About Septic Tanks

Why Have a Septic Tank?

Septic systems provide basic sanitation for rural homes by recycling wastewater back into the natural environment. Septic tanks do not treat wastewater, they simply separate solids from liquids. The liquids drain off to a soakaway drainfield and the solids are emptied from the septic tank by tanker once a year. Sapphire provide a septic tank emptying service nationwide.

How Does a Septic System Work?

In typical septic tanks systems, all wastewater enters the system.
Septic systems all have two basic components: the septic tank itself, and a soil treatment area.

Septic Tank The septic tank is an underground watertight tank, usually with 2 chambers, that receives waste water. It separates the solids from the liquids and stores the solids until they are removed. The liquid, called septic tank effluent, then drains to the soil treatment system called a soakaway.
Inlet and outlet 'T' pipes trap the floating solids in the tank and the manhole facilitates cleaning. Septic tank filters can also be fitted into the 'T' pipes to further reduce the escape of solids into the soakaway.
The size of the septic tank needed is based on the number of bedrooms the house has. A 3 bedroomed house has a minimum 2900 litres requirement, a 4 bedroomed has a 3080 litres requirement, etc.

septic tank filter

Soil Treatment or Soakaway Area The soil treatment part of the typical septic system is a network of perforated pipes or tubes laid on and surrounded by stones or rocks with soil on top. Some rogue traders try to sell crates or tubes instead of rock to disperse effluent from the tank into the surrounding soil, but these are not legal for wastewater.
The design of the soil treatment area (trench, mound, etc.) is based on the soil and groundwater conditions. The soil in the treatment area must not be saturated with water at any time during the year. 1 metre of unsaturated soil below the soakaway trench bottom is necessary to complete the treatment process.
The size of the soakaway treatment area needed depends on the volume of water to be treated and the type of soil on the site. For example, a much larger soil area is needed for a large home or a home on heavier soil than for a small home or one on sandy soil. Clay soils cannot have soakaways as the soil is not porous enough for a soakaway to work, no matter how much land you have available. Pumps and a lift station may be components of a system where gravity flow doesn't work. For example, in soakaway mound systems, a pump is required to provide pressurised flow for distribution of the effluent to a higher level.

Drainage field soakaway plan

How Is Raw Sewage Treated?

In a typical septic tank system, raw sewage is collected by the plumbing in the house and flows to the septic tank. The lighter solids float to the top, forming a scum or crust layer, and the heavier solids sink to the bottom, forming septic sludge. In the tank, organic solids such as food particles and human waste are partially decomposed by millions of naturally occurring anaerobic bacteria. The partially treated liquids, or effluent, then flow to the soil treatment area. Effluent contains pathogens (disease-causing organisms), nutrients, and some fine solids. A thin layer of fine solids, dead bacteria, and soil bacteria, called a biomat, forms naturally where the effluent enters the soil. This biomat eventually restricts the flow sufficiently to keep the soil saturated and the soakaway then fails. You cannot resurrect a failed soakaway, no matter what the advertisements tell you. When they fail, you must install a new one somewhere else.

Why Do Septic Tank Systems Fail?

Failure of your septic tank system means that wastewater may come in contact with people or enter the natural environment without any treatment of the pathogens and toxins. Indicators of problems or a failing system include the following:

  • Sewage backing up to the house
  • Toilets slow to flush
  • Sewage and wastewater visible in inspection chambers (these should be empty)
  • Algal blooms and excessive plant growth in nearby ponds or lakes
  • Sewage smells indoors or outdoors
  • Water or sewage surfacing in the garden or a ditch
  • High levels of nitrates or coliform bacteria in well water tests

Septic tank system failure is normally the result of improper design or installation of the system, overuse of water in the home, or lack of proper maintenance. However, all septic systems have a finite lifespan and 25 years is about the maximum.

Improper Design or Installation

This may be the result of mistakes made by the installers. It may be that the mandatory tests for the water table height and soil porosity were not done. It is also possible that the wrong type of system was chosen for the site and soil conditions (for example,clay soil, high water table, shallow bedrock) or that the house has been extended for more people or to use appliances that the system was not designed for or sized to handle - hot tubs, etc.

Overuse of Water

The typical UK resident (man, woman, or child) uses about 150 Litres of water per day. Systems are sized for typical water use, but abnormally high usage or accidental overuse (such as from leaky taps and toilets) can quickly overload the system. A system partially damaged from improper maintenance may not be able to treat even typical volumes of water. This situation often occurs when a home of one or two people is sold to a family of four or more, causing water use to increase dramatically.

Lack of Maintenance

The solids that accumulate at the bottom of the septic tank must be removed regularly. If excessive crust or sludge builds up, it will begin to enter the soil treatment area and over time will block it. It is recommended that a septic tank be emptied (pumped out) through the manhole, removing all solids, every year. The complete removal of solids from the tank requires flushing and back-flushing between the tank and the tanker several times. The septic tank must then be re-filled with water immediately.

Operation and Maintenance

Correct operation and maintenance will prevent costly repairs and replacement soakaways in the future.

Control water use

  • Repair all leaking taps, toilets, and appliances immediately.
  • Install low water use fixtures and appliances (especially toilets, washing machines and shower heads).
  • Do not let roof drains into the septic system.
  • Wash only full loads of clothing and dishes.
  • Reduce length of showers, depths of baths and number of toilet flushes.
  • Re-route water softener discharge water out of the septic system.
  • Spread water use, such as laundry, evenly throughout the day and week.

Don't poison the system

  • Eliminate use of harsh cleaners, disinfectants, detergents, and bleach. Use steam cleaners and mops instead.
  • Don't put solvents, paints, and unwanted medications down the sink.
  • Keep grease, lint, food particles, cigarette ends, paper towels, disposable nappies, coffee grounds, sanitary products, plastics, and other solid products out of the system.
  • Use only necessary amounts of liquid non-phosphorus detergents and cleaners. (The 'ALMAT' range from ALDI are the best)

Do not use septic additives

It is not necessary to use additives to improve the performance of a septic tank. If the level of bacterial activity is low, it is because disinfectants and other products are killing them. Stop using them. Some additives cause solids to become suspended in the liquids. These solids will end up in the drain field, causing significant damage. Additives do more harm than good.

.Regularly empty and inspect the septic tank The septic tank must be cleaned regularly to remove all solids. Never go into or bend over the septic tank. It lacks oxygen and contains dangerous gases.

  • Always clean the tank through the manhole
  • Always use a licensed professional.
  • Be sure all solids are removed (flush and back-flush).
  • Inspect the baffles to be sure they are in place and functioning properly.

Maintain filters properly

  • Install and clean lint filters on laundry equipment.
  • Clean or replace effluent filters regularly.
  • Investigate alarms on pumps and filters immediately.

Protect the soil treatment area

  • Mow, but do not fertilise or water grass on the soakaway area.
  • Keep all vehicles (cars, tractors, quad bikes, etc.) and heavy animals - cows, horses - off the soakaway area.
  • Do not place gardens, swings, play equipment or sand pits over this area.
  • Do not plant trees and shrubs on or close to the soakaway.