What is the best wastewater system for a small section?

When you live in town, wastewater leaves your property through the public sewer. On a rural section without a sewer connection, your own system has to handle that job.

You need space for two main parts:

• The treatment system: This receives wastewater from your toilets, showers, kitchen and laundry and treats it before it goes out to the land.

• The disposal field: Also called the land application area, this distributes the treated wastewater into the soil through a designed layout of pipes, beds or trenches.

Think of them as two parts of the same job: treating the wastewater, then giving it somewhere suitable to go.

Finding room for a tank is only part of the answer. On a small section, fitting the disposal field is often the bigger challenge.

There’s no single field size that works for every small section. The area needed depends mainly on how much wastewater your home could produce and how much your soil can safely receive.

That means two houses with the same number of bedrooms can need different-sized disposal fields.

Your designer will look at:

• The number of bedrooms: This helps establish how many people the home could accommodate and the wastewater volume to allow for.

• The soil: Some soils absorb water more readily than others. Soil depth and the level of groundwater also matter.

• The disposal method: Drip irrigation, beds and trenches distribute water differently, so their space requirements differ.

• The site layout: Slopes, buildings, boundaries and waterways all affect where the field can go.

100 m² per bedroom can be treated as a rough early planning allowance. But before you commit to a house layout, have the usable wastewater area checked. A patch of empty land on a plan isn’t automatically suitable for a disposal field.

Because the wastewater system needs to suit the home over its lifetime, including future households.

You might be a couple building a four-bedroom house, with one room for guests and another for the occasional burst of enthusiasm on the exercise bike. The next owners might use every bedroom.

Residential wastewater designs therefore generally use bedroom numbers and the applicable occupancy allowances, rather than relying only on who is moving in first.

Your designer turns that into a daily design flow: the amount of wastewater, in litres, that the system needs to manage each day.

A smaller section doesn’t reduce that amount. And choosing a smaller tank won’t reduce what comes down the pipes.

It can open up different design options, but it doesn’t automatically mean a smaller disposal field.

The treatment system improves the quality of the wastewater. It doesn’t make the water disappear. Your land still needs to receive the volume coming from the house.

Depending on the site, a higher level of treatment may allow a disposal method that makes better use of the available space. For example, a designed drip-irrigation layout may work around suitable planted areas.

But cleaner wastewater doesn’t change clay into free-draining soil. Treatment quality, soil conditions and the disposal design all need to work together.

Once your designer knows what the land can accommodate, they can recommend a treatment system to match.

NaturalFlow, BioPod and EconoTreat may all be worth considering. The right choice depends on the treatment required, the disposal method, installation access and how you intend to use the property.

It’s also worth understanding the ongoing servicing and power requirements before choosing. A system needs to fit your everyday life as well as your site plan.

The useful question is:

“Which complete wastewater setup will work best for this house on this land?”

That gives you a much better starting point than comparing tank dimensions alone.

The actual area depends on how much wastewater needs to be discharged, the soil’s ability to absorb it, the treatment level, slope and the disposal method.

You may also need room for separation distances from boundaries, buildings, waterways and other features, plus a reserve area where required. Those requirements can affect how much usable land you need beyond the field itself. 

This is why it pays to plan wastewater early. The house, driveway, shed and pool shouldn’t get every good spot before the disposal field gets a look-in.

The disposal field’s footprint isn’t the only space to allow for.

Your designer also needs to check setbacks, which are the required separation distances from features such as buildings, boundaries, waterways and bores.

Depending on the site and local requirements, you may also need a reserve area. This is suitable land kept available in case a replacement disposal area is needed in the future.

Access matters too. The treatment system needs to be accessible for servicing and any required pump-outs.

These details are much easier to accommodate while the house, driveway and garage are still lines on a drawing.

Get a wastewater site assessment before you finalise the layout of your home. If you’re buying a small rural section, it’s always good to establish what wastewater arrangements are feasible before committing.

Give your designer the proposed bedroom count, a site plan and any plans for future additions, such as another dwelling.

They can then assess the soil, identify suitable disposal areas and work out which treatment options fit. Site and soil conditions are central to designing an appropriate onsite wastewater system.

A small section can still have a workable wastewater solution. The key is to give it a place in the design early, while there’s still room to move things around.