Make a plan

STEP 1: Tank size and dimensions

Decide on the tank size that you want based on space, budget, and water demand. We recommend the Norwesco brand from Scotts Valley Sprinkler. You can find prices and dimensions here. Overall, we recommend a tank size between 200 and 600 gallons. Consider how the width and height of your rain tank fit into your available space. Shorter, wider tanks are less prone to the effects of earthquakes. However, taller systems will have more pressure from gravity.

STEP 2: Site Assessment

Where will you put the rain tank? This will largely be determined by 4 major factors.

Factor One: Roof, gutter, and downspout availability

• Find a good downspout that you can divert rainwater from.

Factor Two: Available space

• Make sure there is space below for the rain tank. You don't have to put your tank directly under your downspout location since this is where the first flush diverter will go but it is more efficient, simple, and cheap to keep the tank nearby so you don't have to buy too much PVC and support.

• There should be enough of a height difference from the bottom of your gutter (long downspouts can easily be removed) and the top of your tank to fit a leaf catcher and still have a downward slope in order for water to flow. We recommend at least 2 feet of space.

• There should be room to access the maintenance pieces of the rain tank such as the tank itself, the leaf catcher, and the first flush diverter.

Factor Three: Slope of your site

• Find a downspout location that is uphill from where you want any excess (overflow) rainfall to be directed.

• If you intend to set up a drip irrigation driven by gravity, make sure to put your rain tank uphill from your intended garden beds.

Factor Four: Safety

• The ground should be flat and level or able to be made flat and level for the rain tank to sit on.

• The ground where you plan to put your tank (for tanks over 200 gallons) should be highly compacted. Flat land is ideal but if this isn't available, a compacted base rock or cement foundation is recommended for the tank to sit on. This will protect the rain tank from tipping or moving during an earthquake.

• Avoid choosing a spot blocking any important features like exits, electrical boxes, or windows.

• Shaded areas are ideal to protect water quality in the tank. We also recommend a tank that is black or dark colored since dark colors absorb more sunlight. This helps to limit the growth of algae within the tank by preventing excessive light penetration, thus maintaining better water quality

STEP 3: Measure 

Measure out your space. You may find it helpful to draw your site from multiple angles and to measure how much room you will have between the gutter and the top of the rain tank. 

Measure the distance from the gutter to the inlet to your tank and keep track of any 90º turns. Your tank does not need to be directly under your downspout but should be nearby. 

Determine the diameter of your PVC piping. We recommend no smaller than 3 inches.