean.

If you are not able to maintain your dry well, it will cease to function and you will see an increase in groundwater infiltration.

Proximity to the water bodies

If you live near a river or large body of water building a dry well may not be as straightforward as it seems.

Because areas that are near water can already have a high level of groundwater, building a dry well in this area may not help to prevent groundwater infiltration.

A dry well that is not calculated well enough can act as a drain and pull water away from the natural waterway.

If you live by a river or another body of water and still want to build a dry well, then you should contact your local municipality and/or qualified contractor to discuss your options.

Make sure that the area and installation meet all regulations and requirements in order to prevent groundwater contamination and flooding into nearby bodies of water.

How to maintain a dry well?

Regular maintenance is essential for keeping a dry well functioning properly. Some of the most important things to keep in mind are:

Checking for debris

Dry wells function best when they don’t have any blockages or clogs, so you should check your dry well once a month to make sure it’s not collecting any sticks or leaves.

If there is anything blocking the flow of water into the well and from the well, you may need to remove it.

Checking the filter system

The dry well’s inlet and outlet filters should be checked every month as well. Make sure they are clean enough that water is able to continue moving through them without being slowed down or stopped by any debris stuck inside of the filter material.

If there is a lot of debris in the filters, you will need to clean them more often.

Gutter inspection

Gutters are an important part of a drainage system and should be checked every few months to make sure they’re not clogged or blocked.

If the gutters are not draining properly, water will not be able to move to the dry well and it will not be effective in preventing groundwater infiltration.

After a storm, inspect your gutters to ensure that rainfall drains properly to the dry well.

Notify other contractors

Buildings have various systems that need to be in sync in order for them to work properly.

If you are having contractors of different systems working on your property make sure to notify them of the existence of the dry well, and its location so that they can take it into account when working.

Install gutter guards

Gutter guards can help to keep debris from clogging the gutters and prevent proper drainage. To filter leaves and sediment from rainwater before it reaches the dry well, install gutter guards or screens on top of roof downspouts.

Also, a roof leader clean-out with a sump or an intermediate sump box can be installed between the downspout and the dry well, lowering the amount of sediment and debris entering and potentially blocking the dry well.

If you are unable to maintain your own dry well, there are professionals who can help with the maintenance. Make sure to contact your local municipality or a qualified contractor to inquire about their services.

Observe dry well’s condition

Observe the condition of your dry well and the surrounding area. If you see it cannot drain water even long after a rainfall event, it may be necessary to contact a professional to help fix the problem.

Because you don’t want to allow the dry well to overflow into your building’s foundation.

No mowing around

Do not mow the grass around your dry well. Doing so will disturb the soil as well as move the observation well cap from its original location. The well cover should be in place to prevent debris and critters from entering the well.

Place no structures on top of the dry well

A dry well should not be covered by any structures, including but not limited to decks or other structures.

Keep children away

Never let children near a dry well or seepage pit without adult supervision. Dry wells and seepage pits can be dangerous, especially if they’re uncovered.

So please be sure to keep kids away from these areas and always have an adult present when they’re in the vicinity.

What is a dry well alternative?

French drains prove to be a good alternative for areas that are not suitable for dry wells. They dispose of water away from the place to an open area. Contrary to French drains, a dry well disposes of water evenly underground.

How do dry wells function in clay soil?

Dry wells are ineffective in clay soil. Because clay soil does not allow water to pass through causing the drainage becomes a serious issue. Dry wells in clay soils tend to pool water or a pond.

What are the signs that the dry well pipes are going to freeze?

Lowered water pressure or no water coming out of the facet give the alert. Running warm water helps in defrosting. Similarly, holding a hairdryer near the pipe wall will also work. In extreme cases, cut the pipe from the area and give direct heat. 

Is a dry well legal?

Many cities have regulations around if and where you can build dry wells. So, it is important that you check with your local municipality or county to see if dry wells are allowed in your area.

What is the difference between a Dry Well and a Septic Tank?

Dry wells are primarily used for drainage, while septic tanks treat and dispose of wastewater. A dry well should not be used as a replacement for a septic tank.

Septic tanks require regular maintenance, including pumping out the sludge and solids that build up over time. If these are not removed, they can eventually clog the tank and pipes, causing wastewater to back up into the home.

Dry wells do not require much maintenance but should be inspected periodically to ensure that they are functioning properly.

Can a Dry Well freeze?

Drywells rarely freeze because they are not located above ground. However, if the well is located close to the ground and/or has inadequate insulation, the water in the well may freeze when the outside temperature falls below freezing.

Planning a dry well for your property make sure it is installed below the frost line to avoid freezing in cold weather.

What to do when dry well drains freeze?

If the water in the dry well freezes, thaw it out with a hairdryer or heating pad. If the water does not drain after several hours of defrosting, you may need to cut the pipe and use a heat gun or torch to melt the ice.

If you have a dry well that is prone to freezing, you can insulate the pipe with foam insulation. You can also use heat tape to prevent the pipes from freezing.

How deep should a dry well be?

A dry well should be installed at least 12 feet below the ground to ensure that it can effectively drain water to a safer location.

Shallow installed dry wells tend to leave the water at a higher level, increasing the risk of water propagating to the property. As a general guideline, the bottom of the dry well should be at least 2 feet above the high water table or bedrock.

In what soil conditions should dry wells not be used?

Dry wells are typically ineffective in clay soil as it does not allow water to pass through easily.

The well appears as a pool of water or a pond if clay soils are present around the house. Therefore, before installing a dry well, it is important to have your soil tested to see if it is suitable for a dry well installation.

Can a dry well be used to collect greywater?

Yes, a dry well can be used to collect and disperse greywater from the home. However, before installing a dry well, it is important to check with your local municipality or county regarding laws and regulations.

Because the definition of greywater and the regulations around dry wells are different in each location. Therefore, contact your local authority to see if a dry well is an option for greywater collection in your area.

Can you pump out a dry well?

Yes, you can pump out a dry well. For certain reasons, you may need to remove the water from the dry well. This could include pumping out the water after a heavy rainstorm to prevent flooding or if the dry well is clogged and not draining properly.

If you need to pump out the water from your dry well, you can use a submersible pump to remove the water.

Can a dry well cause a sinkhole?

A sinkhole can form when the water in a dry well erodes the soil around it, creating a hole in the ground. This is more likely to happen if the dry well is installed in a location with sandy soil.

It is important to monitor the condition of your dry well and surrounding soil to ensure that there is no risk of a sinkhole forming. If you see any signs of erosion or sinking around the dry well, contact a professional immediately.

Do dry wells smell?

Dry wells do not typically smell because the water is dispersed underground. However, if there is an issue with the drainpipe or if the well is clogged, you may notice a bad odor coming from the dry well.

If you smell a bad odor coming from your dry well, contact a professional immediately to find and fix the source of the smell.

How much cover is necessary on top of a dry well?

A dry well’s top should have a minimum of one foot of cover to ensure that the well is properly placed and that the soil is properly compacted.

You can place a variety of materials on top of a dry well, such as sod, gravel, or crushed stone. It is important to keep the cover material level and free of debris to prevent clogging.

Do I need a permit for a dry well in my area?

Depending on your location, you may need a permit for the dry well. It is important to check with your local municipality or county before installing one to ensure that it meets all regulations and laws.

Can I use gravel around my dry well?

Yes, you can use gravel around the outside of the dry well as an added layer of protection. The gravel will help to keep the soil in place and prevent erosion around the well.

What is a dry well ring?

A dry well ring is a perforated cylinder that makes up the side of a dry well. It is coupled with top and bottom caps to create the entire dry well structure.

Do dry wells overflow?

A dry well is built to detain water and allow it to disperse slowly. However, depending on the size of the dry well and how much water is being collected, it could overflow.

How fast should a dry well drain?

The drain time is the amount of time it takes for the dry well to empty or the rate at which water drains from the well. We expect most dry wells will drain and empty within 72 hours of a rain event.

Otherwise, it may cause mosquito problems or other health issues. The permeability of the soil and the surface area of the dry well where the water will be drained determine the drain rate.

If the drain time is longer than 72 hours, the dry well’s bottom area must be expanded to allow more water to drain into the soil. It is an effective strategy to increase the size of the bottom surface in order to reduce the dry well’s height.

Should you have a filtering screen installed to a dry well?

Yes, to screen out leaves and other debris a filtering screen should be installed in the bottom of the gutter below the surcharge pipe.

Do dry well need access pipes?

Yes, dry wells need access pipes to allow for inspection and cleaning. The access pipes should be large enough to accommodate a comfortable working when doing maintenance work.

Do dry wells have overflow pipes?

Yes, properly designed dry wells have an overflow surcharge pipe or link to a bigger infiltration area is required to ensure that additional runoff is securely carried downstream during a strong storm event that overflows the dry well.

How to calculate the required volume for a dry well?

The required volume of the dry well is the same as the runoff volume if you use a prefabricated tank that does not include gravel.

Because the rock takes up so much room in a gravel-filled dry well, there is a significant reduction in the effective storage capacity of the well.

Because about 40% of gravel is air or void space, only approximately 40% of the volume of a dry well filled with gravel can store water.

So if you have a dry well with an effective storage capacity of 100 gallons, only 40 gallons will be available for stormwater detention.

To determine the volume of the dry well, divide the runoff volume by the 40% void space. If you have a material with a different void space, substitute that value for the 0.40 in the equation below.

Dry well volume (cuft) =  runoff volume (cuft) / 0.40

How to calculate the dimensions of a dry well?

The dry well box’s dimensions will be determined by the dry well’s total volume. The volume is calculated as the height times the length times the width.

The box’s height may be a limiting factor by the depth to seasonal high groundwater or bedrock and the need to cover the dry well by approximately 1 foot.

The dry well’s bottom must be two feet above the seasonal high water table. A dry well for a residential home normally has a height of no more than 48 inches, even if groundwater or bedrock isn’t a concern.

Height = Depth to SHWT or bedrock – 3′

(3′ –> 2′ for separation to SWHT or bedrock + 1′ for cover on top)

The volume of the dry well is calculated as follows: The height is multiplied by the length, which is then multiplied by the width.

Volume = Height (ft) × Length (ft) × Width (ft)

How long does it take to install a dry well?

The time to install a dry well greatly varies on the size of your property, whether you are digging new trenches or using an existing one, and the size of the trenches.

Deeper and wider trenches take longer to install a dry well than shallower and narrower trenches. If the trenches are dug and the dry well location is ready, a qualified contractor should install it the same day.

If a dry well is being built from the ground up, it should take about a week, depending on the contractor’s skill, manpower, and weather conditions. This estimate does not account for the permit process, which may lengthen the entire process.

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