Common Drainfield Problems

There are many signs of drainfield failure, but a homeowner may not recognize them and simply think their tank needs to be pumped. “Wet spots and smells coming from the drainfield area are early signs of failure,” says Jerard Nighorn, vice president of Lenzyme/Trap-Cleer. “Of course backups within the home plumbing system are another sign of failure. These are signs that home owners can observe.”

Professionals can not only observe this, but also other symptoms when opening the system. “On a gravity fed system, if the tank is completely full upon opening the lid this is an early sign of back pressure from the field,” adds Nighorn. “If the wastewater in the tank is full of very black wastewater, then it is a sign of failure beginning from a bio-mat. Professionals should inspect the drainfield when cleaning the septic tank. They are the best person to read the early signs of failure and caution the homeowner about possible future failure of their system.”
According to Nighorn, septic fields typically fail because of a bio-mat buildup or imbalance, grease capping, sodium binding, roots and mechanical failure.


“A traditional septic drainfield has two types of bacteria present: aerobic which uses oxygen and anaerobic which doesn’t use oxygen,” says Nighorn. “When wastewater flows into the soil absorption area, a biologically active film develops. This slime layer, commonly called the biofilm or bio-mat, is composed of bacteria and their waste products. This slime is a chemical compound secreted by the bacteria to anchor themselves to the bottom and sidewalls of the drainage piping, the aggregate in the absorption bed, the soil interface and to each other to prevent being washed away by the wastewater flowing through the septic system. The bacteria serve a vital purpose by absorbing the organic waste, removing pathogens and breaking it down into soluble byproducts. Without these beneficial bacteria the septic system would not work. The water coming from the septic tank has already been depleted of oxygen and is thus an anaerobic environment. It is oxygen from the soil that allows the activity of the aerobic bacteria within the bio-mat.

“This aerobic activity is important to the digestion of waste from the septic tank. Aerobic bacteria use oxygen as their energy source and will digest waste faster and more efficiently than anaerobic bacteria. The anaerobic bacteria use the sulfur from the waste as their source of energy, their byproducts include a form of sulfur called sulfides, which has a rotten-egg smell. Sulfides also have a characteristic in which they react with metals, mostly iron in soil and water, to form a black, very insoluble and very sticky material which is not good for the septic system. In the presence of oxygen, sulfides slowly react with oxygen to form harmless soluble sulfates which wash down into the soil.

“Therefore, a properly functioning drainfield will have a balance of both aerobic and anaerobic conditions present. If oxygen is depleted in the drainfield, the anaerobic bacteria take over and build a strong hold. This creates a situation in the drainfield where a black slime will grow. The buildup of the black material (iron sulfide) is the number one source of a slow draining system. The more the buildup, the slower the water transferring through it. If left unchecked, it will build up to a point where the drainfield will not accept any more wastewater and the soil absorption area will fail. This causes major problems for the owner such as messy and smelly backups.

“Bio-mat problems are caused by not cleaning septic tanks on a regular basis, or overloading the designed system. When septic tanks are not maintained properly, solids leave the septic tank and flow out to the drainfield. This increases the biological demands and the bio-mat thickens to a point where the drainfield cannot handle the effluent discharge of the septic tank. In severe cases, the entire drainfield becomes anaerobic and effluent leaches to the surface. When overloaded by solids that are not properly pretreated by the septic tank, the system becomes waterlogged and the drainfield slows or fails. The same thing can happen when a system designed for a household of three is now occupied by a family of five living in the home. The drainfield gets overloaded by the amount of wastewater and slows down or fails completely.


Grease capping is another common problem in drainfields. Nighorn advises once grease capping has occurred it’s harder to fix the drainfield. You never know where the hot grease will cool into a solid–it may coat the drain line, the septic tank or the drainfield. “If it makes it way to the drainfield, it caps the bio-mat and soil area slowing the oxygen intake of the drainfield,” says Nighorn. “This thick grease cap allows very little water to penetrate and therefore does not allow for proper treatment of the wastewater. The drainfield quickly becomes flooded and slows or fails.”


“Though not a major problem in most soils, sodium binding is a common problem in heavy clay soils,” says Nighorn. “In short, clay soils are not great soils for septic systems. Over time, sodium binding becomes a problem by slowing down the drainage in the drainfield. The clay acts like a magnet and the sodium will form a crystallization that will not allow the wastewater to flow past. There are specific products which will alleviate the problem and allow the sodium to wash through the soil.”


Septic drainfields have the perfect growing conditions for roots–plenty of water and nutrients which help the roots grow so big they cause blockages in the drainfield. “Effluent capacity is reduced by the roots and the system does not work properly,” says Nighorn. “In most cases, roots can be mechanically removed and then treated with a good high-quality root control product. However, they will come back so on-going maintenance is necessary.”


“When it comes to fixing drainfield problems, certain equipment and supplies will make your rejuvenation work more successful,” says Nighorn. “A jetter is a great piece of equipment for the beginning process, which includes cleaning the inside of the drainfield piping components. Cleaning off the solids buildup, the grease buildup and even the bio-mat buildup within the field piping is one of the first steps in drainfield restoration services.”

“The jetter can also be used for cutting roots. This provides a quick result and most times the system will start to accept effluent immediately, but be cautioned that this is just a temporary solution. You have just cleaned the inside surface of the piping and the real problem exists in the soil absorption area which the jetter did not touch. In addition to this jetting procedure, a biological or chemical treatment should be made to attack the problems within the drainfield soil areas. The biological treatment takes a longer time, but will be the main solution to the problem.

“As for rejuvenating drainfields there are several methods,” says Nighorn. “Each of these should be presented to the customer so they can make a sound decision.

“One method is using a septic kit that includes an oxidizer along with a high-quality bacteria follow up. This attacks the bio-mat and has a mild chemical reaction in which it cleans off the bio-mat layer and creates oxygen for the bacteria to thrive. This cleansing of the bio-mat layer brings the system back into a healthy balance. This is also the most economical method of treatment and the least invasive for landscaped yards.

“Another method is installing an aerobic unit into the septic tank along with a high-quality bacteria,” adds Nighorn. “This adds oxygen to the tank and helps the bacteria thrive.”

“The third method is using equipment for ground fracturing,” says Nighorn. “This blasts holes into your septic field and allows oxygen to get to the bacteria. It is best to check with your local municipality before doing this, because it may require special licensing.”

“The last method is to install a new field or add to the existing field,” says Nighorn. “The two major aspects to consider with this method are economic budgets and disruption of the landscaping.”

“Lastly, for sodium binding and further control of roots, chemical treatments are your best option,” says Nighorn. “A high-quality manufacturer of biological products should be able to supply you with these products.
When homeowners need a fast solution to fit their budget, septic professionals should be knowledgeable of the solutions and ready lend advice on the best way to go.

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