It’s often thought that septic tanks are the cheaper way to go, compared to treatment systems. Not necessarily.
In our experience, septic tanks offer little price benefit when it comes to installation. They are predominantly concrete so require good access and a Hiab to position them. Plastic tanks are available for more difficult sites, but they do traditionally come at a higher price, depending on size.

The overriding consideration if using a septic tank is size both in tank sizing and disposal field sizing. Size is the biggest contributing factor to minimising any risk of environmental harm and a ‘smelly’ backyard, due to the minimal treatment a Septic Tank provides.

If your site is suitable; Waterflow has many options available and will step you through all the necessary calculations, to ensure you choose a size that is truly fit for purpose and sustainable.

Due to the distinct ‘septic’ odour and low levels of treatment a much more robust land application system must be considered. Effluent should be discharged into the ground via a soakage bed system – these require excavation and more material so do increase initial investment.

The principle of a septic tank is this: the wastewater all enters a tank of one or more chambers, in each chamber the solids settle to the bottom and the scum floats to the top. The clear water in the middle then passes to the next chamber and finally out to a soakage area.
Anaerobic bacteria inside the tank break down solid matter at a very slow rate, therefore the solids accumulate in the bottom of the tank and require periodic removal (suck outs).

The discharged water has no large solid matter but can contain various contaminants; the final and main treatment occurs in the soils where the effluent is discharged. While the settling process and anaerobic organisms provide Primary Treatment, the wastewater is not cleaned nearly as thoroughly as it would be using a vermifiltration or aeration system.

Understanding these strengths and weaknesses can help homeowners make informed decisions about installing and maintaining septic systems, ensuring they function efficiently and safely for the long term.

Some old septic tanks have no outlet filter, allowing solid material to exit the tanks and enter the land application system. This leads to blockages and results in backed up drains and sewerage overflowing onto your property.

Most old septic systems rely on a trickle discharge, essentially what goes in comes out. Since the land application system is only receiving a small amount of water at a time, it tends to soak away at the beginning of the soakage area; until the constant flow causes a build-up of slime and sludge and blocks the soil, then it progresses along a bit further; this is called ‘creeping failure’. Over a number of years, the entire area will block up.

We can reinstate your land application system to its original state, as long as we know where it is and how big. If the area or location changes significantly, a building consent will be required, otherwise it can be done as repair work. We will dig it up and use new materials to reinstate it.

In many cases, the most future proof option is to bring the land application up to standard and get it approved by council, as this will improve the current operation and future sale value of your property. By doing this we can also add a dosing module to the septic system, improving the loading of the soakage and increasing its life span.

Most old septic tanks rely on a trickle discharge, which can cause complications.

If there is high ground water, it can flow back through from the soakage into the septic. This typically occurs on flat sites where the water can’t get away easily. In this situation, large rain events can prevent the septic discharging correctly, in the worst case resulting in sewage overflowing out of the tank onto your property, which is definitely not what you want to happen.

This can be remedied by adding a dose tank to the end of the septic and pumping it into the soakage area. The pump forces the water into the soakage area, where it is unable to return to the tank.

We also have smaller gravity dosing modules to improve the dosing of soakage areas.