Maintenance of Septic Tanks (Type 1 - No treatment Plant)

Maintenance of Septic Tanks (Type 1 - No treatment Plant)

Maintenance of Septic Tanks (Type 1 - No treatment Plant)

When contracting Western Pacific Engineering Group Limited for the design of your septic system, you will receive a maintenance manual just after the septic system construction has finalized. This manual has been specifically written to keep in good condition the septic tank that you have at home.

There are three types of treatment the sewage can receive. The decision on which one to use is based in various factors some of them being the type of wastewater and, the composition of the soil where the septic system will be built. Meaning that, not all the produced wastewater will be the same in every place and neither the land will have the same features everywhere. That’s why the design of a septic system must consider the type of use of water, the texture and structure of the soil layers and other factors as well.

Let’s keep in mind that the manuals given to our clients are specifically written for the client’s septic system based on the type of treatment the sewage is receiving.

To better understand how the system operates it is necessarily that you know the basics. We will answer some of the basic questions our clients usually have. The definitions and explanations here given are also written in our manual.

What is wastewater? Wastewater, or sewage, is generated using toilets, bathroom sinks, showers and bathtubs, kitchen sinks, garbage disposals, dishwashers and washing machines. The average person produces about 50 to 75 gallons per day of wastewater. The wastewater contains dissolved organic and inorganic materials, suspended and settleable solids, and micro organisms, including bacteria and viruses.

Basically, the capacity of your septic tank is then defined by the number of bedrooms there are in your house, the number of occupants, and the purpose of use.

Why do I need a septic system? Because A Direct discharge of wastewater to surface waters, groundwater, or ground surfaces will result in public health hazards. To protect the environment, most of the homes without sewerage utilize septic tanks to remove solids and greases, and infiltration fields, or other types of soil absorption systems, for wastewater disposal.

What is a septic system?A septic system is a configuration of different wastewater treatment methods. Depending on several variables, for instance, the amount of wastewater generated and the general ground properties, a septic system would consist either of an arrange of a septic tank or a treatment plant as a first treatment system, and an infiltration field, where the pre-treated water is infiltrated back to the ground and at the same time wastewater will receive the final treatment.

What is a septic tank?Septic tanks are watertight containers which remove large solids and greases, provide anaerobic digestion of the solids, and storage of the sludge and scum. Septic tanks are constructed of concrete, bricks, clay, or synthetic materials such as fibreglass. Baffles are placed within the tank to improve solids settling and prevent the scum layer of lightweight solids, fats and greases from floating out of the tank with the effluent.

How does a septic system work (type 1)?  Solids settle at the bottom of the tank to later be digested by bacteria which lives in environments without air (anaerobic bacteria). Some of the products of anaerobic digestion are gases, including methane, carbon dioxide, and hydrogen sulphide, which has an odour like that of rotten eggs. The gases are vented from the septic tank through the household plumbing vents.

Inorganic and non-biodegradable materials cannot be digested by the micro organisms in the septic tank and accumulate in the sludge or digested by the micro organisms in the septic tank and accumulate in the sludge or scum layers. The sludge and scum layers must be removed periodically to prevent the accumulated solids and greases from flowing into the soil absorption system and clogging the soil pores. If washing machines, dishwashers, and garbage disposals are used, the amount of sludge will increase, and the septic tank will require frequent cleaning.

Effluent from the septic tank flows by gravity to an infiltration field for disposal. The wastewater effluent is absorbed by soil particles and moves both horizontally and vertically through the soil pores where the dissolved organic material in the effluent is removed by bacteria which lives in the top ten feet of the soil.

As the effluent moves through the soil, the temperature and chemical characteristics of the wastewater change and create an unfavourable habitat for most bacteria and viruses. Therefore, as the septic tank effluent moves through the soil, organic material and micro organisms are removed. The wastewater generally percolates downward through soil and eventually enters a groundwater aquifer. A portion of the wastewater moves upwards by capillary action and is removed at the ground surface by evaporation and transpiration of plants.

To ensure that the sewage is treated adequately, in the soil, minimum separation distances have been established between infiltration fields, fractured bedrock, groundwater, streams, cut banks, wells, water supply pipelines, houses, and property lines.

When adequate soil depth is not available, untreated sewage seeps from sides of sloping cut banks, enters streams, or contaminates groundwater.

What happens when the septic systems fail? Sewage starts to collect on the ground surface or seeps from the side of a bank, or when the household plumbing becomes clogged; water and sewage from toilets, drains, and sinks are backing up into the home, bathtubs, showers, and sinks drain very slowly; gurgling sounds in the plumbing system; Standing water or damp spots near the septic tank or drain field; bad odors around the septic tank or drain field.

As the infiltration field becomes older, a bacterial slime mat grows in the soil under the trench. The mat functions as part of the wastewater treatment process; however, the mat also reduces the percolation rate. Percolation rates are also reduced by solids which flow from septic tanks that have not been pumped and by flooding due to high groundwater or sewage flowing from neighbouring infiltration fields

The sewage carries pathogens and other dangerous contaminants. Exposure to these pathogens and contaminants can make people and animals sick. When a septic system is not working properly can cause a health hazard by letting untreated sewerage reach water bodies (ground water, streams, wells, etc.) making them dangerous to use.

Now that we are aware of the dangers of a failed system, how can we avoid this from happening?

Have your septic tank pumped. If the solids in your septic tank are allowed to build up, they will eventually find their way into your septic field, clogging it with sludge.    

Do not pour harsh chemicals (like bleach) and non-biodegradable materials down the toilet or drains. Harsh chemicals can kill the bacteria you need inside your septic tank and not-biodegradable material will not break in the septic tank. However, normal household use will not harm the bacteria.

Limit your water use.Your septic system is designed for a certain number of gallons per day based on the absorptive capacity of the soil in your septic field and the number of bedrooms in the house. If your water use exceeds what your septic system is designed for, the septic system will fail. That’s why you should:

  • Repair leaking faucets.
  • Install flush toilets and water conservation aerators for faucets and showers.
  • Do not leave water running when not necessary. Shorten the time for taking showers.
  • Use dish and clothes washing machines with full loads only.
  • Space your loads of laundry. Do 1 or 2 loads per day. Not 8 loads in only one day.
  • Never connect roof drains and yard drains to septic tanks.


Reduce the use of the garbage disposal. A garbage disposal will fill your septic tank a lot faster. It’s just better to scrap your dinner plate off into the garbage.

Remove clear water sources from draining into your septic system. Water softeners, dehumidifiers, central air conditioners all have discharge lines that are often connected to the septic system. The water coming from these sources is classified as clear water and can be discharged to the surface of the ground or to a road ditch along with your footing sump water.

Leave your septic system alone. Septic fields work best when they are in well-drained, open, grassy areas that are relatively undisturbed. Disturbing the septic field area can lead to problems.

  • Do not drive over your septic field.
  • Do not put additional dirt on your septic field area.
  • Do not plant trees in or near your septic field.
  • Do not build over your septic field. This includes decks, patios, swimming pools and buried sprinkler systems.
  • Do not allow run-off water to drain over your septic field area.


In addition, users of a septic system must observe the following basic rules to ensure satisfactory operation:

  • Inspect every six months, and, if necessary, pump septic tank every one to two years.
  • Reduce the amount of water used during winter and spring when groundwater levels are high.
  • Never wash down sides of septic tank when it is pumped. The remaining slime contains bacteria which will be needed to digest the wastewater.
  • Never pour used motor oil into the septic tank.
  • Never discharge brine (salt water) waste from self-regenerating water softeners to the septic tank. The high salt concentrations will clog the soil pores.
  • Never add sodium hydroxide or potassium hydroxide to the septic tank. These chemicals will affect solids settling and cause the sludge to flow into the infiltration field.
  • Never construct infiltration field near another infiltration field. The soil will become saturated and both systems will fail.
  • Never construct infiltration fields in impervious soils, near fractured bedrock, on steep slopes, or on flood plains.
  • Never plant small or medium-sized trees within ten feet of infiltration fields or large—sized trees within 20 feet of infiltration fields. Roots will clog the pipelines.
  • Never plant vegetation which requires excessive amounts of water on top of the infiltration field.
  • Never drive vehicles or place heavy objects, such as portable swimming pools, over septic tanks and infiltration fields. In addition, stakes-for-plants and supports for children’s swings should not be placed over septic tanks and infiltration fields.
  • Never discharge water from washing machines directly to the ground surface or infiltration fields. The wash water contains chemicals and bacteria which will contaminate surface waters and cause a public health hazard. The wastewater also contains fine solids and soap scum which will clog the soil pores.

The following is a brief schedule that will help you keep track of the maintenance of your septic system.




Check for odours inside the house and on the perimeter of the septic field.

Quarterly or whenever you feel unusual odours.

Check infiltration field for swampy areas or saturation.


Solids Removal Test (septic tank) See Appendix C.

Once every sixth months.

Tank empty and de-sludge

Every one or two years, depending on solid removal test result.

Effluent sampling and testing.

As per permit stipulation or once a month for the first year.


Visit the website again and don’t forget to check the recent posts. We’ll be talking about the most common myths when it comes to septic tanks.  See you then!



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