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How Does a Septic Tank Work? A Step-by-step Guide with Advice

9 Jan

A septic tank is an underground and watertight container made mostly from fiberglass, plastic or concrete. They tend to be rectangular and are sunk into the ground.

A septic tank will give you a safe disposal of waste water in an eco-friendly way and for this reason they’re widely used in areas with poor drainage or those in more remote or rural locations which are not connected to the sewage network.

Waste from your home or building is flushed out into the tank for it to be treated. The water is then put back into the ground above the tank and the waste is removed. This avoids the need for sewage pipes to be trunked to the property, although in many cases this isn’t possible due to their location.
A septic tank is usually the only sewage option to the property and rarely an actual choice to the property owner over a more efficient, sewage system.

The idea of a septic tank is to allow nature to turn the waste into three layers.

These layers are:

  1. Scum: A top layer where oil and grease naturally floats to the top above all the waste.
  2. Effluent: The middle layer comprises of watery waste called effluent, which is mainly water with some waste particles, and this makes up most of the tank.
  3. Sludge: At the bottom of the tank the heavier waste sinks and forms a sludge.

Much like a modern sewage system, the septic tank is designed to take harmful waste away from the home or building and treat it so that the water can be used once again. It’s a natural process but needs a well-maintained tank and professional care to ensure it’s doing its job.

Here’s a simply step-by-step to explain how the septic tank works

  1. Waste water is flushed into the tank just like it would be into a sewage in a normal domestic situation.
  2. The water runs into septic tank which is a buried (usually in the garden) where it lies with the specific job of holding the wastewater for long enough that the three layers form.
  3. The solids in the waste will settle and naturally sink to the bottom where they form the sludge.
  4. Then the oils from the waste float to the top to form the scum.
  5. Septic tanks will have a filter or outlet pipe preventing the sludge or scum escaping into the drain field area and contaminating the effluent water.
  6. Then the liquid wastewater (called effluent), and only this, leaves the tank into the drain field area.
  7. The drain field is a special treatment area that that’s excavated and filled with unsaturated soil. The water passes through this soil which acts like a filter and treats it before finally allowing the water to be dispersed as groundwater, usually to water or nourish some nearby crops or gardens.

The waste water percolates the soil, giving it a natural way to remove any harmful bacteria that will live in the waste. The main enemy to the health of people and the environment is the ‘Coliform bacteria’ which is found in the intestines and can cause serious illness to the environment and other animals and humans.

The job of a septic tank is to make sure that this bacteria doesn’t get exposed to anyone or anything.

This really useful video explains exactly how your standard septic tank works and gives a quick visual guide to explain the process the waste goes through.



What happens to the scum and the sludge?

Simply put, that’s where we come in. Your septic tank will need emptying every 1-2 years, although this will depend on the number of people in your home or property as this will determine the amount of use the tank has.

A well-maintained tank usually falls into this timescale and this will ensure you’re not going to suffer with any leaks or worse still, an over-filled tank resulting in sewage leaking from the full-to-busting tank.

Water will always find a way and it pays to have a good septic tank schedule and a booked ‘de-sludge’ with a company like us every two years at least.

If you already own a septic tank you’ll probably aware that everything you flush down your toilet or put down the kitchen sink will pass through your septic tank. The following things should be kept out:

  • Food scraps
  • Grease and oil
  • Feminine products
  • Wet wipes
  • Drain cleaners
  • Bleach

If you limit what you put down your drains to waste and water your system will thank you for it!

Other services we offer for septic tanks are:

  • Septic tank pumping and inspection.
  • Residential and commercial septic and holding tanks.
  • Septic line cleaning (NAWT-certified inspector).

Other areas that affect your septic tank

Good maintenance is a must with a septic tank if you want it to perform to its best but there are some other factors that may cause you some issues if you’re not careful.

These can be similar to the following:

  • Tree roots growing into the drainfield or tank.
  • Building or heavy objects over the tank.
  • Excess water or overfilling.
  • Flood water can prevent the water from draining and reverse the process, leading to sewage backing up the pipe.
  • Biomat failure. Over time ‘bio films’ can form on the pipes in the drainfield and can in worst cases render them inoperable leading to big problems. This is best prevented with good pipe cleaning and maintenance.

As with any area of a septic tank it makes a lot of sense to have a maintenance plan in place and keep your eye on the situation and efficiency of your tank. We use CCTV cameras to inspect the tank without causing too much disturbance, which minimises potential problems.

A septic tank is a live system and the bacteria and other elements require the perfect environment to do their thing. A well-maintained tank will do just that.

If you’d like to talk to us about keeping your septic tank well-maintained then please do contact us today.

Tags:Septic Tanks

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How Does a Septic Tank Work? A Step-by-step Guide with Advice

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