Laundry with Harvested Rainwater in Washington

Using harvested rainwater for laundry in Washington is a practical way to reduce your water bill and conserve municipal supplies. With 38.4 inches of average annual rainfall, a 1,500-square-foot asphalt shingle roof in Washington can collect approximately 27,511 gal per year. laundry requires roughly 15 gallons per day per person, year-round. With this setup, rainwater can meet approximately 100.0% of your laundry needs, saving an estimated $65.70 per year.

Annual Harvest 27,511 gal 1,500 sq ft roof
Annual Demand 10,950 gal laundry (2 people)
Demand Met 100.0% of laundry
Rec. Tank 5,000 gal storage capacity

Monthly Supply vs. Demand for Laundry in Washington

The table below shows how your monthly rainwater harvest compares to laundry 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. Laundry 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 4,037 930 +3,107
February 2,841 840 +2,001
March 2,691 930 +1,761
April 1,944 900 +1,044
May 1,495 930 +565
June 1,196 900 +296
July 598 930 -332
August 598 930 -332
September 1,196 900 +296
October 2,392 930 +1,462
November 4,187 900 +3,287
December 4,336 930 +3,406

Harvest by Roof Size for Laundry

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

Roof Area Annual Harvest Demand Met Rec. Tank Savings/Year
1,000 sq ft 18,341 gal 100.0% 2,500 gal $65.70
1,500 sq ft 27,511 gal 100.0% 5,000 gal $65.70
2,000 sq ft 36,682 gal 100.0% 5,000 gal $65.70
2,500 sq ft 45,855 gal 100.0% 10,000 gal $65.70

Setting Up Rainwater Harvesting for Laundry in Washington

Using rainwater for laundry in Washington offers a unique benefit: rainwater is naturally soft, meaning you can use 30-50% less detergent while achieving the same or better cleaning results. Hard municipal water requires more soap to lather effectively, and mineral deposits can make fabrics stiff and dull over time. A rainwater-fed laundry system requires the same setup as toilet flushing — dedicated non-potable plumbing, a pump-and-pressure system, and sediment plus carbon filtration to remove any debris or tannins that could discolor fabrics. The filtration requirements are slightly higher than for toilet use because you want to protect both your clothing and your washing machine from fine sediment. A first-flush diverter on your collection system is especially important for laundry use to keep water clean.

Metal Roof Upgrade: Laundry in Washington

Upgrading to a metal roof increases your collection efficiency from 80% (asphalt shingle) to 95%, boosting your annual harvest to 32,670 gal from a 1,500-square-foot roof. This increases your laundry demand coverage to 100.0% and raises annual savings to $65.70. 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 Washington

Explore how harvested rainwater can serve other needs in Washington:

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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 Washington or compare all 50 states.