There’s a certain pride that comes with rolling up your sleeves and doing something yourself. Whether it's building a deck, rewiring a dodgy light, or digging a trench for that future veggie garden – Kiwis are good at figuring things out. We’re resourceful. We know someone with a digger. And YouTube has everything, right?

But when it comes to installing your own septic tank – and we say this with deep respect for your number-8-wire spirit – this is one job you absolutely shouldn’t DIY. Here’s why.

It’s not just a tank in the ground

On the surface, a septic system might seem pretty simple: some tanks, some pipes, a hole, maybe a pump. But what you’re actually dealing with is a small-scale treatment plant, designed to manage all the wastewater from your home, safely and sustainably, without harming people or the environment. That’s a big job. And it involves more than just getting the levels right or checking a few council boxes.

These are the kinds of problems we see all too often in the industry:

• Poor soil assessment and undersized soakage fields, leading to effluent pooling on the surface — especially in heavy clay or high rainfall zones.

• Incorrect pipe gradients, which cause blockages and backflow. One wrongly positioned bend can disrupt the entire system.

• Non-compliant installs that skip council approval or engineering signoff. These often come back to bite during property sales or subdivision — requiring costly rework to meet current standards.

• Environmental breaches, like untreated or partially treated effluent entering waterways, which can lead to regional council enforcement, fines, and mandatory remediation.

The risks aren’t just theoretical. Every one of these outcomes has been seen in real projects across New Zealand — and they’re expensive, messy, and often entirely avoidable with the right professional support up front.

A certified drainlayer or wastewater specialist knows how to navigate these factors — designing a system that performs over time, protects the environment, and meets all regulatory requirements. It's not about ticking boxes. It’s about doing it once, and doing it right.

DIY gone wrong: some real-life stinkers

We’ve seen what happens when things aren’t done properly – and trust us, it’s never as cheap or simple as it seemed at the start. Here are some examples:

The “mates rates” mishap: A bloke out in the country got his mate with a digger to help install a tank – no consent, no engineer, no worries... until the system failed a year later. Turns out the soakage trench was undersized, collapsed in heavy rain, and the whole thing had to be dug out and redone. By the book, this time – at triple the original cost.

The uphill battle: Another DIYer “eyeballed” the levels on their pipework. Everything looked fine... until the tank outlet sat lower than the disposal field. Gravity said no. Waste backed up into the house after the first storm, and the family had to move out for a week while a certified drainlayer fixed the fall.

The mysterious summer smell: In one rural neighbourhood, locals kept complaining about a bad odour every time the weather warmed up. Eventually, the culprit was traced to a DIY-installed septic tank discharging into a dry creek bed. The council issued fines, and the homeowner had to pay for a full redesign, consents, and rebuild. Not exactly a summer to remember.

It’s what you don’t see that can cause the biggest problems

Wastewater doesn't just disappear. It soaks into the land, flows into nearby waterways, and can end up affecting your neighbours, your stock, or your own drinking water supply.

If your system isn’t installed properly, or if it doesn’t match your property’s soil type and flow volume, things can go wrong fast – and the fix is often expensive and messy.
We’ve seen the “after” photos. They’re not pretty.

A certified drainlayer knows how to design the system to suit the land, get the right fall and flow, select the correct pipe types and connections, and work alongside councils and engineers to meet all the necessary approvals. It’s not just about compliance – it’s about making sure your system actually works.

You’re not just buying a tank – you’re buying peace of mind

When we install a wastewater system at Waterflow, it’s a team effort. We work with licensed drainlayers, engineers, and sometimes environmental consultants to make sure the whole setup will work properly over time. Because a septic system isn’t something you want to “give a go” and then revisit in five years when your paddock starts smelling or your toilet won’t flush.

You wouldn't fly a plane just because you've watched a few tutorials. The same goes for managing human waste.
It’s easy to underestimate just how technical this job is. But it’s also easy to get the right help.

Your installer isn’t just ticking a box

We’ve worked with a lot of licensed installers over the years – and they’re some of the most solution-focused, skilled, and experienced people out there. They’re not just laying pipes – they’re protecting your property, your health, and the land around you.

It’s why the Plumbers, Gasfitters and Drainlayers Board takes registration and supervision so seriously. If you’re not licensed and you install a system, the legal and environmental consequences can come back hard. But more importantly, you might end up putting yourself, your family, and your neighbours at risk.

So what can you DIY?

Honestly? Planning. Research. Getting the right system for your property. We love working with hands-on people who want to understand how everything works – it makes the job better for everyone. But when it comes time to break ground, you’ll want a registered drainlayer on-site, doing the work right. And in the long run, that’s the best kind of DIY decision you can make.

Want some free advice? Book a site assessment with Waterflow today.