How long before a new whirlpool reverse osmosis fills the tank and stops draining? I installed the brand new system this afternoon and after 4 hours it is still draining. Does that mean the tank is still filling or is there a problem? Model is WHAROS5

  • Depends on the model and how much it uses to process, as well as tank size, and water pressure.
    – Jeff Cates
    Feb 25, 2018 at 3:28
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    Be aware that RO systems drain more water than what gets captured as the filtered water. If you are using the filtered water regularly then there will be draining regularly as well.
    – Michael Karas
    Feb 25, 2018 at 12:37
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    From this site allianceforwaterefficiency.org/… there is this quote: "Depending on the model, most RO filter systems will discharge 4 to 20 gallons (15.1 L to 75.7 L) of backwash water for every gallon of filtered water it produces."
    – Michael Karas
    Feb 25, 2018 at 12:42

1 Answer 1


That model can produce 18.4 gallons of purified water per 24hrs or about 1.3 hours per gallon. So in seven hours, a 5 gallon tank should be filled. There may be other factors that affect this. If it is still running after 10 hours, you've certainly got a problem. Note that every time you use the filtered water, there will be additional draining.

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