Tank corrosion
A common problem identified by service providers is excessive corrosion in concrete tanks around the outlet baffle. The likely culprit, hydrogen sulfide, collecting at the outlet point of the tank — the gas is heavier than air.
This problem is almost always related to the lack of proper venting through the tank — an installation error. The supply pipe from the house to the septic tank can be angled into the tank because of improper bedding of the pipe or improper backfilling that leaves the pipe suspended over an open area of the tank excavation.
In any case, either immediately or over time, the pipe enters the tank at an angle and does not allow the air to escape out of the tank and vent through the roof stack. It is very important that the tank be installed level and that the pipes into and out of the tank be properly bedded and firmly supported.
This kind of installation error can cause other problems as well. In cold climates, it can allow sewage to freeze in the pipe, ultimately causing the pipe to plug and freeze shut. If the seal where the pipe enters or exits the tank is damaged it provides a ready pathway for roots to enter the pipe and the tank, and that will cause all kinds of backup and plugging issues. The solution is to replace and level the pipes, seal the joints, and properly backfill around the tank and pipes.
Another issue that can cause blockages occurs when the inlet pipe is pushed too close to the inside baffle wall. When this happens, there is not enough clearance to allow sewage solids, such as toilet paper, to pass freely into the tank. They begin to hang up between the pipe and the wall, eventually causing a blockage that can cause a backup into the house. Here again the fix is to dig up and reposition the pipe.
