Key Takeaways:

• It's Not "Waste," It's "Discharge": The water an RO system sends to the drain is actually carrying away the contaminants it has removed. It's a necessary part of the purification process.
• Modern Systems are Efficient: While older RO systems had high discharge ratios (like 10:1), modern, high-quality systems (including USA-made options) are much better, often in the range of 2:1 to 4:1.
• The Actual Amount is Small: For a typical family, the total amount of water discharged by an RO system in a whole year is often less than what a single load of laundry uses.
• The Cost is Pennies: In DFW, the cost of the discharged water is typically only a few dollars for the entire year. The value of pure, safe drinking water far outweighs this minimal cost.

One of the most common concerns we hear about Reverse Osmosis systems (with USA-made options available) is the idea that they "waste" a lot of water. It's a valid question, but it's important to understand the process and the actual numbers involved.

Why RO Systems Discharge Water

An RO membrane works by using water pressure to separate pure water molecules from dissolved contaminants. Think of it like a microscopic screen. The pure water passes through, while the contaminants are left behind.

To keep this screen from instantly clogging with all the removed gunk (like TDS, lead, and PFAS), the system must continuously rinse the membrane's surface. This rinsing stream, which carries the concentrated contaminants away, is the "discharge" water that goes to the drain.

So, it's not "wasted" water in the sense of a leak. It's the water that is actively doing the cleaning work to allow the purification process to happen.

How Much Water is Discharged?

The ratio of discharge water to pure water depends on the system's design, your home's water pressure, and the water temperature.

• Older/Cheaper Systems: Could have ratios as high as 10:1 (10 gallons of discharge for every 1 gallon of pure water).
• Modern, Quality Systems: The professional-grade systems we install are much more efficient, with typical ratios of 2:1 to 4:1.

Let's do the math for a family that drinks 2 gallons of RO water per day, using a conservative 4:1 ratio:

• 2 gallons (pure) x 4 = 8 gallons of discharge per day
• 8 gallons/day x 365 days = 2,920 gallons per year

What Does That Actually Mean in DFW?

2,920 gallons might sound like a lot, but let's put it in perspective:

• A single load in a modern washing machine uses about 15-30 gallons.
• A 10-minute shower can use 20-25 gallons.
• Watering your lawn for 20 minutes can use over 100 gallons.

The entire annual discharge from your RO system is equivalent to about 2-3 months of running your dishwasher once a day.

The Financial Cost

In the DFW area, water rates are roughly $5.00 per 1,000 gallons.

• 2.92 (thousand gallons) x $5.00 = $14.60 per YEAR

The cost of the discharged water for an entire year is less than the cost of a few cases of bottled water. When you consider the convenience and safety of having an unlimited supply of pure water on tap, the minimal cost of the discharge water is an excellent value.

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Reviewed by Sai Akash Tumu, TCEQ Licensed Water Treatment Specialist (#WT0007448). Our approach is to educate first. For a personalized assessment, contact us for a free consultation.

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Disclaimer: This guide is for informational purposes only. Water conditions vary, and we recommend a professional on-site water test for an accurate solution. This is not medical advice. Read full disclaimer >