Pressure tanks are used to help the water pump provide a more even or constant type of pressure in your house. A larger tank means that your pump can take longer breaks between pumping cycles and thus make your pump last longer and save you money on your hydro bill.  Pressure tanks are available in many sizes and shapes. We also have fibre wound pressure tanks available that will never rust or rot.  Increasing the size of your pressure tank would be a wise investment on a standard water pumping system.  In some constant water pressure systems the pressure tank is very small; only 1 or 2 gallons; and this is because these type of pumps run at different speeds and automatically run faster or slower depending on the water demand. These systems are very efficient on hydro and provide better performance.