A question I often get asked when I've pumped a septic tank is "was it full?" So here's an explanation of how a septic system works. As you can see the tank must fill to the level of the bottom of the inlet and outlet pipes for it to function. Most household tanks, depending on the size of the family, will refill within a week or so of them having been emptied and will automatically begin functioning without the necessity of any roadkill, molasses, dog biscuits or any other form of starter being added. Your "meat and 3 veg" will do the job.
Septic Tank Maintenance and Care
Contrary to common belief, septic tanks are not maintenance free. However, properly designed septic tanks installed correctly and not overloaded with water or household grease or solids from people using the kitchen sink for garbage disposal normally function well for many years.
Typically, septic tanks are made either of precast concrete or polyurethane/plastic. Most tanks have lids with at least three entrance points, the large central manhole plus an inspection opening above both the inlet and outlet baffles. The baffles (or tees) are installed in order to keep the floating scum (or crust) and any grease or oils from leaving the tank and clogging the absorption surface of the drainage soil in the trenches. In addition to the floating scum, the tanks also contain liquid sewage or "black water" (as opposed to "grey water"), which is what gets displaced through the outlet to the trenches by the inflow of effluent through the inlet tee. Over a period of time, a sludge buildup forms in the bottom of the tank. This sludge consists of the solids that remain after the anaerobic bacteria in the tank breaks down the solid wastes.
The natural process of anaerobic digestion normally does quite well on its own, (unless all occupants of the house are vegetarians) so no chemicals, enzymes, yeast or other additives should be routinely fed into the tanks. Normal household chemicals and occasional use of drain cleaners will not significantly affect tank operation. Fine roots that penetrate porous drain lines can sometimes be controlled by adding copper sulphate crystals.
Monitoring Sludge Depth
Sludge will eventually accumulate in the bottom of all septic tanks and this build-up is generally slower in warm climates than in colder climates.
For the home handyman who's keen to monitor this buildup themselves, the only way to determine the sludge depth is to measure it with a probe inserted through an inspection port in the tank's lid.
There's no point carrying out this job once the tank has become overfull and the toilet has overflowed as there's a fair chance you'll have missed the boat so to speak and damage to the trenches, which can be expensive to repair, could already have occurred
This is not a process which is generally offered by septic tank pumpers, but, if you're keen to self monitor your system in order to determine when to call the pump truck, then you should measure the sludge depth as follows at least once each year with a probe.
To measure the sludge depth, wrap a long stick with a piece of rough white towelling (twitched with wire onto the stick) on one end. Slowly lower the towel-wrapped end of the stick through the large manway through the centre lid or through the inspection opening above the outlet tee (in order to avoid the scum or crust) down to the bottom of the tank. After a few minutes, remove the probe slowly. Black sludge particles cling to the towel and indicate the sludge level in the tank. If the sludge layer is more than half a metre or 18 inches thick then the tank should be cleaned. Many warm-climate septic tanks that are lightly loaded can serve 5 to 7 years for a normal family before cleaning, obviously if there are a large number of people living in the same house then the tank will need to be emptied much more frequently, even every 6 months, especially if the majority of the occupants are constantly at home during the course of the day.
Nevertheless, tanks should be emptied periodically to prevent sludge build-up and damage to the trenches caused by clogging of the soil by sludge being displaced through the outlet.
Measuring Crust Thickness
The floating scum thickness can be measured with a probe. The scum thickness and the vertical distance from the bottom of the scum to the bottom of the inlet tee can also be measured. If the bottom of the scum gets within three inches of the top of the outlet tee, scum and grease can enter the trenches. If grease gets into the trenches, percolation is impaired and the trenches can fail. If the scum is near the bottom of the tee, the septic tank needs to be cleaned out. The scum thickness can best be measured as explained above, however, you would need to know how far the tee extends into the tank.
Tree Roots
Tree roots can enter sewage and trench lines and cause clogging of the lines. Lines should not be placed near trees, and trees should not be planted near lines. In Australia Fig trees and Umbrella trees are known to have some of the most invasive root systems known so can become a serious problem for soakage systems.
Where possible, remove tree roots mechanically or flush copper sulphate crystals down the toilet to help discourage or destroy the roots where the solution comes in contact with them. Some time will need to elapse before the roots are killed and broken off so this is by no means an instant fix for the problem.
Recommended dosage rate of copper sulphate crystals is one kilogram per 1600 litres of tank capacity, so a normal concrete tank would need about one and a half kilograms and a plastic 3500 litre tank would need at least two kilograms. No more than two applications per year are recommended.
The application of copper sulphate must be timed to allow minimum dilution and maximum contact time, or in other words when the inflow of effluent would be at its lowest.
Copper sulphate will corrode chrome, iron and brass, so avoid contact with these materials. Used in recommended dosage, copper sulphate will not interfere with septic tank operation. Neither mechanical removal nor copper sulphate contact is a permanent solution for tree roots. Remove the trees for a permanent solution to the problem.
Physical Damage
Damage to the septic tank and trenches can occur from traffic or wheel loads on the system. No vehicles should be driven over septic tank systems. No driveways, concrete surfaces or asphalt should be placed over trenches lines or the septic tank. If vehicles must cross the trenches, use cast iron pipe or heavy pipe under the crossing.
If the trenches fail
It is sometimes easy to tell when the trenches aren’t working properly. Failure occurs when for some reason the soil is not adequately absorbing the effluent and it may then come to the surface, often resulting in the growth of a lush dark green strip of grass above the trench, which, for those without detailed plans of the premises, will also indicate where the trenches are situated. A black-grey odorous liquid may also be seen at the soil surface when failure occurs. If liquid rises to the surface, a health hazard could exist for children, who should be kept away from the area until the problem is solved.
Apart from our high tropical rainfall which can cause a significant rise in the ground water table, there are a number of problems which can also cause failure of the trenches, (this problem might not always be permanent), including solids filling the septic tank, tree roots, excessive grease and fats entering through the kitchen sink, and overloading by excessive water entering the trenches due to leaking plumbing fixtures such as dripping taps and running toilet cisterns. These problems once diagnosed should be attended to immediately as something as innocuous as a continuous drip from a tap or cistern dribble can saturate the trenches within days and cause at the very least temporary failure of the system.
If a large number of people occupy the house, especially if they seldom leave the premises, there a number of ways to lessen the impact on the trenches through the septic system. Although not always possible due to the existing plumbing of the premises, all "grey water" should be discharged onto grassed or garden areas, this means all shower and basin water.
This practice is totally legal as far as most councils are concerned providing that it's only grey water.
The discharge from automatic washing machines can also have a major impact on trench health as these machines can use up to and above 200 litres per wash which, under normal conditions of a single wash per day, the trenches are able to handle. However, if the machine is being used more than once a day and there are numerous people in the household, then it's possible that the trenches will not be able to allow the large volume of water to soak away.
It is also good idea to ensure any surface water be directed away from the top of the tank itself to prevent the entry of this water into the system and further stressing the trenches.
Preventive Maintenance
Preventative maintenance is the best approach for septic tanks, these measures include but are not limited to:-
Having septic tanks cleaned on a regular basis as this will enable the contractor to report on any potential costly issues regarding the condition of the tank and its contents such as scum or crust buildup, sludge buildup, baffle (or tee) condition, any root ingress through either the pipework or sides of the tank and also any non bio-degradable matter being disposed of into the system.
Monitoring sludge and scum levels in the septic tank on an annual basis. (for the home handyman)
Minimizing grease, solids from garbage disposals, chemicals and other materials. Discharge from grease traps cannot go directly to the trenches unless it goes through the septic tank or alternatively the grease trap is connected to a separate system.
Reducing water flow into septic systems and never emptying water from downspouts into the septic tank. Direct surface water away from the trenches.
Avoiding traffic or wheel loads over the septic tank and trenches. Don't put driveways over trenches or tanks.
Removing trees from the trenches area to avoid tree root problems.
Getting help when you suspect a problem, to minimize the damage.
New systems
Before purchasing a block for home construction check with your local council and have soil tests done if you need to install a septic system. This cannot be overemphasized, especially if the property is close to a waterway as local or government environmental laws may require a stand alone sewage treatment system to be installed which can become an unaccounted for cost factor added to the bargain purchase price.
Conclusions
Septic tanks require reasonable usage and maintenance to ensure efficient operation, however, normal household systems are not designed to endure high inlet volumes caused by constant prolonged usage throughout the day and are unable to handle the same volumes as a town sewage system.
The following suggestions should be followed by all users of septic systems including landlords and their tenants of rented premises.
Repair or report to the landlord leaking plumbing fixtures in order to avoid complete soil saturation of the soakage areas and premature trench failure.
Add water-saving fixtures and shower heads to reduce loading on the soakage areas.
Allow only household liquid waste to be disposed into the system. Put kitchen grease and garbage into the trash not down the sink, in other words wipe all food scraps and oils/grease from plates before washing in the sink to prevent it from entering the septic system.
Septic tanks require periodic cleaning (pumping out) to remove accumulated solids, do not allow the septic tank to fill with solids and overflow into the trenches, if this happens, the soil in the trenches can become sealed/ clogged (water will not percolate into the soil) and is very expensive to repair.
The solids level in the tank should be monitored annually and pumped out before overflow occurs. Unfortunately, as this is the responsibility of the owner, most homeowners will not do this. If checks are not made on solids levels, the tank should be cleaned at least every five years or less depending on the number of occupants of the premises.
It is difficult to predict how fast solids will build up in the tanks due to many factors being involved, however, apart from the maintenance issues mentioned above, the number of people occupying the dwelling will most definitely have a large impact on the frequency necessary.
Landlords should inform lessees of their responsibilities regarding septic systems and also be very aware of the number of tenants likely to be occupying the premises, especially if it is likely that they will be using the septic system constantly during the day, and therefore factor in servicing accordingly in order to avoid expensive rectification of failure of the system.
Finally, the golden rule for any septic system is, if you can't eat it don't flush it. This applies to so called "flushable wipes" pantie pads (surfboards), tampons, (white tail mice) condoms (balloons) and any other items which belong in the trash such as cigarette ends, tea bags, toilet fresheners and numerous other non degradable items which always seem to appear when pumping out tanks.
Cleaning Tanks and costs
Any person who cleans or removes the contents of septic tanks, by law must have all relevant insurance cover and an EPA permit which defines strict removal and disposal methods.
The only acceptable method of disposal of any septic waste is by processing the waste through a registered wastewater treatment plant, or sewage handling facility so by law it's not possible for the contractor to dump it "at the bottom of the paddock" or "spread it around the banana plants".
Councils have a charge or "dumping fee" for the disposal of septic waste and this waste is processed through a specialised receival machine which measures not only the total flow, but also removes the majority of any solids or any other foreign bodies which, as mentioned above, should never have been in the septic tank as it adversely impacts their treatment facility.
This fee is then obviously passed on to the customer as a portion of the total cost. However, providing the tank is being maintained on a regular basis, when the monthly cost of this amount is amortised, it actually works out to be a lot cheaper than being connected to the town sewage system.
I hope you've found this information useful wherever you come from but if you live on the beautiful Atherton Tablelands in Far North Queensland and think your septic tank might need a pump out or would just like some advice then please contact DJ at Tableland Septic Waste for more information.