How to Connect Your Water Tank to Household Plumbing

Installing a water tank on your property is one thing — but connecting it to your household plumbing so you can use rainwater for toilets, laundry, garden taps and irrigation is where you really start making the most of your investment. Whether you’re changing the way your home uses water to save on bills or you want greater self-sufficiency, this step-by-step guide shows you exactly how to connect your tank to household plumbing in a way that’s compliant, efficient and reliable.

Before any plumbing work begins, it’s essential to familiarise yourself with the legal and health requirements involved in connecting your tank to household plumbing.
In Australia:

• Rainwater systems need to be set up to avoid contamination of drinking water supplies and mains systems.
• If your tank will connect to toilets, washing machines or hot water systems, licensed plumbers must complete the installation.
• Cross-connection (where tank water backflows into mains water) must be prevented using backflow prevention devices or air gaps as required by plumbing codes.
• You may also need a Certificate of Compliance from your plumber once the work is inspected — check with your local authority.

Doing the plumbing correctly from the outset protects your household and ensures your system is compliant with the Australian Plumbing Code and National Construction Code.

Before any pipes are laid, think through:

• What you want to supply — toilets, laundry, garden taps, irrigation lines.
• Where the tank is in relation to your house — will water flow by gravity or require pump pressure?
• How many downpipes from your roof will feed the tank — more connected roof area means more rainwater harvesting potential.

Careful planning at this stage makes the actual connection work faster, easier and more cost-effective.

Your water tank must be positioned on a solid, level base ready to receive water from your roof gutters. This typically involves:
1. Connecting downpipes to the tank:

• Use PVC pipe (common sizes 90 mm) and connectors to bring rainwater from gutters into your tank.
• Whether you use a dry system (pipes run above ground) or a wet system (pipes run underground) will depend on distance and aesthetics.

2. Install first-flush diverters and leaf filters:

• These improve water quality by keeping initial roof runoff and debris out of the tank.

Once the pipework from the roof to the tank is completed, your tank is ready for internal connections.

Tank water does not usually run through household plumbing at the same pressure as mains supply. You’ll need a pump system to deliver consistent pressure.
Key options include:

• External pump: Typically more durable and easier to maintain.
• Submersible pump: Installed inside the tank, quieter and space-saving.

Your choice will be influenced by how many fixtures you plan to run from the tank — toilets and laundry will need higher pressure than garden taps alone.

Here’s how water typically gets integrated into your home systems:

Toilet and Laundry Supply

• Your plumber will install a rainwater supply line and may include an automatic switch-over mechanism to mains water if the tank runs dry.
• Ensure appropriate backflow prevention and isolation devices are fitted between rainwater and mains supply lines.
• The plumber will tie this into the existing household plumbing using compliance-grade materials and fittings.

Garden Taps & Irrigation

• Garden taps are usually connected via a separate line from the pump or a dedicated outlet on the tank.
• Irrigation systems may be plumbed in with additional valves that allow you to switch between tank water and mains supply (when dry).

Once your tank fills, excess water has to go somewhere:

• Direct to stormwater system using a pipe that runs from the tank’s overflow to the legal point of discharge.
• Or direct overflow back into landscaped areas that can absorb the extra flow — just ensure it does not damage foundations or create pooling.

The goal is to make sure water is safely managed without causing backyard flooding or structural problems.

After the plumbing and pump installation:

• Your plumber will test each connection — inside and outside — for leaks, pressure consistency and backflow prevention performance.
• Some areas require third-party inspection (e.g., NSW Fair Trading) if rainwater is connected to internal lines.
• Always ask for a Certificate of Compliance once the work passes inspection.
• This provides peace of mind and ensures your system meets all Australian plumbing standards.

Connecting your water tank to household plumbing brings ongoing benefits — and responsibility. To keep the system operating efficiently:
✔ Regularly clean filters, first-flush diverters and leaf screens.
✔ Check tank inlets, outlets and mosquito screens.
✔ Inspect pump and pressure system annually.
✔ De-sludge the tank every few years to remove sediment.

Good maintenance ensures water quality remains high and your plumbing connections stay trouble-free.

Connecting your water tank to household plumbing isn’t just about pipes — it’s about making rainwater a reliable part of your everyday water use. From toilets and laundry to garden taps and irrigation, a properly integrated system can reduce mains usage, save money on bills and improve sustainability — but only if installed correctly and to code.

Working with licensed plumbers and ensuring your system complies with Australian standards protects your home, your family and the longevity of your tank. That’s why The Water Tank Factory always recommends professional installation for internal plumbing connections.

Ready to transform how your home uses water? Contact us today to explore the right water tank and accessories for your property — and start capturing the full benefit of rainwater harvest