Living with a Septic Tank System

Septic Tanks 101

Lucky you, you have your own underground sewerage treatment plant

If you are moving to the country from the city chances are you will be encountering your first septic tank system, unless you are old enough to remember having one in the back garden when you were a child. I have distinct memories of the terrible smell emanating from these unpleasant storage tanks when they were well due for emptying, and watching in amazement as the septic truck suction hose bounced around the garden collecting its putrid load. I also have a distinct memory of a septic truck driver standing over the open septic tank examining the progress of the job, while he ate a sandwich. I do not think he washed his hands before he had his lunch, but is that even relevant? The man was consuming food while he breathed in raw sewerage and looked at the sludge in the bottom of a shit tank.

Do not dread the possibility of buying a property with a septic tank. Having a septic tank that is well maintained and cared for is an inexpensive and easy way to manage household waste water when you are not able to be connected to a deep sewerage system. A new septic system should last at least 30 years and require emptying every 2-5 years, depending on usage. You do not need to fear them failing and sending septic water into your house or smelling offensively if you follow a few simple guidelines. Neither do they need frequent pumping and emptying or expensive additives to keep them working properly.

Most buildings that are not close enough to a major centre to be connected to the magical public deep sewerage systems where the refuse is whisked away to a treatment plant to be dealt with by other more qualified people will usually depend on septic systems to treat and dispose of wastewater. This is a rather unfortunate state of affairs. While we all need somewhere for our waste products to go that will keep them out of sight and smell of us as we get about our daily activities, septic tanks can be quite problematic and potential environmental pollutants if not managed well. Repairing damaged systems is time consuming and can be costly. Replacing old or malfunctioning septic systems is very expensive. It cost us $7,000 to have our new system installed.

Management is vital to ensure a long lasting and safe septic system. A faulty septic system may result in damage to your property, the possibility of causing you and your family ill health, the potential to spread disease, and they can also contaminate ground water supplies. Worst of all faulty tanks smell and can send septic water back up your drains and into your house, possibly while you are having a dinner party - too unpleasant to contemplate!


How a Septic System Works
A septic system is just a storage and processing unit for your household waste water and its contents. It has two basic parts: the septic tank to hold the waste water and solid matter and the leach drains to allow the excess water to be absorbed into the soil. The tank can consist of a single tank or a tank made up of two compartments, with a dividing wall in the middle. The tanks with two compartments work better at keeping the solids in the first compartment so that they are less likely to end up in the leach drains. Most tanks are cylindrical in shape and are made of concrete, fibreglass or plastics. If the previous owner did not tell you where the septic tanks were, you will find your tanks by searching for the round concrete, fibreglass or plastic lids that will be sitting just out of the ground. Usually they are very obvious, but if you cannot see them start your search near the building at the site of the major pipe work exit (the toilets and bathroom). It will be around there somewhere! You may also be able to find the leach drains first and work your way back to the tank- look for areas of good grass or plant growth in an otherwise less lush area.

Waste water and the solid matter in the waste water flow from the building into the septic tank via the household drainage systems. The liquid usually hits a baffle which slows the liquid flow into the tank. This is to reduce the disturbance of the sludge on the bottom of the tank. The idea is to keep the solid matter in the tank and allow the water to flow into the leach drains to be filtered by the soil. You do not want the solids to escape from the tank. It is the solids that are pumped out of the tank and removed every few years.  Once in the tank most solids sink to the bottom of the tank and are reduced to a sludge by the bacteria which live in the tank. Some of the solids, such as greases and fats, will float and form a layer of scum on top of the water. The exit outlet which allows the water to flow into the leach drains also contains a baffle which helps prevent solid matter passing out of the tank. The free water will flow into the leach drains where it will be absorbed into the soil, and filtered through the soil and further decomposed by the bacteria in the soil. This water will eventually make its way to the ground water supply.

Solids that are not decomposed remain in the septic tank and if they are not removed by periodic pumping and emptying of the tanks, the solids will accumulate and eventually overflow into the leach drain.  This is not desirable and can block the leach drains and cause your system to back up.
It can also lead to bacterial contamination of the soil around your leach drains. As the sludge layer builds up in your septic tank the time available for the liquids to separate from the solids is reduced and your tank may over flow or back up and the flow may come out of your household drains. This is very bad news. Nobody wants to see raw sewerage floating about in their kitchen sink, or even to smell sewerage wafting up the pipes and into the house.

Most septic tanks must be pumped once every three to five years, depending on tank size, water usage and the number of people who live in the building. You can reduce the amount of waste water flowing into your system by installing a grey water system to take water from the shower and laundry and storing it in a separate grey water tank where it can be used to water your garden. Even this water has potential hazards and must be managed correctly to prevent the possibility of ill health to you and your garden.  It is far better to send as much of the grey water away from the septic tank, rather than in to the septic tank. It will help reduce the possibility of problems with your tank.  All black water -water from the toilet and usually water from the kitchen sink (as it is full of food particles and fats and greases which will adversely affect your grey water tank and system) must go to the septic tank system. You can reduce the amount of water from the toilet entering the septic system by using a dual flush toilet or minimising the amount of times you flush. You do not need to flush after you have passed urine. As the old saying goes- “If it’s brown flush it down, if it’s yellow let it mellow” If you do not have a grey water system you can reducing the amount of water flowing into your system by reducing shower times, not running taps unnecessarily and using a water efficient dishwasher once a day or minimal water to wash up also helps reduce the load on your tank. You can feed your washing machine hoses straight out onto your lawn, as long as you use a low phosphate (or phosphorous) and low sodium washing powder and move the hose about every now and then. Some native Australian plants will not enjoy the grey water- check the health of your plants and move the hose accordingly.

How will you know when the tank needs emptying?

Warning Signs of an overloaded or over used tank are septic smelling odours coming from the drains or tank, evidence of sewerage on the surface around the tank or drains, back up of drains and pipes, slow draining pipes and gurgling sounds in the pipes. Lush green vegetation over the leach drains usually indicates that the drains are full of water. Assess your water use and try to reduce the amount of waste you drain into the tanks. Draining large amounts of water into your tanks at any one time can also lead to overflow problems. This can occur if you have a party and the toilet is used in excess, if you have guests staying over who have long showers or if you do several loads of clothes washing on any one day.

These signs do not necessarily mean your tank needs emptying. Your tank may be unable to process large amounts of excess water flowing into it at a particular time, but otherwise, if the water is used wisely, it is able to cope well with the flow. Overflow of fluid from the tank and excess water in the leach drains may cause bacterial contamination of the soil around the drains and tank.

You will need to have your tank checked every year to see where the level of the solids are in the tank. This is best done by a licensed plumber as the contents of the tank are not good for your health! The gases that accumulate inside the tank are toxic and the effluent in the tank is brimming with bacteria. If you fell in you would never feel truly clean again. Never climb inside the tank! The toxic fumes and low levels of oxygen inside the tank can suffocate you. If you choose to measure the sludge depth and the scum mat thickness yourself before you decide to call the sewerage collection truck in, you can do so by making a homemade probe with depth indicators drawn on the side. Stand outside the tank to do this. Make sure the probe is long enough to touch the bottom of the tank while you are standing outside the tank. Do not lean in! The tank may be quite full of water with the scum mat floating on top. This does not necessarily mean your tank needs emptying. Push the stick straight down to the bottom and withdraw it straight up. The sludge will stick to the probe like the sticky stuff it is, and you will be able to measure it. If you want to be complicated about it, you can follow these guidelines: The tank requires pumping if the top of the sludge deposit is within 30 cms of the outlet baffle, the bottom of the floating scum mat is within eight cms of the bottom of the outlet baffle, the top of the floating scum mat is within three cms of the top of the outlet baffle or the floating scum mat is more than 30 cms thick. Alternatively, you need to empty your tank when to sludge layer fills 1/3 of the tank. The terms sludge layer and floating scum mat are as foul as the actual things they describe- you would be well advised to simply call out a professional and have him deal with it all. Even if the tank does not require emptying you have saved yourself an unpleasant and potentially hazardous job. Once at your house the septic tank collection truck driver will probably empty what you have in your tanks anyway. He may even eat a sandwich while he chats to you. Hopefully he will not offer you one as refusal may offend. In small towns, where contractors are not available, the local Shire usually has a septic tank emptying service. You should never empty your own tanks. It is a terrible health hazard and the effluent from the tank must be disposed of in an approved manner. You cannot simply spread it out over your pastures or empty it into the bush. You must be very responsible when you are dealing with such hazardous waste.


The leach drains
The leach drains receive the waste water from the tanks. They are not designed to handle the solids. Leach drains are a network of perforated pipes laid in gravel-filled trenches in the soil. Wastewater makes its way through the perforations in the pipes, through the gravel layer, and into the soil.
The soil below the leach drains provides the final treatment and disposal of the septic tank effluent. After the effluent has passed into the soil, most of it filters downward and outward, being further filtered by the soil and broken down by microbes in the soil. The waste water eventually makes its way into the ground water supply.

The leaching bed is a soil filter which uses natural processes to treat the wastewater from the septic tank. Contaminants in the wastewater include solid and dissolved organic matter.  nutrients in the form of nitrogen and phosphorous and harmful bacteria and viruses which are always present in waste waters and faecal matter. A layer of bacteria forms at the bottom and on the sides of each leach drain trench and it is in this layer where much of the further breakdown of the effluent happens. This bacterial layer is known as a  biomat. Bacteria in the biomat layer and surrounding soils digest and breakdown the organic matter in the wastewater as their food source. These bacteria also change ammonia nitrogen to the less toxic form of nitrate-nitrogen. Harmful bacteria and viruses present in the wastewater are largely removed in the leaching bed through filtration and environmental exposure to heat, drying conditions of the soils, other microbes which prey on them and salts etc in the soils .The soil bacteria which perform the treatment require oxygen so it is important that the leaching bed is not installed in soils that are frequently saturated by surface water run-off or a high groundwater table. It is not desirable to have your leach drains or septic system installed in an area with a high water table- the tanks may fill up with the ground water and the filtration of the effluent via the percolation through soils before reaching the ground water supply which is required to ensure it is properly broken down into harmless components will not be assured. The same is true if the ground around your tanks and leach drains are regularly saturated by surface water run-off. The soil around the leach drains best filter the effluent when it is dry and permeable. The leaching bed soil must be adequate enough to retain the wastewater for long enough to allow treatment by the biomat to happen, while at the same time be permeable enough to allow the wastewater to infiltrate into the ground and be treated by further filtration. Because the bacteria require oxygen to perform their duties, the leach drains should never be covered with paving, concrete, plastic or other substances that will reduce oxygen in the soil.

Reasons to consider alternative septic design include:

If you have poor soils with very low drainage rates or no soil drainage (heavy clay soils) or too fast drainage (very sandy soils) you may be better off considering an alternative to a conventional system. Wet grounds with high groundwater levels or sites subject to heavy surface runoff may also make conventional systems less functional.

Other problems can come from very rocky building sites or sites with bedrock which means there may not be enough topsoil to treat and dispose of wastewater. A steep site may also make installation of a traditional leach drain bed difficult.

 If the site where the septic tank needs to be installed is very small you may not have enough room to accommodate the required leach drain beds.

Other options

Here are brief descriptions of systems you can consider as alternatives to conventional septic systems. Not all of these systems will be permitted in your area and you will need to get Shire and/or environmental health approval before you install any of these systems. I have not used any of these systems and so cannot vouch for any of them. If you like the idea of trying any of these systems, do your research and see if they suit your location and situation.

Aerobic septic systems

This is an alternative to conventional septic tanks systems using natural processes of settling and filtration in an environment rich with oxygen loving organisms beneficial to the breakdown of waste.

Household waste water drains into the septic tank where solids are settled to the bottom then the water waste is pumped to a secondary treatment tank rich with aerobic (oxygen loving) microbes which breakdown the effluent to harmless components. Many of these systems are fitted with an air blower or pump to feed oxygen to the tank. There are several varieties available, some use air pumps others use specially designed growth mats and some just use a more elaborate aerobic sand filter system, similar to the leach drain sand bed.

These systems treat the water to a higher level than conventional septic tanks and allow the waste water to be discharged from the treatment tank over smaller areas. They may be a good alternative if you have saturated soils, heavy clay grounds or a high ground water table.

Raised Bed and Septic Mound systems

 These are similar to conventional systems, but which require extra steps of soil preparation or the necessity to bring in soils and fill to treat effluent. With this system the drain beds are raised up above ground level and the effluent is then allowed to run onto the specially designed drain filed which is made of absorption and filtering soils and materials which allow it to filter correctly before it reaches the normal soil level. Effluent may enter the mound by gravity if possible, or it may have to be pumped up into the mound. In this latter case the pump would usually be placed in a second septic tank which receives clarified effluent from the primary tank, where the solids are allowed to settle.

Advanced Material Media Filtration systems

Media filter septic systems use a conventional septic tank followed by any of several methods to further filter and treat septic effluent before it flows to the soil or waterway. Examples of these are: sand beds, filter beds, peat filters, synthetic textile filters, trickling filters, and foam media filters

Wetlands and Constructed Wetlands

This is also called a pond system, reed pond systems and lagoon systems and it relies on evaporation, absorption and transpiration as well as filtration through the soil and microbial breakdown. Waste water is collected in a septic tank and the solids settle to the bottom of the tank. The waste water flows into a pond where it is exposed to sun, air and bacterial action. It is filtered through reed beds and/or the soil to further break it down.

Disinfection System

 Effluent is treated by disinfecting chemicals such as chlorine, ozone or by UV light. The treated water is then discharged into the soil or waterways.

How to use your conventional septic system correctly

In order to have the fewest problems with your system and to have a system that works well for many years, you need to follow a few simple guidelines.

Certain things should not be sent to your septic tanks. Fats and greases should not be poured down your sink. Instead, allow them to cool and collect them on paper towel or newspaper and place in the bin. Fats and grease will float on the top of the effluent in the tank and help form the scum mat. The only solid matter that should be put into the tank that does not come directly out of the human body is toilet paper. Do not flush tampons, sanitary pads, wound dressings, baby’s nappies cotton buds, condoms or anything else down the toilet.  Wrap these items and dispose of them in the rubbish bin. These items take too long to break down and help form a large scum mat that may lead to blockage or more frequent tank emptying. Strong chemicals, such as paint thinners,petrol, poisons, pesticides, solvents, nail polish remover, paints, and caustic drain cleaners should not be sent to the tanks. The tanks rely on a healthy microbial population living down there to break down the solid matter to a sludge. If you send strong chemicals in to your tank you may kill these essential microbes and your tank may then fail. You can use disinfectants and bleaches and toilet cleaners as long as you follow the manufacturer’s instructions and dilute them as required. It is probably not ideal to pour undiluted bleach straight down the drains. Look for products that are safe for septic systems.

In sink garbage disposal systems are not septic tank friendly. You do not want to be sending food waste down to your tank. Dispose of food waste in the rubbish bin or better still in a compost bin. The less solid matter you send to your tank the better.

Your tank can be overloaded and not be able to cope with a rapid amount of fluids released into it. If large amounts of water are sent to the tank over a short period of time, the excess water may flow, un settled, into the second chamber or into the leach drains carrying solid matter with it. This solid matter may clog your leach drain system and cause water backup. You need to plan to reduce your water use and to spread your water use out over the day and over the week. Spread showers out over the day. Have short showers. Do not flush the toilet if you have just passed urine. Install a dual flush toilet and use the half flush whenever you can. Spread your laundry loads over the week- don’t do them all on one day. Do not drain several outlets into the tank at once. Think about how much water you are sending to the tank- be aware of it and mindful of it. Your system can suffer overload if you have an increase in people who are using the system, such as when guests come to stay or if you have a party. The less water you send to your tank the better. The longer the first compartment has to settle the solids to the bottom and begin the work of breaking them down, the better your tank will work. The more water that is sent to the tanks the less time the first compartment has to settle the solids before it overflows into the second compartment. Think seriously about installing a grey water system to take the load off of your septics. This way shower water, water from the bathroom sink and laundry water can be collected outside the septic tank and used to water your garden and lawn- as long as your local government allows you to do this. By doing this the only water going to your septic tank is the black water- kitchen water and toilet water.  Of course, don’t allow surface run-off or water from gutters to run into your tank!

You do not need to add any ‘enzyme’ products or septic tank ‘starters’, ‘conditioners’ or ‘sweeteners’. There is no evidence they actually help and if you follow the guidelines above, you will not need them.

Care of the Leach Drains

The leach drains are pretty much maintenance free, however you do need to be aware of what can impair their function. Do not drive vehicles of any kind over the drain system as you can cause the drains to break.

Do not cover the drain field with concrete, pavers, decking or plastic as this can reduce the amount of oxygen the microbes in the soil have access to and then the waste products will not break down properly.

Don’t plant trees near the leach drain as their roots will enter the drains and damage or block them. Plant grass over the drains but never water this grass. The excess water will interfere with leach drain absorption.

Don’t allow surface water run-off or gutters to drain onto the leach drain area as this also will fill up the drains and interfere with the drains function of breaking down the contaminants in the effluent from the septic tanks.

Mark out the boundaries of your leach drains so you do not damage them in the future by forgetting where they extend to.

Your leach drain system should last around 20 years before it needs replacing, although the drains themselves may become clogged by the biomat and need cleaning or replacing.

So now you are a full bottle on septic tanks! I bet you are well pleased with yourself. I hope you and your tank have many happy, uneventful years together!