Get our free book (in Spanish or English) on rainwater now - To Catch the Rain.
M Street Eureka rainwater catchment
Nicole Vincent designed a rainwater catchment system for the residential property located at 1402 M St in Eureka, California. The owners of the house are principals with Democracy Unlimited of Humboldt County (DUHC). DUHC is a non-profit organization that educates citizens about the illegitimate seizure of our authority to govern ourselves. They design and implement grassroots strategies that exercise democratic power over corporations and governments. DUHC seek to create a truly democratic society by provoking a non-violent popular uprising against corporate rule in Humboldt County that can serve as a model for other communities across the United States.If you would like to learn more about DUHC please check out there website at www.DUHC.org
The rainwater catchment at 1402 M St is just the beginning of their move towards sustainability. Water collected from the system drip irrigates their vegetable garden,berries, fruit trees, and landscape.
Rainwater catchment System, Rainwater Collection System, Rainwater harvesting process are words commonly used to describe the system we will design and construct. "Rainwater harvesting is the capture, diversion, and storage of rainwater for landscape irrigation and other uses." The most common type used today, is the roof catchment system. Roof catchment systems use gutters and downspouts, from which water flows by gravity into storage containers, which should be sized to collect as much rainfall as possible. An existing roof is used to capture rainwater that is gravity fed into a storage tank via gutters and down pipes(Texas A&M,2003).
There are a number of key requirements common to all effective tank designs:
- A functional and water tight design
- A solid, secure cover to keep out insects, dirt and sunshine
- A screened inlet filter
- A screened overflow pipe
- An extraction system that does not contaminate the water
- A soak away to prevent spilled water from forming puddles near the tank.
Why spend the time and money to collect rainwater when the city provides you with as much water as a person needs? Well,there is a long investment payback period of about two years for a rainwater catchment system, however, there are many immediate benefits such as the following:
- Landscaping accounts for 30 to 50 percent of a households total water use.
- Rainwater is free of salts and other minerals that can be harmful to root growth.
- It will help control erosion and flooding near the house.
- During times of drought or emergencies, a source of water will be available, when other sources are depleted or inaccessible
Insert drawing of design [image needed]
Rainwater Collection Pathway
- Rain falls onto the 541 ft2 section of roof selected for collection and down to the gutters where it then slides to each of the 4 downpipes. Halfway down it is diverted into PVC pipe that carries the water horizontally at a 2% slope into a 2500 gallon polythylene water tank. An outtake PVC pipe at the bottom of the tank extends ~20ft under the building through the crawl space and ends in the main yard. There are multiple spickets for separate drip irrigation hoses to water different sections of the yard and garden hoses.
The 104 in. by 104 in. pad gives enough space between the water tank and the house for maintenance or repair access. A perimeter of speed and corner blocks 8"x16" lined with rebar and filled with cement will create the support for the 2500 gallon water tank at 20,000 lb.
Rainwater Storage Tank
To determine the appropriate size of tank the following were considered
- How much water usage will the house use per month for their landscaping?
- What is the total area of the roof?
I measured the perimeter of the home Length*width = total area
- How much storage will they need for their rainwater supply to last throughout a dry season of 3 months?
The house has city water as a back up in case their storage of rainwater is depleted, however, 2000 gallons of stored rainwater will last them up to three months.
Annual Precipitation Table for Eureka
Rainwater tank Storage Data
To find the data below I used Mathew's calculator Tank size: 2500 US Gallons; Roof collection area: ~500 Square Feet
|Rainfall in.||Volume US gal.||% of Tank|
Available water calculation
Here is a simple worksheet to predict the amount of water available to collect:
- Multiply the catchment area by 0.550 to determine gallons per one inch of rain
- Multiply the answer to #1 by the average annual rainfall in our area
- This number is an estimate for the number of gallons available to collect in one year
Equation for Eureka, Ca
Number of gallons available to collect in one year:
The system will store rainwater in a 2500 Gal polythylene Tank that is 86" or 7ft tall and has a 96" or 7.9ft Diameter . A tank this size can easily interfere with the usable space in the main yard.
The gutters were cleaned of debris and overhanging branches before we worked on the down pipe connections.
Each downpipe has a diverter that allows the rainwater to flow to the tank or switch it when the tank is full to its original path through the existing downpipe.
All possible areas were considered for the location of the raincatchment system. The best location for the tank is outside of the main yard at the highest point of elevation. A tank this size can easily interfere with the usable space in the main yard. A list of the advantages and disadvantages of every area were key to eliminating it down to one area.
- The tank is out of the way of the owners yard space.
- The site is at the highest point on their property.
- The downpipes are close and also hidden from the view of the owners.
The Four Disadvantages of our chosen location
- The gutters are on the second story
- The ground has a moderate incline
- The tank is far from the main yard (how will they access the water?) We will send the outlet pipe under the smallest section of the house through the crawl space to the main yard.
- There are two large shedding trees that hover over the systems potential gutters. These trees will be trimmed and consistently maintained to increase efficiency of the system.
The water pressure is affected by the tanks water level. As the tank fills the water pressure increases
DUHC's raincatchment system needed to be durable yet affordable.
|Qty.||Description||Cost per item||Total Cost(incl. tax)|
|1||Norwesco 2500 gal. poly-tank||$1,093.00||$1,093.00|
|1||Baseplate Tamper 4hr Rental||$42.50||$44.29|
|1||Wheel Barrow rental||$42.03||$42.03|
|3||#4 Bar 40gr.||$5.14||$17.42|
|3||60 LB Concrete Ready Mix||$3.49||$11.00|
|3||Couple COMP SCH 40 2"||$9.99||$29.97|
|3||90 degree elbow||$2.19||$6.57|
|4||45 degree elbow||$2.69||$10.76|
|2||2"TEE SCH 40||$2.29||$4.58|
|1||PVC 2" Threaded ball valve||$11.49||$11.49|
|1||PVC 2" Union||$9.49||$9.49|
|1||PVC bushing 2x3/4||$1.59||$1.59|
|1||PVC 2" male adapter||$1.25||$1.25|
|1||SCH80 Nipple 2x3||$1.25||$1.25|
|1||Christy's Red Hot PVC cement 4||$3.49||$3.49|
|1||Teflon Tape 1/2x520 in||$2.49||$2.49|
|1||3/4 in adapter brass||$2.49||$2.49|
|1||5 faucet manifold||$8.31||$8.31|
|3||Bushing 3" to 2"||$2.29||$6.87|
|.6"||PVC 1 1/2" SCH40||$1.03||$1.03|
|6||PVC SCH40 2"x10ft||$8.99||$53.94|
|4||PVC SCH40 2"x10ft||$7.90||$31.60|
|1||25'Poly-strap pipe hangers||$3.29||$3.29|
|1||Drill Bit 1/4"||$7.49||$7.49|
|1||Stainless steel screws #8x1-1/4||$14.99||$14.99|
|3||2x3x3 PVC Offset Tile adapter||$2.93||$8.79|
|Total Cost of System||$1,629.30|
The Tank Pad
Building a sturdy and level pad for the water storage tank is very important When the water tank is at its full capacity of 2500 gallons it will weigh approximately 20,000lbs. The tank should have the weight of the water evenly distributed. Any slope can cause more weight and therefore pressure on one location of the tank.
- Ready mix Cement
- 1/2 yard Sand
- 2 yards Medium river rock
- Speed block 8"x16"
- Corner block 8"x16"
- 1/2" Rebar
Minimum Equipment Needed
- Baseplate Tamper (rented)
- Site Leveler and string level
- Wheel Barrow and 5 gallon buckets
- Building a sturdy and level pad for the water storage tank is very important.
- Concrete blocks line the perimeter of the pad with corner blocks cemented together and leveled.
- Rebar was placed along the notches of the concrete blocks
- Bailing wire is tied around each joint where two ends of rebar meet.
- Cement was mixed and poured into concrete blocks
- The cement was allowed to set for 3 days
- The pad center was filled with Medium sized rock
- We topped the pad with a sand layer
- Extension ladder
- 8ft A-frame ladder
- Tool belt
- Respirator(Heavy duty)
- All pipe is 2" Schedule 40 PVC unless noted otherwise
- 67ft PVC
- Christy's Red Hot PVC Cement
- Polyethylene pipe strap
- 2"x3" Downpipe diverters
- 2" Couple Comp
- 33 ft SCH 40 2" PVC
- PVC SCH 80 nipple
- PVC SCH 80 Thread ball
- PVC coupling
- PVC union
- 90 degree elbow
- 45 degree elbow
- 2" to 3/4" reducer
- 3/4" brass hose adapter
- 5 faucet manifold