If you're looking to install a wastewater system, you’re probably asking yourself — how much is this actually going to cost? The truth? It depends. But don’t worry, our team don’t believe in vague answers. We’re here to break down pricing so you can start budgeting with confidence. No guesswork, no council headaches — just seriously helpful and expert advice for your property.

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What affects the price?

Frustratingly, there’s no flat fee for a wastewater system — it all comes down to what your property needs and the size or number of dwellings you wish to have. Let’s break it down so you know what to expect (and why).

1. Size and number of dwellings

First things first, you need to make sure you’ve got enough water for everyone. Councils (and New Zealand Standards) calculate the size of your wastewater system based on how many people will be using it. They do this by counting the potential bedrooms or estimating the water needs for venues and public facilities. It’s all about making sure your system can handle the load.

2. Treatment level

Think of septic tanks like you would washing dishes — sometimes a quick rinse is fine (primary treatment), but other times you need a full scrub with detergent (secondary treatment). If you're in a sensitive area, you might even need extra filtration to meet stricter standards. What you need depends on your property characteristics and local council rules. Here’s the breakdown:

Primary treatment (basic septic system) – These systems range from the classic septic tanks to the more advanced vermiculture setups, all doing the same basic job: separating solids from wastewater and letting nature do the rest. They’re great for larger properties with good soils and few environmental restrictions, where they can really get the job done without a hitch.

Starting retail price (not including installation): $3000 +gst
Secondary treatment (aerated or vermiculture treatment systems) – These go a step further, treating wastewater to a higher standard with aeration and filtration. They’re often required on smaller sites or in areas with stricter environmental rules.

Starting retail price (not including installation): $12,000 +gst
Want to know what type of system will suit your property? Take our quiz. 

3. Location, location, location

Where your site is located can really impact your costs. If you're in a remote area, materials and labour are going to cost more to get there. Plus, if your site is hard to reach, has steep slopes, or not much room for machinery, it can make the installation a bit trickier, which can add time and money. Here’s what that might look like:

Difficult access – Steep or tight spots can make it tough to get everything to your site. Fortunately, systems like NaturalFlow or BioPod are made of lightweight, durable plastic, so they’re easier to move around.

Flood zones, waterways, or high-water tables – These conditions might need extra engineering to make sure your system works well and protects the local environment.

Restricted access – If there’s not enough space for big machines, we might need to use smaller ones, which could extend how long the work takes and increase costs.

Also, depending on where you are, your council might need you to get a resource consent, especially if your site is small or in a protected zone. That just means more paperwork and extra steps, which can add to the overall cost.

4. Disposal field type

The disposal field is where your treated wastewater is released into the environment, and the type you choose can affect your costs. It all depends on things like your soil, land shape, water levels, and local rules.

Dripline Irrigation Systems – This system evenly spreads water, giving you good control over how much goes where. It’s super flexible and affordable, making it a great choice for most disposal fields.

Soakage or ETS (Evapotranspiration) beds – These are a traditional, low-maintenance option. They’re built to last, but they need good, well-draining soil to work properly. They might cost more upfront to install, but they’re reliable and often the most durable option in the long run.

5. Council consents & compliance costs

Most of the time, you'll need Building Consent for your onsite wastewater system or any drainage work. The cost of consent can vary depending on your Council. To apply, you'll need a wastewater design (also called a TP58 or Schedule 5 in some areas). We can sort that for you in-house at Waterflow, or we can recommend one of our trusted engineers if you'd prefer.

If you’d prefer, we can take care of the whole consent process for you. Our fee for managing it is between $600 and $1500 + gst, depending on the complexity of the project. Further charges may apply for large scale residential and commercial projects. 

So... what’s the price?

To give you a solid idea of what you’ll need to invest, most of our customers budget between $17,000 – $26,000 for a fully installed system.

Here’s a break down:

• A basic primary treatment system, like a simple septic tank or a NaturalFlow vermiculture system, the full installation usually costs between $14,000 and $25,000 +gst.
• A secondary treatment system, like the EconoTreat or BioPod, you’re looking at a full install cost between $18,000 and $30,000 +gst.
• A top-tier tertiary system with UV treatment, the full installation generally runs between $25,000 and $40,000 +gst.

Want to get a personalised quote for your property? Get in touch with the Waterflow team today, we are here to help. 

Wastewater system FAQs

Bringing you clarity

Got questions? We’ve got answers. Here’s everything you need to know before taking the next step with Waterflow.

Can Waterflow handle the council consent process for me?
Yup. If we design your system, we can take care of the paperwork, submissions, and back-and-forth with the council. Our fee ranges from $600 – $1,500 depending on your council.

Does Waterflow offer financing for wastewater systems?
We don’t offer direct financing, but we can recommend lenders who might be able to help.

Can I just use a concrete septic tank?
It depends on your site conditions and council regulations. A proper assessment is key.

What’s the best system for an Airbnb or holiday home?
Go for something low maintenance like a vermiculture system or a septic tank with a large disposal field.

Do you manufacture greywater systems?
Yes, if you want to reuse wastewater from your shower, sinks, or washing machine, we can help.

What’s the cheapest system you offer?
Depending on the drainage characteristics of your soils, a basic septic tank with a trench disposal field can be the most budget-friendly option.

Need a septic tank for your property? Get in touch with Waterflow today for a personalised quote and expert advice.