How Much Water Does a Rural Property Need? Check Before You Buy

Water is one of the easiest things to miss on a rural inspection. The tank looks big and it rained last week, so it seems fine. But the real questions are how much you'll use, whether the roof can refill it, and what happens in a long dry summer. You can get a rough answer to all three before you buy.

Water is only one of the things that catch rural buyers out. If you want the full picture, the free rural land checklist builds a list for the whole property from six quick questions.

How much water does a household use?

About 200 litres per person per day across the whole house is a common planning figure in Australia. That covers showers, toilets, laundry and the kitchen. Gardens, animals and visitors all add to it.

For two people that's roughly 146,000 litres a year, and for a family of four it's closer to 290,000. Careful households on tank water often use less than this, but it's a sensible number to plan with until you know your own habits.

How much tank storage is enough?

For a family of four living on tank water alone, 22,000 to 30,000 litres of storage is a common guide. You'll want more if you'll keep animals, water a garden, or live somewhere with long dry summers.

The mistake people make is sizing for an average year. Southern Australia regularly has three or four dry months over summer, so what matters is whether the tanks can carry you through the worst stretch without rain. That's why many rural homes have several large tanks rather than one.

Will the roof actually fill the tanks?

One millimetre of rain on one square metre of roof gives about one litre of water. Multiply the roof area that drains to the tanks by the yearly rainfall, then take off about 20% for losses, and you have a rough yearly catch.

You can usually estimate the roof area from the listing or a satellite map, and the local yearly rainfall from the Bureau of Meteorology. Try it here:

What should you check at the inspection?

Look at every part of the system, from the roof to the tap: the catchment, the tanks, the pump, and any bore or dam.

• Tanks: how many, what size, what they're made of, any leaks, rust or cracks, and whether the lids and inlet screens are intact.
• Roof and gutters: clean, and not painted with old lead-based paint. Check which parts of the roof actually drain to the tanks.
• First-flush diverter: a small device that dumps the dirtiest first rain after a dry spell. Is there one, and does it work?
• Pump: turn on a tap and check the pressure. Ask how old the pump is, and whether there's a backup if the power or the pump fails. If the tanks sit downhill from the house, check the pump is rated to push water that high.
• Filters: is there a filter on the house supply, what type, and when was the cartridge last changed?
• Leaks: walk the hoses, fittings and pipe runs from tank to house. Look for damp patches, green growth or a pump that clicks on when no tap is running.
• Screens on every opening: fine mesh on the inlet and the overflow, and no gaps around pipes where they enter the tank.
• Water level: how full are the tanks now, and has it rained recently? A full tank after a wet month tells you less than you'd think.
• Bore: the bore head and pump, and any paperwork on its depth and yield.
• Dam: the level, any algae, and what it's used for. Stock, garden or firefighting?

What living on tank water has taught me

I live in a house on tank water. These are the things I'd look at first on any property, because they're the ones that bite after you move in.

• Filters matter. A good filter on the house supply makes a real difference to the water you drink. Find out what's fitted and budget for replacement cartridges.
• The pump has to suit the land. On hilly blocks the tanks are often downhill from the house, and a pump that's fine on flat ground will struggle. You want one with enough head height (how high it can push water) for the climb, plus the pressure you want at the tap.
• Pressure switches can be fiddly. Getting the pump to cut in and out at the right pressure takes some tuning. If the pressure's poor or the pump keeps cycling, that's often where the problem is.
• Little leaks add up. A dripping hose or a weeping joint doesn't look like much, but it runs day and night, and on tank water every litre counts.
• Seal up the tank openings. Close off the gaps around inlet pipes and screen every opening. Thirsty climbing animals will find their way in looking for water, and that means a terrible end for the animal and weeks of odd-tasting drinking water for you. I've been through that one, and you don't forget it.

And the upside: rainwater from your own roof doesn't have chlorine or fluoride added, the way town water does, and a lot of people who switch find they prefer the taste.

What should you ask the seller or agent?

Ask how the water has behaved over the years, not just what's there now. The current owners know things a single inspection can't show you.

• Has the property ever run out of water? When, and what did you do?
• How often do you buy water in, and who delivers it?
• When were the tanks last cleaned or inspected?
• Is there a recent water test result I can see?
• Is the bore licensed or registered, and what does it yield?
• Is any water shared with a neighbour, or covered by an easement or agreement?

Questions like these matter for access, wastewater, power and legal use too. The rural land checklist builds you a list like this for the whole property.

Do you need to test the water?

Yes, before you rely on it for drinking. A test checks for bacteria and, depending on the source, heavy metals, nitrates, pesticides and algae toxins.

Roof rainwater is usually the cleanest private supply, but it's still worth testing. Bore water, especially from a shallow bore, often needs disinfecting, and dam water isn't safe to drink without treatment. Your local council or environmental health officer can point you to a testing service.

What happens if the tanks run dry?

You buy water in. Carted water commonly costs around $200 to $600 or more a load in regional Australia, and in a dry spell you can wait days for a delivery.

Before you buy, find out who delivers water locally, what they charge, and whether a truck can actually reach the tanks in wet weather. If the answer is "the current owners buy a few loads every summer", build that into your running costs.

What about bores and dams?

A good bore can supply water year-round, and a dam is useful for stock, gardens and firefighting. But neither is a simple drop-in replacement for clean tank water.

Bores often need a licence, drilling a new one can cost anywhere from about $5,000 to $50,000 or more, and groundwater can be salty, hard or high in iron. Dams lose a lot of water to evaporation in summer, can grow blue-green algae, and dam water should never be drunk untreated. If the property relies on either, ask for the paperwork and test results.

Sources and further reading

• Better Health Channel (Vic Gov): water quality in tanks, bores and dams
• Queensland Health: safe water on rural properties (PDF)
• Agriculture Victoria: managing farm water supplies
• Bureau of Meteorology: rainfall data for your area
• Great Northern Tanks: what size water tank do I need? (a tank seller, useful for sizing figures)
• The Tank Factory: the cost of water cartage (a tank seller)

This is general guidance, not a property, plumbing or health assessment. Water rules and costs vary by state, council and property. Get the water tested and check the details with the relevant people before you rely on them.