Rain Tanks

Rain Tanks allow for rainwater to be gathered and stored for later irrigation. A single inch of rain on a 1500 square foot roof can generate 1000 gallons of runoff. Installing a rain tank is a great way to reduce your water usage and make your landscape more resilient in times of drought. 


Rain tanks range in size from small 25 gallon barrels to huge 5000 gallon tanks. The perfect rain storage option depends on your roof size, irrigation needs, and space restraints. For smaller projects, utilizing multiple small rain barrels can work well. For significant irrigation needs, installing a single large tank is often most efficient. 

Rain barrels can be linked together for additional storage.

Smaller Systems

Installing rain barrels at home is an easy way to store excess runoff. Equipping roof downspouts with a "first flush" diverter helps reduce the risk of polluted water being stored in a rain barrel. Strategically place barrels above any irrigation areas to prevent the need for pumping any water. 

5000 gallon rain tanks can stores months of rainfall for later use.

larger systems

Installing a 5000 gallon rain tank is a significant undertaking, but dramatically increases your rain storage potential. A county permit is required for installing a rain tank over 5000 gallons, but "daisy chaining" multiple 5000 gallons together does not require a permit.  


  • Must be opaque. Stored water needs to be protected from the sun to prevent algae growth

  • Lighter color keeps water cooler

  • Potable plastic is needed if using water for drinking

  • Non-galvanized if used for irrigation (or use liner)

  • Underground tanks should have swivel unions and flexible line

  • Covered, but accessible

  • Seismic requirements for larger tanks, especially vertical

Tank Site Considerations

Here are a few considerations to take into account when deciding where to place your rain tank:

  • Gravity: If you want gravity flow from your tank, you will need to find the highest possible elevation location for your tank.

  • Electrical: If you are going to pump your water, try to place tank near an electrical source and leave room for filtration piping.

  • Infiltration: your overflow water will need somewhere to go. Ideally, your surrounding soils can accept the water.

  • Aesthetics: tanks are a beautiful thing but they can obstruct a view.

  • Slope: Remember a full tank is a heavy tank, if placed on too steep of a slope, you run a greater risk of your tank tipping.

  • Heat: Choose a spot that is shaded and protected from anything that might damage the pipes (children, cows,horses etc….)

  • Distance: The closer you place a take to rain gutters the less money and materials you'll need to get it piped.

  • Design Your Overflow! think about where your water is going and install an appropriate measure - Rain garden, swales…etc.

  • Do not place tank on top of utility lines (call before you dig)

Best Rain Tank Uses 

  • Outdoor irrigation

  • Toilet Flushing: with proper treatment and disinfection rainwater can used for flushing

  • Laundry Usage

  • Water Gardening or Water Feature make-up water

  • Car Washing

  • Fire Protection

  • Other Domestic Non-Potable uses

  • Long Term Storage

  • Resilience: stored water can be a great resource in times of natural disaster or serious need

Questions? Contact the Tuolumne County RCD at (209) 984-0500 or lindsay@tcrcd.org