Sorry!!! This is a repeat post. I got an error message when I posted the first time and I tried to find the post and couldn't so I reposted it. So sorry!!!

The question is what is in your water that you don't like?

Once you decide that we can advise on the correct way to deal with what you don't like.

Regardless, whether an RO will fit under your sink depends on the model RO you choose and the available space underneath the sink. An option is that ROs can be mounted in the basement if that is proximate to the sink in the kitchen or remotely up to a point.

You'll get water that has less dissolved minerals. For every one gallon of RO water produced, ~ 3 or so gallons will be discharged as waste. There are ways of dealing with(minimizing or reusing) the discharge.

It may be more practical to locate the unit elsewhere - basement, garage, ... where it is easier to replace the pre-filters and the membrane. The storage tank can also be larger and the system can be more robust than the typical under the sink RO system.

Reverse osmosis systems can be placed just about anywhere, as long as you have a feed line for the input water, and somewhere for the system to drain. And reverse osmosis will remove fluoride, along with just about everything else in the water. If you are installing the carbon filter for the whole home to help with the quality of the drinking water through the reverse osmosis system, it won't be needed. But it is nice to have better water throughout the home.

Here is a link that might be useful: Reverse Osmosis Systems

Still shilling for an RO vendor in Canada, I see. So, MichaelsAd, does the whole company condone theft, or are you the only one?