Water Temperature: Usually, the supply line is installed on the cold water line. This is because hot water lines are above the 100 degree limit of the RO membrane. Of course, freezing temperatures will freeze the membrane and cause it to foul. If your water is cold; try to get a bucket (or something to hold water in) and some extra supply tubing (about 10-15 feet). Coil the tubing in the bucket and fill the bucket with hot water. This will gradually heat the water back up. For hot water, a chiller before the unit would be okay. You can also use the bucket trick, but fill it with cold water and/or ice. You can mix hot and cold water (especially if you have the faucet adaptor), but we recommend the bucket method more. Water Pressure : (Yes, you should get a $15 pressure gauge) If it's low (below 40 PSI), get a booster pump. They're easy to install and work great. If it's too high without a booster pump, get a pressure regulator. These are also easy to install and use. Remember; clear housings can only withstand up to 75 PSI. White housings can withstand up to 100 PSI.