Pressure tanks, which also act as reservoirs for the home, are used to give your water more pressure. So if you are on a well, or using a water storage tank - these tanks will allow you to get all the pressure you need to every sink, shower, laundry etc. These used pressurized air - and do not require electricity. They also save your pump from working so hard as your pump will only run when the pressure tank is empty.
These are available in three sizes: