DUHC Raincatchment System night.jpg
FA info icon.svg Angle down icon.svg Project data
Authors Nicole Vincent
Location Eureka, California
Status Deployed
Completed 2007
Cost USD 1,629.30
Instance of Rainwater catchment
OKH Manifest Download

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.

Literature Review[edit | edit source]

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).

Key requirements[edit | edit source]

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:

Immediate Benefits[edit | edit source]

  • 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

(Texas A&M,2003).

System Design[edit | edit source]

Rainwater Collection Pathway[edit | edit source]

  1. 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.

Foundation/Crash Pad[edit | edit source]

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[edit | edit source]

To determine the appropriate size of tank the following were considered

  • How much water usage will the house use per month for their landscaping?
  1. 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.

System Calculations[edit | edit source]

Annual Precipitation Table for Eureka[edit | edit source]

Rainwater tank Storage Data[edit | edit source]

To find the data below I used Mathew's calculator (link no longer exists, see Basic rainwater collection calculations instead) - Tank size: 2500 US Gallons; Roof collection area: ~500 Square Feet

Rainfall in. Volume US gal. % of Tank
0.05 16 0.62
0.1 31 1.25
0.15 47 1.87
0.2 62 2.49
0.25 78 3.12
0.3 93 3.74
0.35 109 4.36
0.4 125 4.99
0.45 140 5.61
0.5 156 6.23
0.55 171 6.86
0.6 187 7.48
0.65 203 8.1
0.7 218 8.73
0.75 234 9.35
0.8 249 9.97
0.85 265 10.6
0.9 280 11.22
0.95 296 11.84
1 312 12.47

Available water calculation[edit | edit source]

Here is a simple worksheet to predict the amount of water available to collect:

  1. Multiply the catchment area by 0.550 to determine gallons per one inch of rain
  2. Multiply the answer to #1 by the average annual rainfall in our area
  3. This number is an estimate for the number of gallons available to collect in one year

Equation for Eureka, Ca[edit | edit source]

Number of gallons available to collect in one year:

Equation[edit | edit source]

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.

Gutters[edit | edit source]

The gutters were cleaned of debris and overhanging branches before we worked on the down pipe connections.

Downpipes[edit | edit source]

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.

Location[edit | edit source]

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.

Advantages[edit | edit source]

  • 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[edit | edit source]

  • 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.

Flow[edit | edit source]

The water pressure is affected by the tanks water level. As the tank fills the water pressure increases

Materials/Cost[edit | edit source]

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 Tank Delivery $25.00 $25.00
26 Speed Block $2.29 $62.54
4 Closures $2.46 $11.84
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
4 Bar Bends $1.25 $5.00
3 60 LB Concrete Ready Mix $3.49 $11.00
0.5 Yard Sand $53.30/yd $28.65
2 Adapter 1.5SL1.5MPT $1.19 $2.38
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
2 Coupling $1.59 $3.18
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 Ace hacksaw $4.99 $4.99
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 Diverters $18.75 $56.25
3 2x3x3 PVC Offset Tile adapter $2.93 $8.79
Total Cost of System $1,629.30

Construction[edit | edit source]

The Tank Pad[edit | edit source]

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.

Materials[edit | edit source]

  • 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[edit | edit source]

  • Baseplate Tamper (rented)
  • Site Leveler and string level
  • Wheel Barrow and 5 gallon buckets
  • Shovels

Pad Construction[edit | edit source]

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 sit for 3 days
  • The padded center was filled with Medium-sized rock
  • We topped the pad with a sand layer

The Intake[edit | edit source]

  • Equipment
  • Extension ladder
  • 8ft A-frame ladder
  • Tool belt
  • Drill
  • Hacksaw

Safety[edit | edit source]

  • Glasses
  • Respirator(Heavy duty)
  • Gloves

Materials[edit | edit source]

  • 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

Intake Construction[edit | edit source]

The Outtake[edit | edit source]

Materials[edit | edit source]

  • 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

Outtake Construction[edit | edit source]

FA info icon.svg Angle down icon.svg Page data
Keywords rainwater catchment, rainwater, tank, valve
SDG SDG06 Clean water and sanitation, SDG11 Sustainable cities and communities
Authors zirky nics, Lonny Grafman
License CC-BY-SA-3.0
Organizations Cal Poly Humboldt, Engr305 Appropriate Technology
Language English (en)
Related 1 subpages, 8 pages link here
Aliases DUHC Rainwater Catchment
Impact 940 page views
Created April 12, 2007 by Anonymous1
Modified February 28, 2024 by Felipe Schenone
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