In this guide

Uses of Harvested Rainwater

Collected rainwater can be used for watering lawns and landscaping, and it can also be treated and used to supplement your municipal supply by using it for washing machines and other in-home uses. In some cases, where the law allows, you can even treat rainwater and use it for drinking, but many areas do not allow this practice.

Stored rainwater can also be used for toilet flushing and taking showers, and in some cases, when using a first-flush system, rainwater may also be used for bathing. To ensure the water is safe for these household purposes, it is vital to keep it away from light and contaminants and use a strong filter in your rainwater system.

The way a rainwater collection system works is by consolidating rainwater from rooftops. Rainwater systems redirect water from gutters and downspouts and hold water in a storage tank. The system has some form of distribution, which can be as simple as a spigot and hose and as elaborate as a full irrigation system that’s integrated into the municipal supply.

An average household rooftop is about 2,000 sq. ft. Annual rainfall varies dramatically based on where you live in the country, but you can expect to collect about 0.62 gallons of rainwater per square foot of rooftop per inch of rainwater. Look up your area’s average annual rainfall to determine how much rain you might collect during the course of the year.

Rainwater Collection System Costs by Method

There are two main methods for harvesting rainwater: rooftop rainwater harvesting and surface runoff harvesting. These methods work differently, but both involve collecting and storing rainwater for reuse, rather than simply letting it run off and drain away.

Rooftop Rainwater Harvesting

Rooftop rainwater harvesting is focused on collecting rainwater directly from the roof. It uses the roof as a catchment device, letting water land on the roof panes, flow into the gutters, and then is redirected into a tank. This method is much cheaper than surface runoff harvesting and costs between $1,000 and $5,000 on average.

Surface Runoff Harvesting

Surface runoff harvesting focuses on collecting runoff rainwater. This means letting the rain fall on the ground and then having it flow into a tank, which is usually situated below the ground. Unlike with a rooftop system, surface runoffs make use of the ground itself as the collection area for the rainwater. It flows along the ground and down into grates, where it enters underground pipes and flows into a tank.

In-ground surface runoff systems must be located at least 10 feet away from any watertight sewer line and 50 feet away from any non-watertight sewer line to avoid contamination. If you cannot work within those limits, you may have to stick with an above-ground system. A surface runoff system can have one grate or several, and since these systems involve a lot of digging and labor, the costs can be quite high, ranging from $8,000 to $15,000.

Rainwater Collection System Cost by Type

There are different types of rainwater collection systems, varying in capacity, function, and price. You can get very simple rainwater collection systems like barrels that sit out in the open and collect rainwater that runs off the roof, as well as much more complicated systems involving pipes flowing from the roof down underground into below-surface tanks. The most common rainwater collection methods make use of the rooftop harvesting method, and the table below shows three common types, along with a price range.

Rain Barrel

This is the simplest method for collecting rainwater. A rain barrel connects to a gutter downspout and usually has a cover and a spigot at the base for distribution. Raising the barrel above ground level will allow gravity to push water out. Rain barrels cost about $120-$160. Some people may worry that having big barrels sitting alongside their home could look unsightly, but these days, there are plenty of decorative rain barrels available. Some homeowners use them like outdoor furniture, painting the exterior and growing plants on the top to enhance the look of their rainwater collection system.

Dry System of Rainwater Harvesting

A ‘dry’ system is essentially a larger version of a rain barrel. A dry system uses a large storage tank that is placed close to the house for water to flow from the gutter pipes directly into the storage tank. This is called a dry system because the collection pipe is “dry” in between rainfalls, as the water flows straight into the tank. The largest portion of the cost of a dry system is the storage tank, which varies based on capacity and storage material. A 5,000-gallon polyethylene tank costs about $2,100.

The main benefit of a dry system is how simple it is. The pipes run directly from the gutters to the tank, emptying themselves in the process, with minimal maintenance required. On the downside, they involve the use of barrels or tanks placed very close to your home, which may be an issue for some homeowners. Dry rainwater collection systems cost between $1,000 and $5,000.

Wet System of Rainwater Harvesting

A wet system is much more complex than a dry system. With this type of system, the pipes are located underground, and all gutters eventually feed into this system. The pipes fill with water until there is enough to spill over into the storage tank. These systems are known as wet systems because the pipes remain filled with water at all times unless you empty them somehow. The big benefit of a wet system is that the pipes are hidden away, so they will not interfere with the aesthetics of your property. On the downside, the pipes can be vulnerable to issues like bug infestations and debris accumulation, so it requires good filters and regular maintenance.

Due to the need for underground piping, it costs significantly more than a dry system or rain barrel. Costs vary based on the amount of pipes that need to be laid, but expect to pay landscapers $45-$75 per hour for labor. For a 5,000-gallon ‘wet’ tank with a sprinkler system, you’ll pay $2,500-$4,500 for the irrigation and sprinkler installation (24-32 labor hours), $4,000 for a steel storage tank, $2,500-$3,000 for a water treatment system, and $440-$760 for three hours of excavator rental to dig the hole for the tank, which includes an operator. This comes to about $12,000, with the average cost of wet systems ranging from $8,000 to $15,000.

Labor Costs to Install a Rainwater Harvesting System

The tank seller may provide installation services, but certain landscapers may also be able to install these collection systems. An average project involves preparing the tank area, connecting the tank to the downspout(s), and connecting the tank to a pump and any pipes or exit points. Landscapers charge on average $45-$75 per hour. Installation time will vary based on the size and scope of your project. A sprinkler system and irrigation for a wet system will take 24-36 labor hours and will cost about $2,000-$3,400 just for labor. A wet system would also need excavation to bury the storage tank. You would need to pay for excavation equipment rental and an operator, and the project would probably take about 3 hours and cost $440-$760.

Installation Considerations

Before installing a rainwater collection system, you’ll need to consider what size storage tank you will need and the amount of space required for it. Your tank size needs will vary based on how much rainfall you have in your area and how much space you have on your land. A 5,000-gallon polyethylene 5 tank will cost about $2,100.

A dry system needs to be placed close to the house, but a wet system can be installed farther away from the building. Rain barrels should be directly underneath a downspout. Screens are not required, but they prevent debris and leaves from getting into your rainwater. Filters are not necessary if you are simply using your system for irrigation but are needed if you plan to use the rainwater for household use.

Irrigation systems 2 will add significantly to your costs. The location and elevation of the irrigation area relative to the rainwater collection system will impact the cost, but on average, an irrigation/sprinkler system will cost $2,500-$3,500.

Components of Rainwater Harvesting System

Every rainwater collection system has certain essential components, including filtration, a conveyance system, water storage, and a collection area. The prices for these components vary, depending on the size, type, and scale of your system, but the table below provides general estimates.

Filtration Cost

Filtration is not always necessary for a rainwater collection system, but if you plan on reusing the water around the home, it is essential to install a filter to rid it of bacteria and other undesirable elements. Filters vary in style and functionality but usually cost between $100 and $250.

Conveyance System Cost

The conveyance system of any rainwater collection system consists of pipes and fittings. The number and length of pipes required depend on the size and type of system you install. So, the price varies from as low as $100 for simple systems to $2,000 or more for more complex systems.

Water Storage Cost

The water storage component is one of the most expensive parts of a rainwater collection system. This can be anything from a simple rain barrel placed beside your house to a vast underground tank with a huge capacity. Since there are many kinds of water storage, the price range is broad, from $120 to $4,000.

Collection Area Cost

The collection area for a rooftop collection system is the roof and gutters, whereas the cost for a surface runoff system is the section of ground where you want the water to flow and enter the tank. The prices for these areas varies enormously, depending on the type of system, the topography of your property, and the size of your home.

Optional Components of a Rainwater Collection System

As well as the essential parts of a collection system, there are several optional parts to consider. These add-ons help improve your system in a variety of ways, from transporting the rainwater more efficiently to removing debris from the water as it enters the tank. The table below shows some optional components and their price ranges.

Gutter Mesh Cost

Gutter mesh can be installed onto your home’s gutters. It acts as a filter for large items like leaves and other debris, preventing them from flowing along with the rainwater and ending up inside your tank. Expect to pay about $6 to $10 per linear foot of gutter mesh, installed.

Gutter Outlets Cost

Gutter outlets, sometimes referred to as downspout connectors, are used to channel the water from the gutter into the downspout. Downspouts are recommended for every 20 feet of gutter, and every downspout needs a gutter outlet. They cost around $5 to $10 each.

Downspout Screens Cost

Downspout screens are fitted at the tops of each downspout and also serve as filters to prevent bugs, leaves, and other debris from entering the pipes or flowing into the storage tank. They are essential for rainwater collection systems where the owner plans to use the water in the home for things like bathing. They cost around $10 to $30 each.

Tank Screen Cost

Tank screens are fitted over the tank, at the lid, and filter out debris, leaves, bugs, and more. They are another layer of filtration to shield your collected rainwater from unwanted elements, and costs range from $10 to $30 each.

First Flush Diverter Cost

A first flush diverter is another essential add-on if you plan to use the rainwater in your home for bathing, drinking, or other uses. It is used to flush away the first layer of rainwater because it is usually quite dirty and filled with toxins and should not be used. A first flush diverter usually costs between $20 and $40.

Tank Gauge Cost

A tank gauge is another optional component you might consider if you plan on keeping a close eye on your collection system to ensure that it stays running smoothly. The gauge allows you to see the water level inside the tank at any time so that you know exactly how much water is in there. Tank gauges range from $30 to $50.

Top-up System Cost

A top-up system is used to automatically fill up the tank with water. This prevents the tank from dropping below a set level, and a top-up system usually costs about $100 to $200.

Pump Cost

A pump is used to distribute the water through the pipes, pushing it along and making it easier to extract or divert to certain areas or into the home. This makes it much easier to reuse your water, either inside or outside. Pump prices range between $150 and $300.

Benefits of Collecting Rainwater

There are many benefits to installing a rainwater collection system and collecting rainwater for your home, and these benefits apply to all kinds of rainwater systems. The first and most obvious benefit is that rainwater is free, so having a collection system lets you gather your own source of free water. Rainwater also does not contain any added chemicals or additives that may be found in municipal supplies, and this helps to make it much safer to use for landscaping and general gardening.

Collecting rainwater can save you money on your water bills too, as well as reducing the possibility of flooding if you live in a flood-prone area. Plus, with the right add-ons like filters and first flush systems, collected rainwater can be used in your home for all kinds of things like bathing and even drinking. There are a couple of downsides, however, because rainwater collection systems can be expensive and take up space around the home. Also, you can never predict when rain will fall.

How Much Rainwater Can Be Collected

The amount of rainwater you can collect with a rainwater collection system depends on the type and size of system you use. If you place a rain barrel beneath your gutters, you are limited to the maximum capacity of the barrel, which is usually about 50 to 60 gallons. If you want a much larger wet or dry system with a large storage tank, they are available in sizes from 1,000 to 15,000 gallons or more in capacity.

Also, the amount of rainwater collected depends on the size of your collection area. For each inch of rain that falls, about 550 gallons of rainwater can be collected for every 1,000 square feet of space. So, larger collection areas collect more water on average.

Rainwater Harvesting vs Greywater Recycling

Greywater recycling is another method of collecting and reusing water. This method involves recycling wastewater from home appliances like your washing machine or bath. The ultimate goal of both these methods is to minimize waste and promote recycling of water, but they differ greatly. Since it is collected from sinks and appliances, greywater is often filled with all kinds of chemicals and can include things like soap, detergent, and toothpaste, as well as human matter like hair and skin cells. Therefore, it is very unsafe in its unfiltered state and must be thoroughly disinfected and filtered. Even with cleaning, greywater is sometimes considered unsafe to be used on plants or gardens and is only really suitable for toilet flushing. If you want to use the water for things like bathing, drinking, or irrigation, it is best to opt for a rainwater harvesting system.

Rainwater Collection System Maintenance

Rainwater collection systems do require some regular maintenance. Gutters and filters need to be cleaned, and all components should be inspected to ensure that all parts are in proper working order. This is something you can do yourself or have an experienced landscaper come out and take care of. Landscapers will charge by the hour ($45-$75), and you should have your system checked every season. Visually inspect your system after any rain to ensure that filters are not clogged.

Enhancement and Improvement Costs

Sprinkler System

You may not want to deal with the hassle of watering the lawn yourself, which is why you may want to consider a sprinkler system. Adding a sprinkler system will add to your system costs. A standard, professionally installed sprinkler system for an 8,000 sq. ft. lawn averages $2,500-$3,500.