I have water softener and Whole house filter installed in the basement. Now that I am going to finish the basement, I need to plumb a line to the fridge to replace the saddle valve. Then I think that I can get a reverse osmosis system installed the basement and plumb lines to the sink and fridge.

Is reverse osmosis system redundant since I already have a whole house filter? The filter is a Whirlpool whole house system.

  • You didn't ask, but reverse osmosis will run your water bill way up. Only about 1/5 of the water gets filtered the rest is wasted.
    – Tyson
    Commented Jul 7, 2016 at 14:39
  • The RO system will only supply water to the icemaker and drinking faucet. The water usage is not very high.
    – cuteCAT
    Commented Jul 7, 2016 at 14:47
  • 2
    Question the zeroth - what's in your water? What are the test results? Without testing, you are simply blindly applying things to your water that may or may not do any good, or be needed at all.
    – Ecnerwal
    Commented Jul 7, 2016 at 18:25

1 Answer 1


The whole house filtration system that you cite is a filter. The specs for this filter suggest that it removes chlorine and pharmaceuticals, so I think it's a carbon filter. It's possibly a good filter (there are variable levels of quality carbon filters) and it sounds like there's a timer that flushes/cleans it (that's convenient) but it is not an RO system. RO systems are very different from filters.

An RO system absorbs and removes dissolved ions (filters don't do that). Whether you need an RO system depends on what ions are dissolved in your water.

  • RO systems remove salts and other mineral things like silicates, lead, and copper (etc.).
  • General filters remove debris like grit and clumps of microorganisms.
  • Carbon filters can remove organic molecules, like pharmaceuticals, pesticides, gasoline, urea, and chloramines.

Edit- also, you mentioned that have a water softener, which replaces calcium with sodium. RO systems then remove sodium. Carbon filters don't remove sodium, nor calcium.

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