Rainwater tanks are one of the easiest wins for an Illawarra household — high annual rainfall, big roof catchments, and BASIX rules on new builds that already require one. But the plumbing side decides whether your tank is a feature or a hassle. Here's how we approach rainwater tank installs in Shellharbour, Kiama, Albion Park, Flinders and Shell Cove.
How big a tank do you actually need?
For a typical Illawarra family using the tank for toilets, laundry and garden, a 3,000–5,000L slimline poly tank is the sweet spot. Bigger isn't always better — you only get the benefit of capacity if you're using the water, otherwise it sits and stagnates.
- 1,500–2,500L — garden-only use, courtyards, small block
- 3,000–5,000L — toilet + laundry + garden, average Illawarra family home
- 5,000–10,000L — large block, multiple bathrooms, or off-grid intent
- 10,000L+ — acreage, rural Kiama hinterland, full-house supply
First-flush diverters and leaf eaters
The first few litres off your roof carry the worst of the dust, bird droppings and leaves. A first-flush diverter dumps that initial dirty water before it reaches the tank — non-negotiable on every install we do. Pair it with a leaf eater at the downpipe and your tank water stays clean for years with almost no maintenance.
Connecting tank water to toilets and laundry
BASIX-compliant rainwater connection to toilets and the laundry cold tap is the highest-value plumbing work we do on tanks — it's what shifts the tank from 'occasional garden bonus' to 'meaningful water bill reduction'.
The install involves a rainwater pump (usually a quiet pressure pump with a built-in controller), a mains backup valve so you never run dry, and a clearly-labelled rainwater line into the house. Every fitting downstream of the tank needs to be marked as rainwater under NSW plumbing standards.
Council & development rules in Shellharbour and Kiama
Most tanks under 10,000L on residential blocks are exempt development under the State Environmental Planning Policy — no DA needed. But you still need to follow setback rules (typically 450mm from boundaries for tanks under 1.8m high) and you must use a licensed plumber for any potable connection or indoor connection.
New builds in Shellharbour and Kiama LGAs typically have a rainwater connection requirement under BASIX commitments. If you're renovating, BASIX may trigger again — we can help you check before you spec the job.
Backflow prevention
Any time a rainwater system connects to the same property as a mains supply, a backflow prevention device is required to stop rainwater contaminating the Sydney Water mains. This is mandatory and annual testing applies to most setups — we install, test and certify in one visit.
Frequently asked questions
- Do I need council approval for a rainwater tank in Shellharbour?
- Most residential tanks under 10,000L are exempt development — no DA required — provided you meet height and boundary setback rules. The plumbing connection inside the house still has to be done by a licensed plumber.
- Can I drink rainwater from my tank?
- Legally yes if mains water isn't available, but in the Illawarra where Sydney Water mains supply is reliable, most homes use rainwater for toilet, laundry and garden only. If you want potable use, add a UV steriliser and sediment filter — we install both.
- What size pump do I need for a rainwater tank?
- For a typical home connecting to two toilets and the laundry, a 750–1000W pressure pump with auto-stop control is the standard. Quiet, low-energy and good for 15 years if installed under cover.
- Will the tank water cut out if it runs dry?
- Not if it's installed with a mains-switch device — these automatically swap the supply to Sydney Water mains if the tank empties, then revert to rainwater once it refills. We fit one on every connected-tank install.
- How often does a rainwater tank need maintenance?
- Clean leaf eaters and gutter mesh every 6 months. Inspect the inside of the tank for sediment build-up every 2–3 years. Backflow device gets tested annually. Beyond that they're remarkably low-maintenance.