Toilet Flushing with Harvested Rainwater in Utah

Using harvested rainwater for toilet flushing in Utah is a practical way to reduce your water bill and conserve municipal supplies. With 12.2 inches of average annual rainfall, a 1,500-square-foot asphalt shingle roof in Utah can collect approximately 9,421 gal per year. toilet flushing requires roughly 20 gallons per day per person, year-round. With this setup, rainwater can meet approximately 64.5% of your toilet flushing needs, saving an estimated $37.68 per year.

Annual Harvest 9,421 gal 1,500 sq ft roof
Annual Demand 14,600 gal toilet flushing (2 people)
Demand Met 64.5% of toilet flushing
Rec. Tank 55 gal storage capacity

Monthly Supply vs. Demand for Toilet Flushing in Utah

The table below shows how your monthly rainwater harvest compares to toilet flushing demand throughout the year. Green values indicate months where your harvest exceeds demand (surplus water for tank storage), while red values show months where you will draw down your stored reserves. Toilet Flushing is a year-round use, so demand remains constant regardless of season. Tank sizing should bridge the gap during your driest months.

Month Harvest (gal) Demand (gal) Balance
January 897 1,240 -343
February 822 1,120 -298
March 1,047 1,240 -193
April 1,047 1,200 -153
May 1,047 1,240 -193
June 523 1,200 -677
July 449 1,240 -791
August 523 1,240 -717
September 673 1,200 -527
October 897 1,240 -343
November 748 1,200 -452
December 748 1,240 -492

Harvest by Roof Size for Toilet Flushing

A larger roof collection area directly increases your harvest and the percentage of toilet flushing demand you can meet with rainwater. The table below shows how different roof sizes perform in Utah for toilet flushing (calculated for 2 people).

Roof Area Annual Harvest Demand Met Rec. Tank Savings/Year
1,000 sq ft 6,280 gal 43.0% 55 gal $25.12
1,500 sq ft 9,421 gal 64.5% 55 gal $37.68
2,000 sq ft 12,561 gal 86.0% 200 gal $50.24
2,500 sq ft 15,698 gal 100.0% 1,000 gal $58.40

Setting Up Rainwater Harvesting for Toilet Flushing in Utah

Connecting rainwater to your toilets in Utah requires a dedicated non-potable plumbing line (typically purple-colored pipe to distinguish it from potable supply). This is best planned during new construction or major renovation, though retrofit kits are available. The system includes a storage tank, submersible pump, pressure tank, sediment filter, and a backup connection to municipal water with an air gap to prevent cross-contamination. Most jurisdictions in Utah require a plumbing permit for this type of installation. The payoff is substantial — toilet flushing accounts for roughly 30% of indoor water use, and switching to rainwater for this purpose provides year-round savings regardless of season. The recommended tank size for toilet flushing should bridge at least your driest month, ensuring continuous supply.

Metal Roof Upgrade: Toilet Flushing in Utah

Upgrading to a metal roof increases your collection efficiency from 80% (asphalt shingle) to 95%, boosting your annual harvest to 11,186 gal from a 1,500-square-foot roof. This increases your toilet flushing demand coverage to 76.6% and raises annual savings to $44.74. Metal roofs also last 40-70 years compared to 20-30 years for asphalt shingle, and their smooth surface sheds debris more effectively, reducing maintenance on your collection system and improving water quality.

Other Uses for Rainwater in Utah

Explore how harvested rainwater can serve other needs in Utah:

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Use our Rainwater Harvesting Calculator to enter your exact roof area, material, and combine multiple uses for a comprehensive harvest analysis. See all rainwater harvesting data for Utah or compare all 50 states.