Rainwater Harvesting Systems, Inc.

I live in Fort Worth, Texas and I am thinking of installing a rainwater system. My roof area is about 1,450 square feet. I would like to use the water for my indoor needs and possibly irrigation.

I plan to landscape the back yard, which is the hillside, put a vegetable and herb garden on the side yard, and plant two fruit trees and blackberry bushes along one side, so I will have some irrigation needs (just not the whole yard).

The water demand of our household was 15,000 gallons at the high point of the summer to 3,000 gallons last month (December). I do not have a full year of experience in the US, but here is what I have:

Water usage in gallons:
May - 15k
June - 14k
July - 15k
August - 14k
September - 14k
October - 6k
November - 3k
December - 3k

What size of system would you recommend?

Thank you for the information. Here is a break-down of the type of rainwater system you would need to maximize your return from rainwater harvesting.

Your roof area (1,450 sq. ft.) will yield about 900 gallons of water per inch of rainfall. The average rainfall in Fort Worth is about 35 inches per year. So, during the average year (precipitation-wise), you can collect about 31,500 gallons of water. Based on your water demand, you can just about meet all of your indoor needs (@ 3,000 gallons per month) with rainwater. The irrigation demand (@ 12,000 gallons per month during the summer) exceeds the amount of water you can collect from your roof area.

My recommendation would be to use rainwater for indoor needs plus hand watering of your garden and to use municipal water for outdoor irrigation. For potable water, you will need an advanced filtration system that uses multiple filters plus UV light.

To determine the tank size, we recommend that you have enough water in storage to outlast a normal drought period. In North Texas, droughts commonly last up to 10 weeks during the summer. If your indoor demand is 3k gallons per month, it would be prudent to have 7,500-10,000 gallons of storage.

Now having figured that out, I'm sure there are also budget limitations and space requirements to consider. Often, the size of the tank accounts for 50% of the total cost of a rainwater project. If you need to cut back on costs, consider using a smaller tank and using municipal water as a back-up supply. In the future, it is quite simple to add more storage if needed.

Finally, by taking advantage of the many water-saving technologies that are available for your indoor water fixtures such as low-flow toilets and shower heads, front-loading washing machines, and water-efficient dish washers, you can reduce your demand by up to 50%. Now we're talking!