Choose the Right Rainwater Storage Tank

So you’re ready to begin harvesting  rainwater, but after just a few minutes online , you’ve realized  that size options for rainwater storage containers ranges  from as little as 55 gallons to 3,000 gallons or more. How do you know what size is best for you?

First consider these factors:

-How much rainfall do you get in your area? If you live somewhere with frequent, year round rainfall like Seattle or Portland, you won’t need as much rain storage capacity as someone in Phoenix. Here in the Charlotte area, stored rainwater will be most useful during dry spells during late spring to early fall.

-How large is the catchment surface (i.e roof area). If you have a 5,000 square foot house, there will be thousands of gallons to harvest over the course of a year, and a series of 1000 gallon tanks can hold some of it for drier times.  While an 8’x12’ storage shed or greenhouse can still harvest a useful amount of rainwater, something in the 150 to 250 gallon range would be more appropriate for a structure that size.

-What do you intend to use the rainwater for, and how much do you intend to use? If your intent is to irrigate a landscaped half acre property during a one month summer dry spell, or wash your sizable classic car collection, you’d better plan on having some serious rain storage capacity. If the goal is simply to water growing containers on your condo’s terrace, a smaller rain storage tank will do the job.

- Where will the rainwater storage tank be located, and how much space do you have there? Above ground rain tanks are typically placed within 3’ of a downspout, and can get rather bulky as they increase in capacity. Is there room for the tank, and/or room to move around it? How much site prep will be involved in creating a level placed for a tank or series of tanks to sit? If you plan to put your rain storage tank on a rooftop, can the roof safely support the weight of hundreds or even thousands of pounds of rainwater concentrated in one place?

Or try using the formulas below to calculate how much rain water you’ll need:

roof area   X  annual rainfall = maximum available for capture

Then determine….

Most days without rain  X  average daily water use = storage volume required on day one of a dry spell

If, for example, the longest stretch of days without rain was 30 days, and the average daily usage was 40 gallons, then the  volume on hand on day one of a 30 day dry spell would have to be 1200 gallons

Curious how much rainwater can your home, greenhouse, shed, garage, chicken coop, or other structure harvest ? click here to find out.