How to Collect Rainwater From Gutters

rainwater harvesting system in a house

Every time it rains, gallons of water come flowing down your gutters and out your downspouts. Instead of that rainwater ending up in a storm drain, you could be collecting it to use around your house. Knowing how to collect rainwater from gutters is just the start.

A big part of collecting rainwater is your gutter system. If it’s not in good condition, you can’t harvest stormwater effectively, so make sure your gutters and downspouts are in proper working order.

Collecting rainwater has a variety of benefits, such as saving money on your water bill, reducing your carbon footprint, and making your house independent of a municipal water system.

3 Rainwater Harvesting Systems

There are a few different ways you can collect rainwater, and each rainwater harvesting system has its pros and cons.

  • Rain barrels
  • Dry systems
  • Wet systems

Rain Barrels

water coming out of a drain pipe to rain barrel
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The simplest way to collect rainwater from your gutter system is with a rain barrel. Rain barrels are self-explanatory: You put the barrels beneath your gutter downspouts to collect stormwater and store it for later use. You dispense the water using a spigot that’s installed on the side. Rain barrels are a good system if you’re just starting out collecting rainwater or if you don’t want to deal with something more complicated.

Pros of a rain barrel system include:

  • Simplicity
  • Low-maintenance
  • Easy to install and move
  • Inexpensive

Cons of a rain barrel system include:

  • You may need multiple barrels if you get a lot of rain.
  • If a rain barrel overflows, the water may damage your foundation or basement.

Dry Systems

A dry rainwater collection system is more complicated than a rain barrel, but still follows the same basic principle. It’s essentially a plumbing system that has pipes leading from your gutters to a large storage tank, also called a cistern. Just like a rain barrel, it has a faucet on the side to dispense the water. 

The system is called “dry” because the pipes are at an angle above ground, which means that no standing water forms and the pipes eventually dry out.

Pros of a dry rainwater collection system include:

  • Easy to install and move
  • Pipes do not need draining
  • Inexpensive

Cons of a dry rainwater collection system include:

  • Unattractive design
  • Must be close to the building

Wet Systems

Wet rainwater collection systems are even more complicated than a dry system. Unlike a dry system, in which the pipes are above ground, the pipes for a wet system are buried underground. A wet rainwater collection system relies on water pressure, instead of gravity, to deliver the water from your gutter system to your water tank.

Wet systems get their name because stormwater runoff stays in the pipes after it finishes raining, so they’re always wet. This water remains there until it rains again and it’s pushed into the tank. If you don’t want water stagnating, you can install a first flush diverter that will flush it out so that it’s not just sitting in the pipe.

Pros of a wet rainwater collection system include:

  • Looks neater than other systems
  • The tank can be placed almost anywhere
  • Easy to connect different buildings

Cons of a wet rainwater collection system include:

  • More expensive than other systems
  • More difficult to install than other systems
  • Water in pipes is stagnant

Legality of Rainwater Harvesting

rainwater harvesting system with a tank
Photo Credit: SuSanA Secretariat / Flickr / CC BY 2.0

Before you can get started with water collection, you need to check your state’s rainwater harvesting rules. Some states have laws restricting or even outright forbidding the collection of rainwater.

Before you buy a rain barrel, check your state’s laws to see whether you’re allowed to collect rainwater, as well as how much and whether or not you need a permit.

How Much Water Can I Harvest?

Putting aside legal restrictions on the amount of rainwater you’re allowed to collect, there are still limits to how much rainwater you’ll get out of your system. Exactly how much you’ll get is dependent on the amount of rainfall in your area and your system’s capacity.

The typical formula for measuring the amount of water you’ll collect is this: 1 inch of rain over 1 square foot results in 0.623 gallons of water. In other words, if you have a 1,000-square-foot roof, you’ll get 623 gallons for every 1 inch of rainfall. Since most roofs are bigger than this by about half, you can expect to harvest quite a bit whenever it rains.

However, your rainwater harvesting system can hold only so much. The typical rain barrel holds between 50 and 90 gallons of water, so you’ll end up with a lot of excess even if you have multiple barrels. Make sure you have a good drainage system in place so that the extra water doesn’t end up seeping into the ground and causing you problems.

Benefits of Harvesting Rainwater

diagram showing how a rain harvesting system works
Photo Credit: Adityamail / Wikimedia Commons / CC BY 3.0

Harvesting rainwater has many benefits. It’s both environmentally and economically friendly, and while it can be difficult to set up at first, it’s worth it.

Here are some of the benefits of harvesting rainwater using your gutter system:

  • Save money: Harvesting rainwater should lower your monthly water bill.
  • Reduce your carbon footprint: Since water companies don’t have to use energy to treat water and send it to your home, it will create less carbon, which is good for the environment.
  • You’re less dependent on your municipal water system: If your municipal water systems get disrupted due to a storm or drought, it can spell disaster. Harvesting rainwater will both help you avoid this and ease some of the pressure on the public water system.

Uses of Harvested Rainwater

Harvested rainwater can be used for a variety of purposes. However, until it’s been put through a filtration system, rainwater can be used only for non-potable purposes, aka landscaping. Once harvested rainwater has been filtered and purified, it can be used for other purposes, such as: 

  • Bathing (you and your pets)
  • Cleaning
  • Drinking
  • Laundry
  • Water in toilet tank
  • Washing your car
  • Filling a pool

How to Maintain Your Rainwater Harvesting System

As with your gutters and just about any other home fixture you have, your rainwater collection system will need maintenance. You’ll need to clean your storage tanks periodically to prevent algae growth, sediment, mildew, or rust from forming. You also need to change the filters every so often to keep contaminants out of your water, and clean the pipes to prevent clogging and buildup.

To keep the water in your tank from getting stagnant, use the water often. Stagnant water attracts mosquitoes, which you do not want in your tank.

Aside from the above, all you need to do to maintain your rainwater collection system is to sweep your roof area and clean your gutters regularly. This will reduce debris that is caught in the filters of your rainwater harvesting system.

FAQ About Rainwater Harvesting

Are there any downsides to harvesting rainwater?

There are some drawbacks to harvesting rainwater.

First, you’re responsible for the maintenance and cleaning that’s required to keep your rainwater system working.

Second, the amount of water you collect is dependent on the amount of rainfall your area gets. If you don’t get enough to consistently meet your home’s water needs, you’ll have to subsidize it with tap or well water.

Is harvested rainwater safe to drink?

No. Rainwater is not safe to drink due to the presence of both bacteria and pollutants picked up when it falls onto your roof and goes through your gutters. Do not drink rainwater that has not been filtered and purified, or use it for purposes other than watering your landscape.

Is rainwater cleaner than tap or well water?

Until it falls to the earth, yes. Rainwater is pure in the atmosphere, but when it falls to the ground, it picks up debris, bacteria, chemicals, and other pollutants. This makes tap or well water the safer option.

Can I use a rainwater collection system in the winter?

Yes, you can, though you’ll need to take steps to ensure that it keeps running properly.

Here’s what to do:

Apply heat tape to the gutters and any above-ground pipes to prevent the water from freezing. The water in your storage tank may freeze, but only the top few inches. The water in the middle, where the pump should be located, will be unaffected. Any underground tanks or pipes don’t need any heating.

If you do want to shut down your rainwater collection system for the season, you’ll need to take some extra steps. Close any pipes and empty your storage tanks to prevent stagnation. In the case of rain barrels, store them upside-down in a secure place.

When to Hire a Gutter Professional

To recap, collecting rainwater isn’t always easy, but it can benefit you quite a bit if you do it right. Even if you just have a couple of rain barrels, you can save money on your water bills by gathering the water that flows through your gutters.

Note: Your gutter system needs to be in good working condition for your rainwater harvesting system to be effective. We can connect you to your local gutter professionals if you need help replacing an existing gutter system or repairing damaged gutters. 

And, of course, we can connect you to the best gutter cleaning pros near you, too.

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Austin Geiger

Austin Geiger is a writer who's passionate about home care. He enjoys writing about home maintenance practices, as well as projects to turn an outdoor space into a backyard paradise.