How many times have you responded to a routine septic tank maintenance call only to find a problem that requires a significant repair or tank replacement? How do you as a service provider approach this situation with the homeowner? The homeowner first needs to be convinced further action must be taken; and once you get that far it is all about fixing the problem at the least cost, time and effort.

We are interested in hearing about some of your experiences in cases like these.

We’ll share a few of our thoughts on repairing or replacing septic tank components. Some of these we feel are common-sense solutions while others are in a gray area with probably no right answer.

ACCESS ISSUES

As you excavate a concrete tank and remove the lid, concrete falls off the bottom of the lid into the tank and exposes the rusting rebar. At the very least, the lid needs to be replaced with one that is structurally sound. Similarly, if the manhole lid is cracked or splits into two pieces during removal to pump the tank, it should be replaced and not just set back into place and covered up when the pumping is finished. This would be a good time to talk with the homeowner about a system upgrade in terms of risers to the surface if they are not already present.

After pumping and upon inspection of the tank, check for cracks, deteriorating concrete and rebar in the tank itself. If these conditions are evident on the inside of the tank, it probably needs to be replaced. The exposed rebar would indicate the tank is not structurally sound. If you find hairline cracks but no evidence of root penetration or deterioration of the concrete around the cracks, concrete repair products can be used to fill the cracks. Whether this is your approach depends on the cost of taking the cover off the entire tank and executing the repairs compared to the cost of installing a new, up-to-date tank.

It is important to highlight for the homeowner that the tank needs to be watertight to function properly, and it will not do so if the tank has cracks. Of course, there is also the possibility the tank will collapse, causing a safety hazard as well as probably coming at the worst possible time, such as a family reunion.

DEFORMATION

For polyethylene or fiberglass tanks, any deformation or loss of shape indicates structural instability and necessary replacement. You’ll identify this problem when removing the lid and finding the area around the manhole is not in the proper shape or the tank sidewalls are bowed in. Part of what makes these tanks structurally sound is their designed shape. If they are not holding that shape, it is time for replacement. The deformed tank is probably not watertight, the baffles are probably not in the right position and there is risk of collapse. No one wants to go by falling into a septic tank!

The “when to repair or replace” question becomes a little tougher when the only issue is deterioration or loss of either the inlet or outlet baffle. To answer the question, we need to consider the purpose of the baffles in the tank. The inlet baffle is critical for proper tank operation by directing incoming wastewater flow downward to the level of the clear zone. This dissipates the energy on the incoming flow, preventing turbulence that could put the settled solids back into suspension. It also ensures the wastewater has to flow in a circuitous path through the tank, allowing time for solids to settle. For that reason the inlet baffle should extend to a depth of at least 6 inches below the liquid surface in the tank but not more than 20 percent of the operating depth.

Outlet baffles must keep the floating solids or scum in the tank, preventing them from flowing directly to the next component in the system. Effluent screens are required in most places to trap larger solids in the tank. The outlet baffle also needs to extend down into the clear zone so outgoing effluent is drawn from the clear zone. This is generally thought to be a distance of 40 percent of the operating depth.

BAFFLES BY THE NUMBERS

Both the inlet and outlet baffles must extend upward at least 6 inches and no closer than to within an inch of the tank lid. This keeps the scum in the tank and from clogging the inlet while allowing room for exchange and venting of gases.

Any problem with the baffles that interferes with these functions is cause for its repair or replacement. In older concrete tanks, this may be a difficult task, while at the same time keeping the tank watertight. If the tank is not watertight, it needs to be replaced. Simply replacing the baffles is not good enough.