Using dam water: what it suits, and what to keep it away from
A dam is open to animals, runoff and algae. That makes it handy for stock and the garden, and a poor bet for the kitchen tap.
Dam water is untreated surface water. It is fine for many jobs outside the house, such as watering paddocks or fighting a fire. It is a poor choice for drinking, and you should not plumb it into your home without proper treatment and a licensed plumber.
Start from one fact: a dam collects whatever runs into it. That includes soil, manure, fertiliser, leaves and the droppings of every animal that visits.
What is dam water good for?
- Stock and garden watering. Check what your plants and animals tolerate, since salty or algae-rich water can harm both.
- Fire fighting supply. A full dam is a useful reserve.
- Washing machinery and hard surfaces. Anything that does not touch food or skin for long.
Why is dam water risky to drink?
Dam water can carry bacteria, parasites, blue-green algae and agricultural chemicals. It can look clear and still be unsafe. It can also be murky and perfectly harmless, which is why your eyes are no guide.
Boiling, a jug filter or a carbon cartridge will not turn it into drinking water you can trust. A carbon filter improves taste and does little about microbes or dissolved chemicals.
What would it take to treat it?
A proper setup usually means several stages: a way to remove silt, then filtration, then disinfection. The right combination depends on what a laboratory finds in your water, and that changes with the season and the weather. A system designed without a test is a guess.
Read about whole-house filters to see what each stage does and what it leaves alone. Then get the test first and the design second.
Dam water versus tank and bore water
Rain collected from a roof starts cleaner than runoff from the ground, which is one reason tank water is easier to manage. Bore water comes from underground and has its own problems, mostly dissolved minerals. A dam is the most exposed of the three.
If you have a choice, do not make a dam your first pick for anything that reaches a drinking tap.
Keep it out of the house plumbing
Using dam water for the toilet or the laundry is possible, but it needs a separate, correctly labelled system and the right protection against backflow. Never join it to the drinking supply. The basics of why are in our page on non-potable water.
Algae in a dam can bloom in warm weather. If the water turns green, scummy or smells bad, keep stock, pets and people away and ask your local water or health authority for advice.
Dam water jobs: what suits it and what does not
Treat dam water as untreated surface water and match the job to the risk.
| Use | Suitable? | Condition |
|---|---|---|
| Stock watering | Often | Check what your animals tolerate, since salty or algae-rich water can harm them |
| Garden and paddocks | Often | Check your plants too, for the same reason |
| Fire fighting reserve | Yes | A full dam is a useful supply |
| Washing machinery and hard surfaces | Yes | Only where it does not touch food or skin for long |
| Toilet or laundry | Only with a separate system | Labelled, with backflow protection, fitted by a licensed plumber |
| Drinking or cooking | No | Not as it comes. Boiling or a jug filter does not make it trustworthy |
If the dam turns green, scummy or smelly, keep stock, pets and people away and ask your local water or health authority. The non-potable water guide explains why indoor uses need their own plumbing.
Before you connect dam water to anything: the order to follow
The common mistake is buying equipment first. Do it in this order instead, so the design fits the water you actually have.
- Decide what the water is for. Stock, garden and fire fighting need far less than a house supply.
- Collect a sample the way the laboratory tells you. A badly taken sample gives a wrong answer that looks official.
- Use an accredited NATA laboratory. Ask what it recommends testing for, given your land and your intended use.
- Test again after weather changes. The result shifts with the season and the rain, so one pass is not permanent.
- Design the treatment from the result. It usually means silt removal, then filtration, then disinfection. A system designed without a test is a guess.
- Hire a licensed plumber for the connection. Pumping to the house, fitting treatment or joining indoor plumbing is licensed work, and never to the drinking supply.
Our whole-house filter guide shows what each treatment stage does and what it leaves alone.
Frequently asked questions
Is dam water safe to drink?
Not as it comes. Dam water is untreated surface water and can carry bacteria, parasites, algae and chemicals. Only an accredited NATA laboratory test, followed by proper treatment, can address that.
Will boiling make dam water safe?
Boiling does not deal with every risk, such as dissolved chemicals or algae toxins. Do not rely on it. Test the water through an accredited laboratory.
Can I use dam water in the house?
Only through a separate, labelled non-potable system fitted by a licensed plumber, with backflow protection. It must never be joined to the drinking supply.
What is dam water good for?
It suits stock and garden watering, fire fighting supply and washing machinery, as long as the water quality suits your plants and animals.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Sydney Water. Water supply, wastewater and stormwater services