Toilet Flushing with Harvested Rainwater in New Mexico

Using harvested rainwater for toilet flushing in New Mexico is a practical way to reduce your water bill and conserve municipal supplies. With 14.6 inches of average annual rainfall, a 1,500-square-foot asphalt shingle roof in New Mexico can collect approximately 9,047 gal per year. toilet flushing requires roughly 20 gallons per day per person, year-round. With this setup, rainwater can meet approximately 62.0% of your toilet flushing needs, saving an estimated $63.33 per year.

Annual Harvest 9,047 gal 1,500 sq ft roof
Annual Demand 14,600 gal toilet flushing (2 people)
Demand Met 62.0% of toilet flushing
Rec. Tank 1,000 gal storage capacity

Monthly Supply vs. Demand for Toilet Flushing in New Mexico

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 374 1,240 -866
February 374 1,120 -746
March 299 1,240 -941
April 299 1,200 -901
May 449 1,240 -791
June 598 1,200 -602
July 1,645 1,240 +405
August 1,794 1,240 +554
September 1,346 1,200 +146
October 897 1,240 -343
November 449 1,200 -751
December 523 1,240 -717

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 New Mexico for toilet flushing (calculated for 2 people).

Roof Area Annual Harvest Demand Met Rec. Tank Savings/Year
1,000 sq ft 6,029 gal 41.3% 55 gal $42.20
1,500 sq ft 9,047 gal 62.0% 1,000 gal $63.33
2,000 sq ft 12,060 gal 82.6% 1,500 gal $84.42
2,500 sq ft 15,076 gal 100.0% 2,500 gal $102.20

Setting Up Rainwater Harvesting for Toilet Flushing in New Mexico

Connecting rainwater to your toilets in New Mexico 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 New Mexico 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 New Mexico

Upgrading to a metal roof increases your collection efficiency from 80% (asphalt shingle) to 95%, boosting your annual harvest to 10,742 gal from a 1,500-square-foot roof. This increases your toilet flushing demand coverage to 73.6% and raises annual savings to $75.19. 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 New Mexico

Explore how harvested rainwater can serve other needs in New Mexico:

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