Rain Water Collecting System FAQ

People are very interested in what we do and have a lot of questions - which we love answering! We’re passionate about designing and installing custom rainwater collection systems, but sharing our knowledge is also one of the best parts of the job.

This rainwater harvesting FAQ was made for anyone who's interested in any aspect of capturing rainwater for use at a home or business. If you have a personal question about rainwater harvesting systems give us a call and we'll give you an answer!

Q: Is collected rainwater safe?

A: Yes! Rainwater that is coming straight from a cloud to a metal or clay roof is very safe. That's why we collect rainwater from the roof, not the ground. Surface runoff harvesting, or stormwater collection, is only recommended for irrigation (if that) and other uses where the water won't possibly be consumed.

Rainwater harvesting systems can also be equipped with a first flush diverter, filtration unit and disinfectant system to remove impurities and contaminants. Treated water is just as clean, if not cleaner, than municipal water.

Q: Can I drink harvested rainwater?

A: It's possible, if the rainwater has been treated. This is called potable water. Some people actually prefer drinking rainwater because of the softness and taste.

If the intended use of a rainwater collection system is for drinking, it needs to be designed with filtration in mind.

Q: What can collected rainwater be used for?

A: That depends on how the rainwater harvesting system is designed and if it has a filtration system. With the right filtration, rain that's collected in a storage tank can be used for anything that you would use tap water for, including as drinking water.

Here's a quick list of how you can use harvested rainwater:

  • Drinking
  • Cooking
  • Bathing/Showering
  • Washing clothes
  • Watering a lawn and plants
  • Washing your vehicle
Q: What is rooftop rainwater harvesting?
A: It's a lot like it sounds. Rooftop rainwater harvesting refers to the process of capturing rainwater that falls onto a roof of a building or structure. The captured rainwater is either diverted to a filtration system or you can store rainwater in a tank.
Q: What considerations and provisions do I need to make and when, if I'm building a new house?

A: In terms of when, the sooner the better! The most common considerations for a rainwater harvesting system are:

  • Intended use
  • Tank placement
  • Roof type
  • Elevations
  • Pump and filtration location
  • Electrical needs
  • Guttering requirements
  • Plumbing configurations in the house (or existing plumbing if its already in place)

We can work with your architect and/or builder to ensure that the provisions for your rainwater system are in place.

Q. How much rainwater can I collect from my roof?

A: Rainwater storage capacity is going to depend on the size of the storage container. Rainwater tanks can hold up to 65,000 gallons of water.

In terms of how much rainwater you'll collect after it rains, that can be calculated for a fairly accurate estimate. You can collect approximately 0.6 gallons per one square foot of roof per inch of rain. For example, a 2,000 square foot roof will collect approximately 1,000 gallons from 1" of rain.

Q. What type of roof is required for rainwater collection?
  1. A: For a potable water supply, a metal, clay tile or cement tile roof is required. These are considered suitable roof materials for a catchment surface because they don't contain harmful toxins that can contaminate the rain water as it moves across the roof surface. For example, asphalt roofing wouldn't be an acceptable roof surface if you want to harvest rainwater for drinking.

However, keep in mind some cement and clay tile roofs may not be ideal if they leach minerals. Also, the roofing shouldn't be coated with another material.

If you are collecting rainwater for irrigation or non-potable use, any roof type could be acceptable.

Q. How many gallons of rainwater do I need to collect to sustain my household year round?

A. How much water you need to have in a storage tank is a different question. The average person consumes between 30 and 50 gallons of water per day, or 1,500 gallons per month. The trick is to have enough storage capacity to last through the "dry season", which is about three months out of the year in Central Texas.

Q. Why should I collect rainwater?
  1. A: There are a number of benefits for rainwater collection. First and foremost would be the excellent quality of rainwater. With no hardness or dissolved minerals, it is the perfect water by many measures. Another key benefit when you collect rainwater is the peace of mind in having your own self-sustaining water supply that is easily accessible to you and your family.

Lastly, when you harvest rainwater you're helping the environment. Water conservation through rainwater harvesting just makes good sense, but you'll also help reduce energy use. The more you harvest rainwater the less water the municipality has to treat and pump, which conserves energy.

Q: What is a rainwater storage tank made of?

A: Storage tanks for water collected through a harvesting system can be made from various materials. Knowing what the storage tank is made of is extremely important given that it impacts what the collected water can be used for.

Storing rainwater in a galvanized steel tank is highly recommended for potable water. Galvanized steel has a zinc coating that makes the steel more corrosion resistant.

Storing rainwater in a plastic tank isn't advisable for a few reasons. Plastic tanks don't have as long a lifespan and they are more likely to have algae growth. Fiberglass is considered to be a much better option than plastic.

Q: What is necessary for harvested rainwater to be considered drinking water?

A: First, the roof surface will make a difference. Only clay, concrete and metal roof surfaces are suitable for a potable system. But even then clay and concrete roofs may not be best because it could still leach contaminants. It's also important that the rain falls only on the roof surface to avoid contamination.

For harvested rainwater to be drinkable, or potable, you'll also need to treat the water. The first way to purify rain water is to have a first flush diverter installed that will divert the first bit of collected rainwater away. The first gallons are more likely to have dust, debris and other contaminants that were on the roof. This process is also beneficial because it reduces contaminants in the pump and piping while also making filtration easier.

As the rainwater moves through the harvesting system there are also ways to purify the water. The tank inlet should be equipped with a screen to prevent particles from entering. In-line cartridge filters can also be used to clear contaminants before they reach the pump.

The rainwater can then be sent through a filtration unit with a UV disinfection system. Filtration typically consists of cartridge sediment filters and active carbon filters. Once water passes through the filters it goes through a glass tube that is illuminated by UV light, which is known to effectively disinfect water.

Q: What is the water quality of rainwater?

A: The water quality is going to depend on a number of factors, but generally it's fairly clean. However, air pollution can hurt the quality of rainwater. Rain could also contain bacteria, parasites or chemical contaminants, which is why you always want a rainwater collection system with adequate filtration if you want full use of what's collected. You also need to inspect water tanks every so often to ensure the tank is clean and prevent algae growth.

Q: With a rainwater collection system would I need municipal water?

A: Since we can't control the weather, it's always advisable to have a backup water supply even if the rainwater harvesting system is designed to meet your needs and it regularly rains enough to meet your water supply requirements. If you're already hooked up to municipal water, you may want to maintain your account as a backup. If you're building a new home and want to eliminate the need for tap water from the city or county, look into the possibility of a well. In some areas, water delivery may also be an option in case there's limited rain.

Q: What are the steps for constructing rainwater harvesting systems?

A: The first step we take to construct a rainwater collection system is to do a site inspection. There are a lot of variables from the slope to tree coverage that have to be considered when you're harvesting rainwater. We also want to ensure rainwater tanks and other system components are integrated with existing structures.

Next comes the planning phase of the rainwater filtration and storage system. We'll come up with a design that meets the clients needs, which requires some careful calculations. During this phase we'll figure out all of the components that are needed.

Finally we move on to the construction of the rainwater harvesting system. This typically includes the:

  • Roof
  • Gutters and downspouts
  • First flush diverter
  • Storage tank
  • Pump

If you are harvesting rainwater to use inside the home there are a few extra steps that have to be taken. Pre-tank filtration components (first flush diverter and filter screens) need to be installed along with a filtration unit and UV disinfection system.

Q: How long can harvested rainwater be kept in storage tanks?

A: The harvested rainwater can be stored indefinitely under the right conditions, with a proper system setup and maintenance. We help property owners install rainwater harvesting systems that are capable of long-term storage so that clean water is available whenever it's needed. This is highly advantageous given that the Hill Country can experience dry weather.

Q: Can a rainwater harvesting system help with stormwater runoff?

A: Yes, a rainwater harvesting system reduces stormwater runoff. Instead of gallons of rainwater flowing through gutters and downspouts out into the yard or free flowing, you have control over exactly where the water flows and can optimize water usage.

Another ecological benefit is less runoff pollution. When you capture rainwater there's less rainwater runoff that can spread pollutants, pesticides and toxins.

Q: Can I really conserve water if it doesn't rain much in a year?

A: Harvesting rainwater is considered water conservation regardless of how much is collected. Every drop that you capture is a drop of tap water that doesn't have to be used.

Q: Will I still need a municipal water supply if I have a rainwater collection system?

A: Not necessarily. However, you'll need to check the local codes and regulations. Typically, it's possible to have a potable rainwater harvesting system along with a well. If a well isn't possible, then you may need to have a municipal water supply. How much rain you have in a year does need to be considered if you're trying to be completely independent of municipal systems.

Q: Will a rainwater harvesting system eliminate water bills?

A: It can. If you have a large enough rainwater storage tank, enough rain and a well for backup you can be 100% off-tap. But if you're hooked up to the municipal water as your backup supply you may still have a monthly bill for the general account charges that are in addition to water usage.

Q: Are rainwater collection systems regulated?

A: The use of rainwater collection systems is often regulated to some degree by the local municipality. There could be regulations regarding the use of captured rainwater, the size of the tank, the design of the rainwater collection system, installing underground piping, how runoff is diverted, etc.

Some states have also created regulations for harvesting rainwater. In those states, rainwater is considered the property of the state. If you want to know if rainwater collection systems are regulated in your state use the Department of Energy's Rainwater Harvesting Tool. The tool can also give you an estimate for rainwater harvesting potential.

Q: What happens to excess rainwater if my tank is full?

A: Collecting rain might prove to be easy during some seasons or years, and soon the storage system is at maximum capacity. When the average annual rainfall is higher than normal and your tank is about to overflow there are several things that could happen depending on how the rain collection system is set up. The excess water could:

  • Be diverted to a stormwater system
  • Flow into the sewer system
  • Be captured and sent to a filtration unit

If you think it could be an issue, discuss how overflow will be handled with the person who is designing the rainwater collection system. Some professionals feel that a little overflow in rainwater tanks is actually beneficial because it will help remove any floating particles and promote oxygenation.

Q: What should I consider if there are freezing temperatures?

A: The rainwater collected in your tank shouldn't freeze, however there are other issues to watch out for. The pipes of the collection system can be damaged if the water inside freezes. Likewise, the pump can also be damaged by freezing temperatures. Underground piping should be fine so long as the piping is below the frost line, but anything above ground should be insulated to prevent freezing. If you expect the freeze to last and have a backup water supply, you may want to consider winterizing the system.

Something else to watch out for is ice dams on your roof area that can prevent rainwater from flowing into storage tanks.

Interested in Having a Rainwater Collection System of Your Own?

Are you ready to be less reliant and more self-sufficient with your water usage? Now that you understand the basics of a rainwater collection system, let's discuss the details for your project!

Contact our rainwater harvesting experts at 830-347-8855!