This fact sheet covers the basic components of a rain harvesting system, Utah\u27s laws for rain harvesting, how to estimate the volume of water storage you will need, ideas for increasing water pressure in your system, as well as tips and insights for building a rain harvesting system

Brain, Roslynn

Carter, Kohl

Cromwell, Shannon

Palmer, Matthew

DigitalCommons@USU

1Version: October 2015Rainwater Harvesting for the Home and FarmMatt Palmer, Kohl Carter, Roslynn Brain & Shannon CromwellSanpete County Extension & Department of Environment and Society Water use is an important issue in the west, and many people are interested in learning how they can use this resource more efficiently. While rain harvesting isn’t going to solve all of  our water use issues, it certainly is an impressive and effective way for individuals to take advantage of  the surprisingly large amount of  water that rolls off  of  their roofs every year. It may shock some people to find out just how much water their roofs are capable of  collecting. For example, on average Ephraim receives 5.33 inches of  rain from April to September.1 With this amount of  precipitation a roof  that is only 1,000 square ft. (25 ft. long and 40 ft. wide) is capable of  collecting 3,322 gallons of  rain over the course of  that time. That is roughly equivalent to sixty 55 gallon drums of  water which is enough water to grow a decent sized garden. This fact sheet will cover the basic components of  a rain harvesting system, Utah’s laws for rain harvesting, how to estimate the volume of  water storage you will need, ideas for increasing water pressure in your system, as well as tips and insights for building a rain harvesting system.Basic Components Although rain harvesting systems can vary both in terms of  style and complexity, the basic components are relatively simple. They are:• Catchment area: Intercepts the rain water and directs it toward the gutter system. This will most likely be the roof  of  a house, garage or other building.• Gutter System & Downspouts: Catch the water draining off  of  the catchment area and channels it into the storage containers. If  the roof  of  your house is your catchment area, the gutter system may already be in place, and you will only have to modify the downspout so that it channels the water into your storage containers. If  you are installing your rain harvesting system on a building that doesn’t already have a gutter system in place, then you can either buy a standard gutter system or you can get creative and build it from whatever you have lying around. For example, in Sanpete County Extension, we used 6 inch PVC pipe cut in half  to build the gutters on our turkey barn.IntroductionTop view of  6-inch PVC pipe gutter system attached to shed roof  catchment area & side view of  water storage container with PVC gutter and downspout. sustainability/2015/03pr2• Storage Containers: Hold the water until it is ready to be used. Make sure that your containers block out sunlight so you don’t get algae growth inside them. Most people choose to use plastic containers such as 55 gallon drums or 275 gallon IBC totes because they are easy to modify and relatively lightweight, but just about anything that can hold water will do the job. You can save money by purchasing used containers, however you need to make sure that they weren’t previously storing dangerous chemicals.• Overflow: Directs any water in excess of  what the storage containers can hold out of  the system and ideally to a place where it can be made useful. We attached a hose to our overflow so we can direct the excess water wherever we think it is needed most.• Sunken Earth Basin: Catches the overflow in a sunken basin to hold and absorb the water for a designed landscaping plant community.• Delivery System: Allows the water to flow out of  the storage containers to where it is going to be used. Typically it will consist of  a valve that is built into the bottom of  the storage containers and a hose that attaches to that valve.• Filters: Prevent the system from getting clogged with debris such as leaves, insects, and dirt. If  there are trees nearby, you will definitely want to install a filter in the gutter at the point where it flows into the downspout. This will prevent the downspout from clogging. You will also need to remove the leaves from the gutter as needed. To prevent dirt and insects from ending up in your storage containers, place a filter at the bottom of  the downspout. Chicken wire or something similar will work great to filter out leaves, and cheesecloth or any other fine material which readily allows the passage of  water but not solid objects will filter out the smaller debris.Once again, these are the basic components of  a rain harvesting system. Information regarding more complex systems can be found online.  Utah’s Rain Harvesting LawsIt is important to be aware of  Utah’s laws concerning rain water harvesting. Luckily it is pretty simple: • The maximum amount of  water storage capacity for a parcel of  land is 2500 gallons. Use of  water is limited to the same parcel of  land on which the water is collected and stored.Gutter downspout with cloth screen to catch debris before entering the water storage container.  • You need to register your system only if  one, or both, of  the following conditions apply:- You have more than two collection containers.- You have a collection container that exceeds 100 gallons.If  your system meets either of  these conditions, then you need to register it online. This free registration requires your name, address, and the total volume of  containers.General Design and Maintenance1. Determine your roof ’s surface area by multiplying it’s length by its width. Do not take into consideration the pitch or slope of  your roof  when figuring this out. In fact you do not need to get on your roof  at all, just measure the length and width of  your house standing on the ground (and it doesn’t need to be exact!).            Length (ft.) X Width (ft.) = Surface Area (square ft.)   Ex. 30ft. X 50ft. = 1500 square ft. = Roof  Surface Area2. Decide how much water storage is ideal for your needs and your roof  size. Obviously bigger roofs can collect more water than smaller roofs. But the main factor that determines how much water your system is capable of  collecting is the amount of  rainfall itself. The next formula will help you3know how much rain water (in gallons) will fall on your roof  during any given amount of  rainfall. So, if  you wish to have enough storage space to collect all the water falling on your roof  for a 1 inch rain event you will need much more storage than if  you only wish to be able to capture all of  the water from a 1/4 inch rain event. 3. Include the runoff  coefficient to the equation. A portion of  the rain water that reaches the catchment area will evaporate or be absorbed depending on the surface material. This can account for 5 to 20% of  the total volume of  rain water. To account for this we will multiply by 0.9 to get a more accurate total storage volume.Multiply the roof ’s surface area by:  • 0.062 to find out how much rain (in gallons) will fall on your roof  during a 1/10 inch rain event. • 0.157 to find out how much rain (in gallons) will fall on your roof  during a 1/4 inch rain event.  • 0.312 to find out how much rain (in gallons) will fall on your roof  during a 1/2 inch rain event. • 0.468 to find out how much rain (in gallons) will fall on your roof  during a 3/4 inch rain event. • 0.623 to find out how much rain (in gallons) will fall on your roof  during a 1 inch rain event.Surface Area (square ft.) X Conversion Factor X Runoff  Coefficient = Amount of  Rain (gallons)Ex. 1500 square ft. X 0.157 X 0.09= 211.95 gallons of  storage needed for a 1/4 inch rain eventSo, in this example, if  I want to collect and store all of  the water that falls on my roof  during a 1/4 inch rain event, I need at least 212 gallons of  storage space. Any rain that falls in excess of  a 1/4 inch will be forced to exit through the overflow as my storage will not be large enough to hold it.Keep in mind that in Ephraim as an example, a 1 inch or greater rain event occurs a little less than once per year, a ½ inch to 1 inch rain event occurs 3-4 times/year, and a 1/5 inch – ½ inch rain event occurs about 9 times/year (Source: Ted Olson). Also, from the beginning of  April to the end of  September, Ephraim ;typically receives 5.33 inches of  precipitation with the months of  April, May, and September each receiving about 1 inch of  rain while the months of  June, July, and August each receive about 7/10 of  an inch of  rain (Source: USU Climate Center).Ideas for Increasing Water Pressure in your SystemPressure is what forces water through the sprinklers or emitters in an irrigation system. Gardeners should note that their storage containers alone will not provide enough water pressure to allow them to use irrigation systems such as sprinklers or even most drip tapes. To overcome this problem, the gardener may either: 1. Use an irrigation system that can operate with extremely low water pressure,2. Modify the rain harvesting system to increase water pressure, or 3. Use a combination of  both strategies. PVC drip irrigation systems are efficient, require very little water pressure, are adjustable and inexpensive, and may be a suitable irrigation system to use with a rain harvesting system. For more information on how to build these systems check out Jeff  Banks PVC drip irrigation fact sheet (https://extension.usu.edu/files/publications/publication/Horticulture_Home_2008-02pr.pdf). Alternatively, there are two basic ways to increase water pressure in your system; you can add a water pump, or you can elevate the rain storage containers.Elevation Gain Results in Greater Water Pessure• For every foot of  elevation that the storage containers are raised, the water pressure increases by 0.43 psi. • 1 ft. of  elevation gain = 0.43 psi • 1 psi = 2.31 ft. of  elevationTips for passively increasing water pressure in your rain harvesting and irrigation systems:• Elevate storage containers.• Connect all storage containers at the bottom (as opposed to the top like we did). This will reduce the rate at which the water level goes down in the storage tank(s) thereby reducing the rate at which the water pressure decreases.• When building your irrigation system, install valves on all lateral lines so that the whole system doesn’t have to be open when watering. You can then open and close the lateral irrigation lines to achieve the desired water pressure.There are many ways to elevate your storage containers. Some people use cinderblocks, others build wooden frames, and others simply locate their storage containers at a higher point 4Utah State University is committed to providing an environment free from harassment and other forms of  illegal discrimination based on race, color, religion, sex, national origin, age (40 and older), disability, and veteran’s status. USU’s policy also prohibits discrimination on the basis of  sexual orientation in employment and academic related practices and decisions.  Utah State University employees and students cannot, because of  race, color, religion, sex, national origin, age, disability, or veteran’s status, refuse to hire; discharge; promote; demote; terminate; discriminate in compensation; or discriminate regarding terms, privileges, or conditions of  employment, against any person otherwise qualified. Employees and students also cannot discriminate in the classroom, residence halls, or in on/off  campus, USU-sponsored events and activities.  This publication is issued in furtherance of  Cooperative Extension work, acts of  May 8 and June 30, 1914, in cooperation with the U.S. Department of  Agriculture, Kenneth L. White, Vice President for Extension and Agriculture, Utah State University.of  their property like on a hill to take advantage of  the natural elevation difference on their land. If  you choose to elevate you storage tank(s) keep in mind that water is heavy, and lots of  water is very heavy. If  building a structure make sure it is strong enough to support your tank when it is completely full. You can calculate this by multiplying the number of  gallons your storage can hold by the weight of  a single gallon of  water (8.34 lbs.), and then by adding the weight of  your storage tank(s) when they are empty.Although water pumps can be expensive, they are fairly simple to install and use, and are an extremely effective way to increase water pressure.Planning and Building your Rain Harvesting SystemOnce you know how much water storage you want in your system, you are ready to buy or build your system. Every house and yard is different, and you should adapt your system to fit your location and purposes. There are many “how to” videos on the internet which describe the process of  building a rain harvesting system. Although we discussed the steps in this fact sheet, we highly recommended that you watch a couple of  these videos to get a visual idea of  what we are describing. This will also show you the variety of  ways people build their rain harvesting systems. Once again be creative and do what makes sense for your needs, your budget, and your location.You can also visit USU Extension’s Utah Water Quality Rainwater Harvesting website for more information: http://extension.usu.edu/waterquality/htm/urbanstormwater/rain-water-harvesting/Review of  Steps:1. Install gutter system. 2. Build elevation structure. 3. Modify storage container(s) so water can both flow in and out of  them, as well as between them. 4. Modify downspout. 5. Install overflow. 6. Install filters. 7. Collect rain!Useful Conversions• 1 cubic ft. = approximately 7.48 gallons• 1 inch = 1/12 of  a foot• 1 gallon = 8.34 lbs.• 1 ft. elevation gain = 0.43 psi• 2.31 ft. elevation gain = 1 psiThank you to Bob Newhall of  Western SARE for donating some of  the material used in Sanpete County’s Extension rain harvesting system.Additional ResourcesLancaster, B.  (2006). Water-harvesting calculations.  Rainwater Harvesting for Drylands and Beyond. Retrieved from: http://www.harvestingrainwater.com/rainwater-harvesting-inforesources/water-harvesting-calculations/University of  Arizona Water Wise Program. (2008). Residential Rain Water Catchment Systems.  Retrieved from: http://cals.arizona.edu/cochise/waterwise/usefulinfo.pdfUtah Division of  Water Rights.  Rain Water Harvesting Registration.  Retrieved from: http://www.waterrights.utah.gov/forms/rainwater.aspWatershed Management Group. (2012). Green Infrastructure for Southwestern Neighborhoods. Retrieved from: https://wrrc.arizona.edu/publications/water-harvesting/green-infrastructure-southwestern-neighborhoodsExample: 220 gallons (total storage capacity) X 8.34 lbs. (weight of  1 gallon of  water) = 1,835 lbs + weight of  empty storage tanks = the weight your structure needs to support

Rainwater Harvesting for the Home and Farm

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Rainwater Harvesting for the Home and Farm

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