Land Application Systems

The Biggest Impact on Your Property

In New Zealand, all wastewater systems discharge to land via a land application system (LAS). It’s actually the LAS that has the biggest impact on your property.

It’s why at WaterFlow we don’t just focus solely on the treatment system like others do. We consider your vision for your property first and then find the LAS that will achieve this and finally the wastewater treatment system that will match and meet your needs.

Your LAS or ‘Disposal Field’ has the largest ‘footprint’ of all of the components and is the ‘subject’ of most Council regulations, involving ‘setback’ distances from features like buildings, waterways, flowpaths, stormwater drains, ponds/dams, bores, ground water/water tables, flood zones, boundaries etc… There is also requirements around steepness of slopes to consider which can have a bearing on which LAS you can get consented, on your site, such as irrigation type fields verses soakage type fields.

The Waterflow Team is well versed in all those constraints and options and very passionate about helping you design the ultimate LAS for your property.

Choosing the Right LAS We know choosing the right LAS can be a complexed process to navigate.

This is why we are here to guide you through every step.

The objective of the LAS is to provide further treatment and polishing of effluent by utilizing the soil matrix for assimilation, leading to eventual transpiration or evaporation through plant uptake. Selecting the appropriate LAS (whether it be an irrigation type or soakage type LAS), for your property involves considering various parameters such as planned landscaping and available areas on the site, to site features like, slopes, waterways and flowpaths, boundaries, covenants and flood zones to name but a few.

This is why suggest you get us involved early on in your project, ‘at no cost’ to ensure that the system we design, is in line with the vision you have for your property.

In short ‘Irrigation’ type LAS’s tend to be more cost effective and can be very flexible but do cover a larger footprint then the ‘Soakage’ type LAS’s which are more compact but involve a larger initial investment. Soakage type LAS’s are extremely robust and typically low maintenance going forward but they also have some constraints in certain soil types, especially these with higher clay content.

Regulations and Requirements Land application systems can be installed above or below ground, but councils do have varying regulations and requirements around this.

Typically slopes of less than 10 degrees have little restriction, slopes of more than 25 degrees can be subject to resource consent.

Our slope calculator can help you work out what slope you have.

We know that these can be overwhelming, but with years of industry expertise, we know our way around these regulations and consents and will be here to share our knowledge and support you, so that’s one thing off your mind!

Plants for Your Disposal Area When installing an irrigation system above ground, it will require covering in mulch and the area planted out.

The best plants for wet areas are those with a high transpiration rate, vigorous growth, and water tolerance. Your options are not limited to native plants but since they are more accessible, they are ideal for huge wet areas.

Standard lawn grass is a proven effective high transpiration plant species in such conditions, as are a large number of other plant species seen in typical domestic gardens.

You can find a list of suggested plants for your disposal area here. Or for more information we recommend you contact your local nursery.

Caring for our Shared Backyard We are stewards committed to helping preserve our environment.

At WaterFlow we will always recommend to you the land application system that meets your requirements and contributes to a cleaner New Zealand.

Land Application Types

Biggest impact on your property

The most common method of discharging wastewater to the ground is through an irrigation or soakage system.

PCDI Irrigation Pressure Compensating Drip Irrigation (PCDI) is a flexible irrigation system that requires higher levels of wastewater treatment.

It is commonly required on heavy clay soils where soakage is limited, and it is important that the treated water is spread evenly.

PCDI has small emitters allowing a limited flow, this forces the liquid to distribute across the entire field rather than pooling in one area.
Due to the fine emitters, the treatment plant must treat to secondary level and the lines regularly cleaned.
The PCDI lines can be of varying lengths and run across contour to a certain degree, giving much more flexibility to the layout and shape of the irrigation area.
At the end of the lines are flush taps, that allow the flushing out of any contaminants that might build up over time, it is best done with clean water. At the end of the main feed line is the end flush tap. It is similar to other flush taps, but some systems will have a hose fitting for back flushing properties.
If your irrigation is buried, the flush taps will be found under purple flush boxes. These have a purple lid and sit flat to the ground to allow the area to be mowed.

LPED Irrigation The most robust irrigation system for discharging wastewater is the Low-Pressure Effluent Distribution (LPED) irrigation.

This is a favourite of ours, as it is the most robust irrigation system available. Using larger 25mm distribution laterals with drilled holes, it is much less prone to blockage and crushing. These larger orifices are covered with a unique and innovative ‘squirt guard’ designed and developed by Waterflow. These systems do require a rectangular area and must run level with the contour, which can limit options of where they can be placed onsite.

Lines of equal length are laid 1-1.5m apart (spacing is dependent on council regulations) on a level contour and they can either be covered with mulch or buried in the topsoil.
The laterals are fed from a manifold at the head of the field, ensuring an even distribution across the field.
At the end of the laterals are flush taps, that allow the flushing out of any contaminants that might build up over time.
The size and number of the holes is calculated by our design technicians for each project. Innovative squirt guards developed here at WaterFlow, clip over each hole to spread the effluent.
Larger laterals and orifice sizes mean robustness and less prone to blockages.

Soakage Systems Soakage systems rely on the earth’s ability to soak up the discharged water, so they are better in ground with a lower clay content. Evapotranspiration can also be utilised, to assist the take up of moisture.

They use higher loading rates than irrigation systems and can reduce your discharge area by up to 50% or more in suitable soils.

These are the most robust LAS systems utilising the earths natural ability to soak up discharge water, using large holes in the dispersal pipes rather than small orifices (like irrigation types), meaning there is virtually no maintenance required and much less chance of blockages over time. Of course, along with the benefits, these systems do have a higher initial investment because of the machinery and materials required to install them.

ETS Beds Evapotranspiration Beds (ETS Beds) are a low-pressure irrigation system laid through a mounded soakage bed to enhance water shed.

These beds are normally between 0.5 – 3.0m wide and 0.45m deep and are filled with drainage metal, in which the effluent is discharged using a low-pressure distribution system. The bed is formed with a slight mound and densely planted, across the entire bed, to maximise evapotranspiration and achieve great hydraulic absorption, especially in clay bound soils. These LAS’s can be loaded at a much higher rates than irrigation types, thus reducing the land application area quite significantly in a lot of applications.

Conventional Soakage Bed These are much the same as an ETS bed. However, they can also be constructed with drilled 100mm PVC, so more robust than ever.

Across soakage bed does not require mounding like an ETS bed and can be just grassed, so can have less visual impact on the property, though it is important to remember that these are only suitable in well-draining soils. With these beds being normally between 0.5 – 3.0m wide (though can be wider in some jurisdictions) and 0.45m deep, they can typically sustain higher loading rates, which in turn minimises area required and site impact.

Conventional Soakage Trench Soakage trenches are much the same as soakage beds, however they are no more than 0.5m wide.

There are a few variations to these, such as sand trenches and deep trenches. Conventional soakage trenches are not so commonly used and depend on council regulations as to their use. If you’re unsure, then get in touch with us early on in your project and we can help you.

Raised Mounds Similar in principle to ETS beds, these are built up and constructed above ground rather than being dug in. Their purpose is to minimise the possibility of groundwater contamination.

Raised mounds are ideal if there is an elevated water table or a flood prone area, where it is necessary to lift the height of the discharge.

Boreholes Deep bore holes are typically 0.6m in diameter and 6.0m deep, the number of holes is determined by a four-hour soakage test. The boreholes have a discharge pipe down the centre and are filled with coarse aggregate.

Since these require resource consent and aren’t a permitted activity under any council in New Zealand, boreholes are only used on small sites with very limited options for discharge.

We're here to help, get in touch with us to Get a Free Site Assessment as early into your project as you can, and we can recommend the best land application system for your site or property.

Land Application Systems