It will come with a hose thread adapter which screws on a hose bib. Depending on how you want to install it you may need to buy something to adapt it to. Many of us buy a brass garden hose wye in the garden dept at any hardware store or Walmart and hook it to the cold water supply to your washing machine, one side feeds the washer and the other the RO. Get the wye with the individual ball valves so you can shut it off, about $8 at most. Another option is called a feed water adapter which is popular with users who rent and don't want to permanently alter the plumbing. It installs on the kitchen or bathroom faucet cold water supply wall valve and can be removed with no evidence it was ever there. This is a good option as it does not tie your faucet up for hours while you make water. The last option is the faucet adapter which screws on in place of the screen on most faucets. The disadvantage is the faucet is tied up as long as you are making water and you snap it off when not making water. I prefer the washing machine hook up myself if you have one available as it gives you a cold water source and drain in an easy spot to get to and can be mounted on the wall if you have room so doesn't have to be put away after each use. The only other thing I suggest is an ATC temperature compensated handheld TDS meter such as the HM Digital TDS-3, TDS-4TM or AP-1, all less than $30 most places. Much more useful, accurate and versatile than inlines which are not temperature compensated and cannot be calibrated plus limit you to one, two or three test points which is limiting when you want to test your ATO or some bottled water or if you have the dual inline and want to test the tap water which is very important to do.