How Often Should I Pump Out My Tank?
Most individuals believe that as long as you don't have any "problems" you won't have to pump it out.
The question I always ask in response is, "What is your definition of a problem?"
If your definition of a problem is that "the toilet backs up", then you are assuming that that is the only problem to worry about.
A septic tank is designed to catch as many solids as possible so they do not go out into the treatment/disposal bed causing a blockage. The septic tank is able to seperate the solids from the liquid when the total amount of solids are less then 33% of total capacity. As soon as the total solids exceed that amount the efficiency is decreased and more and more solids exit the tank and plug the treatment/disposal bed.
The septic tank does not automatically stop accepting sewage and cause a blockage at the toilet once it reaches that 33% capacity. The tank continues to accept sewage and the total solids amount eventually gets to 100% of capacity which is what causes the blockage into the indoor plumbing. By this time thougha significant amount of solids have also exited the tank and drastically reduced the efficiency.
It is not only suggested, but mandated by the Ontario Building Code to have the tank pumped out before the total amount of solids exceed the 33% of total capacity. For example, if your tank is 4' deep, and there are 6" of solids on top and 10" of solids on the bottom, it is nearing the 33% of capacity (16' divided by 48"x100 = 33%) and needs to be pumped out as soon as possible.
The average 1000 gallon tank with 4 residents using the house will reach the 33% within 2-3 years.