Is Your Filter Wasting 4x the Water You’re Drinking?

Reverse osmosis water filters are water hogs. Period.

I’m talking about those easy, discreet, under-the-counter filters so many of us love, the ones that give us endless gallons of delicious, purified water. You’re feeling thirsty just thinking about it, aren’t you? Grab a glass and we’ll regroup.

If you have a reverse osmosis (RO) filter, you just used four glasses of water to make that one in your hand.

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Take a minute for that to sink in — to percolate, if you will. For every gallon of purified water a reverse osmosis filter produces, the system will work for an hour to refill each gallon you drew out, and that refill will take longer and produce more waste if you have low pressure or the water is very cold. An RO filter will use 3–5 gallons of water to process the water for a pot of coffee.

How can this be? First, a quick primer on RO filters. Reverse osmosis works to remove contaminants by using pressure to push water through a semi-permeable membrane. The filtered water coming through the membrane goes to the tap for drinking; the water too saturated with particles to make it through the membrane is diverted into waste, even though it is far from being true wastewater. If your filters get clogged over time, your system could be working for 3–4 hours for that gallon of filtered water.

That post-use water flow is what caught the eye of one of our first Buoy users. She had been using a well-maintained RO filter for years, but after attaching a Buoy to her water main, she saw water was continuing flow well after she filled her coffee pot each morning. The Buoy app alerted her to check out this potential leak, which she categorized as typical sink usage. The alerts stopped, but she noticed that the Buoy app showed a volume of water flowing that was many times larger than what she’d used for coffee. The undersink tank was refilling slowly through the RO filter, throwing away 3.5–5 gallons for every gallon of filtered water. Since her tap water didn’t need a heavy filter to improve quality, she switched to an inline charcoal filter with less water waste and cheaper filters.

So, what can you do? Are RO filters evil? Not necessarily. For some people, especially those with a less adequate water supply, they are a great way to produce filtered, drinkable water. If that’s you, here are some things to keep in mind:

  1. Maintain your system. Change your filter and prefilter regularly, because the harder a system has to work, the more water it wastes.
  2. Check your water pressure. Less pressure means the system works longer to push water through the membrane, and that means more waste. If you have low water pressure, consider getting an additional pump.
  3. Use filtered water sparingly. This might seem like a no-brainer, but knowing that it takes four gallons to make that pot of coffee means you won’t use filtered and unfiltered water interchangeably.
  4. Check your settings, and re-think your maintenance cycle. I know I just told you to maintain your system, but there’s a wrinkle: When your RO filter is hooked up to your home’s water softener.

For example, the Buoy app messaged an owner about a potential leak, and in the few minutes it took to get home, more than 100 gallons of water had been flowing. Thankfully, it wasn’t a leak, but rather the water softener’s pre-programmed regeneration cycle. It had run twice per month since she bought the water softener, but she only saw the amount of water waste when she hooked up her Buoy. She now runs the regeneration cycle once every other month and hasn’t noticed a difference in water quality — and is happy to see Buoy’s new remote shutoff feature, which lets her turn off the water to her house via the Buoy app on her phone and prevent damage in an emergency.

Water filters are necessary for some homeowners, optional for others, and unnecessary for those with a reliable, safe, tasty water supply. There are many to choose from, so weigh the pros and cons before you settle on one. Some filter systems recycle water waste toward unfiltered taps, which increases the minerals in those taps. A more involved system can send the water waste outside for irrigation, but that has its own issues (complexity, increased density of minerals, etc.), and the simplest systems are filters within pitchers. The one that’s best for you might come with some serious water waste, and that’s important information to have. Buoy can help you see how you use your water, and help you use it better.

Now, go refill your water glass.