The 3-way faucet is connected to the cold (1st supply) and hot (2nd supply) water that comes either directly from the water supply or from our tank and to the clean water (3rd supply) that comes from the filtration system that has been installed!
This way we save space in our sink since we don't need to install a separate tap for the filtered water and we improve the aesthetics of our kitchen!
It's important to make sure that the faucet you choose has a different spout where the filtered water comes out of, like the faucet in the photo so that no impurities are left inside the faucet and then come out in the water you drink!