The distance between septic tank lids is basically different for various sizes of tanks. A 1200 gallon concrete septic tank have the lids at the distance between 6.2 to 6.7 feet, if you own 1,000 gallon septic system that distance between around 7 to 7.5 feet, and as well for 1500 gallon tank have lids between 8.5 to 9 feet and as well distance increase by increase the volume of septic tank and that provide the septic tank lid dimensions