Rainwater Harvesting Systems
More, cleaner rainwater from your roof.
Rainwater collection systems for NZ homes
Most rural homes in Rodney and North Auckland live on the rain that falls on their roof. A good rainwater harvesting system collects as much of it as it can, keeps leaves, dirt and droppings out of the tank, and stores enough to get you through a dry summer.
That takes more than a roof, gutters and a tank. Gutter guards, rain heads, a first flush diverter and a pre-tank filter each keep something out, and a calmed inlet and a floating outlet keep the water in the tank clean.
We’ve designed, installed and serviced rainwater systems since 2000, from Mangawhai to Albany, for new builds, existing homes and baches. Rainwater for a school, café or business? See commercial water treatment.
Start with a free onsite visit.
The ultimate rainwater harvesting system
This is everything we’d put into a rainwater system if we were starting from scratch. Not every home needs all of it, and it isn’t always practical or within budget.
The one part you shouldn’t go without is the UV system with its filters (10). It’s what kills the bugs that make people sick. Everything else keeps more dirt out of your tank, helps your filters and UV work better, and helps you manage your water.
Essential
The one part you shouldn’t go without:
- UV system with its filters (10). It kills the bugs that make people sick.
Recommended
In order of importance:
- Maelstrom pre-tank filter (5)
- First flush diverter (4)
Nice to have
In order of importance:
- Digital tank level gauge (9)
- Floating outlet (8)
- Gutter guard (2)
- Rain head (3)
- Calmed inlet (7)
The journey of your rainwater
Each step matches its number on the drawing above. Tap a blue heading to find out more.
1. Your roof
Almost any roof works. Droppings, leaves, dust and spray drift wash off it when it rains. Don’t collect drinking water from roofs with lead flashings, lead-based paint or treated timber shingles. Having the roof washed or treated for moss? Protect your rainwater tank first.
2. Gutters and gutter guards
Gutters need enough fall to drain, so water doesn’t sit in them. Gutter mesh keeps out leaves and pōhutukawa flowers, which stain the water and rot in the tank.
3. Rain heads and leaf diverters
Fitted on the downpipes, they shed leaves and twigs before they reach the pipes, so there are fewer blockages and less sludge in the tank.
4. First flush diverter
The first rain off the roof is the dirtiest. The diverter catches it, then a ball seals the chamber and cleaner water flows on to the tank. It drains itself after the rain.
5. Pre-tank filter
A Maelstrom filter screens the water down to 180 microns before it goes in, keeps out insects and light, and cleans itself.
6. The tank
Sized to your home and set on a compacted base, with a screened overflow so nothing can crawl in. We install plastic and concrete tanks.
7. Calmed inlet
Brings new water in gently at the bottom of the tank, so it doesn’t stir up the sludge that settles there.
8. Floating outlet
Draws water from just below the surface, where it’s cleanest, instead of from the bottom where the sludge sits.
9. Tank level gauge
A digital gauge on the tank sends the water level to your phone, so you can cut back or order a water delivery before you run out.
10. After the tank: pump, filters and UV
Rainwater still isn’t safe to drink straight from the tank. A pump sends it to the house, and sediment filters with a UV system make every tap safe. It’s the one part of the system you shouldn’t go without.
Featured Product
Maelstrom Pre-Tank Filter
Filters rainwater before it goes into your tank, through a 2 mm bucket, a 180-micron filter bag and a mozzie-proof screen. It keeps out leaves, fine dirt and insects, keeps light out of the tank, and suits above- or below-ground tanks. Not sure if it’s the right fit? Call us and talk to our team.
$346.96 excl. GST
How much water do you need?
Every millimetre of rain on a square metre of roof gives you about a litre of water. So a 150 square metre roof collects about 150 litres from each millimetre of rain, less what the first flush diverter takes and what overflows in a downpour.
How much storage you need depends on how many people live in the house, how much you shower, wash and water the garden, and how long a dry summer lasts. As a guide:
- A family of four can use 800 to 1,000 litres a day.
- For a home with 3 or 4 bathrooms and 4 or 5 people, we’d expect 40,000 to 50,000 litres of storage.
- Two 25,000 litre tanks is the least we’d put in for a family home today.
- Collect from every roof you can. The garage and sheds add up.
Running short every summer? A second water tank is often the answer, and a tank level indicator shows how much water you have left, so you can cut back or order a water delivery before you run out.
Wet or dry system?
How the water gets from your gutters to the tank matters.
In a dry system, the downpipes run above ground and fall all the way to the tank, so they empty after every rain. They’re simple and stay clean, but the tank has to be close to the house, so they don’t suit every home.
In a wet system, the pipes run underground and come back up into the tank, so they stay full of water between rains. That lets the tank sit away from the house, but the water in the pipes can go stale and smelly in summer and breed mosquitoes. We fit screens at both ends, a flushing point at the lowest point and a first flush diverter, so stale water doesn’t end up in your tank.
Signs your rainwater system needs work
Gutters overflow when it rains.
Leaves or sludge in the tank.
The water smells or looks cloudy.
Mosquito larvae in the tank.
You run short every summer.
Filters block up quickly.
Stale, smelly water in the pipes.
No first flush diverter.
A leaning, cracked or leaking tank.
Dry systems
- Pipes empty after every rain.
- No stale water or mosquitoes in the pipes.
- Simple, with fewer parts.
- Need the tank close to the house.
Wet systems
- Pipes run underground, so the tank can sit away from the house.
- Tidier, with no pipes across the lawn.
- Need screens, a first flush diverter and a flushing point.
- A wet-dry valve can drain the pipes between rains.
More water, and cleaner water, from the same roof.
Local Jobs – Local Trust – Local Experts
Recent rainwater jobs
A few of the rainwater systems we’ve installed.
Mangawhai: a 30,000 litre tank going into place for a new home.
Mangawhai: laying the underground pipework to the tank while the house was being built.
Tindalls Beach: two new 30,000 litre tanks going in.
Look after your system
A rainwater system needs a little care to keep the water clean. The Ministry of Health tank guide recommends a calmed inlet, a floating outlet and insect screens on the overflow, and:
- Clean the gutters every three months and after storms.
- Check the tank every year.
- Have the sludge cleaned out when it builds up, or straight away if the water turns cloudy, coloured or smelly.
Empty the first flush diverter and clean the pre-tank filter and rain heads when you do the gutters. When we service your filters and UV each year, we check the gutters and tank too.
New build or upgrade?
Building? Talk to us early. We work out the tank size and where it goes, plan the downpipes and overflow, and install the tank, pump and treatment, so your water is sorted before you move in. See rural water supply.
Already on tank water? We start with a Warrant of Fitness check of the whole system, from the roof to the tap, then tell you what would make the biggest difference. Often it’s a first flush diverter, a Maelstrom filter or a floating outlet, and they can all be added to an existing tank.
Making the water safe to drink is the next step: see rainwater filters and tank water treatment.
How we build your rainwater system
Every job follows the same four steps.
1
Free onsite visit
We look at your roof, gutters, downpipes, tank site and how much water you use.
2
Design
We size the tank and plan the pipework, first flush, filters and overflow.
3
Install
Our team prepares the pad with our own digger, places the tank and plumbs it all in.
4
Service every year
We service the pump, filters and UV, check the system, and remind you when it’s due.
Professional installation
Our own registered plumbers design and install rainwater systems across Rodney and North Auckland, from Mangawhai to Albany.
- Tanks set on a compacted base, 100 mm apart, with nothing hard touching them.
- Downpipes, overflow and suction line plumbed in.
- Our own diggers for the tank pad, trenching and tidy-up.
- Old plastic and concrete tanks removed and taken away.
What we supply and install
- Gutter guards, rain heads and leaf diverters.
- First flush diverters and wet-dry valves.
- Maelstrom pre-tank filters.
- Plastic and concrete water tanks.
- Calmed inlets, floating outlets and screened overflows.
- Tank level indicators.
- Water pumps, UV water filters and ozone tank treatment.
Rainwater harvesting FAQs
How does a rainwater harvesting system work?
Rain falls on your roof and runs into the gutters, then down the downpipes, through rain heads, a first flush diverter and a pre-tank filter, and into your tank. A pump sends it to the house, through filters and a UV system that make it safe to drink.
What size water tank do I need?
It depends on your roof, how many people live in the house and how much water you use. A family of four can use 800 to 1,000 litres a day, and for a home with 3 or 4 bathrooms we’d expect 40,000 to 50,000 litres of storage. We work it out with you at the free onsite visit.
Is rainwater safe to drink?
Not without treatment. Rainwater picks up droppings, leaves and dust from the roof. A good collection system keeps most of that out of the tank, but you still need sediment filters and a UV system to make it safe at every tap. See tank water treatment.
What does a first flush diverter do?
It catches the first, dirtiest water off the roof, with the dust, pollen and droppings that built up since the last rain, and stops it reaching your tank. Once its chamber is full, cleaner water flows on to the tank, and it drains itself between rains.
Do I need a pre-tank filter?
We recommend one. A Maelstrom filter screens the water down to 180 microns before it goes into the tank and keeps insects and light out, so less sludge builds up and your filters last longer.
What’s the difference between a wet and a dry system?
In a dry system the downpipes fall all the way to the tank and empty after every rain. In a wet system the pipes run underground and up into the tank, so they stay full of water. Wet systems need screens, a first flush diverter and a flushing point, so stale water doesn’t end up in the tank.
Can I add a second water tank?
Yes. We join it to your existing tank and fit a valve on each, so either can be shut off. It’s the easiest way to stop running out in summer. See adding a second water tank.
How long does a new tank take?
Water tanks usually take 3 to 4 weeks to make and deliver. We book the installation to line up with the tank arriving and the ground being dry.
Do you install concrete tanks?
Yes. Most of the tanks we install are plastic, but we also install concrete tanks. Concrete tank delivery depends on how far the site is from the yard, so we price it for each job.
How often should I clean my gutters and tank?
Clean the gutters every three months and after storms, and check the tank every year. Have the sludge cleaned out when it builds up, or straight away if the water turns cloudy, coloured or smelly.
Don’t just take our word for it…
⭐⭐⭐⭐⭐
“We used Steve and his team from Aqua works to install two new water tanks. From initial consultation to the completion of the job, Aqua works were incredibly professional. … Steve was incredibly well organised, managing the subcontractors (water delivery etc) so that the job ran seamlessly and so that we were only out of water for an eight hour period. They left the site clean and took care to limit the damage to the property from heavy machinery. …”
Blair Russell, 2026
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“Arranged for a visit from Aqua Works to install electronic water level monitoring for a water tank collecting rainwater supply for my rural home. Jakob arrived on time on the scheduled date and quickly, efficiently completed the task in less than an hour. He clearly explained the system operation and answered all of my questions. … Aqua Works also installed the water pump on the same tank a few years ago, which has been working flawlessly. …”
Graeme Lowe, 2026
⭐⭐⭐⭐⭐
“Due for an annual water tank filter service , I was pleased to see Rich again. Such a friendly guy and does a great job. Although they didn’t need it , he explained to me how tanks can be cleaned out different ways and which are the best. Great service from Aqua Works, highly recommended”
Maureen Coupe, 2026
Planning a rainwater system?
Book a FREE onsite visit. We’ll look at your roof, gutters and tank site, and tell you what you need.