The short answer
Turn the water off at the meter, which is usually at the front boundary. Open a tap inside to drain the pressure out of the line. Keep anything electrical clear of the water. Then get in touch. If water is near a switchboard or there is any risk to life, call 000 first.
Do these in order
1. Water off at the meter. The isolation valve is usually at the front boundary, in a box at ground level, often near the fence line. There is a tap or a lever on the house side of the meter. Turn it clockwise until it stops. On some properties it is stiff from years of not being touched, and it may need a firm hand rather than a delicate one.
2. Open a tap inside. Preferably the lowest one in the house. This drains the pressure out of the pipework so the leak slows to a trickle instead of continuing to push water out at mains pressure.
3. Keep electricals clear. Water and switchboards, power points, extension leads and appliances do not mix. If water is running anywhere near a switchboard, or pooling near powered equipment, treat it as an electrical hazard first and a plumbing problem second.
Then get in touch. With the suburb, what has happened, and where the water is coming from if you know.
If water is near a switchboard, or there is any risk to a person, call 000 before you call anyone else.
Find your isolation valve today
This is the useful part of this article, and it takes two minutes when nothing is wrong.
Go to the front boundary, find the water meter, find the tap on the house side of it, and turn it off and back on again. Now you know where it is, you know it turns, and you know how long it takes to walk there.
The difference between a household that knows this and one that does not is roughly twenty minutes of water at full mains pressure, and twenty minutes is the difference between a wet floor and a replaced ceiling.
A valve that is seized is worth having replaced as a small planned job rather than discovering it during an emergency.
What tends to actually burst
Flexible braided hoses under sinks, vanities and behind toilets. These have a finite life, they fail without warning, and they fail at full pressure. They are cheap to replace on a schedule and expensive to replace after the event. If yours are more than about ten years old, or you cannot remember, they are worth looking at.
Connections at the meter and at taps. A tap shearing off at the water meter is a real call-out we have attended in Essendon. The repair itself is not complicated, it is just urgent: water off, make it safe, new meter connection fitted, water back on.
Old pipework at a joint, usually where it has been under strain from high pressure or movement for a long time.
Anything after a long empty period. Pipework that has sat with no flow, then gets pressurised again, is a common time for a weak point to give up.
Prevention that is worth the money
- Get the mains pressure tested. Pressure well above 500 kPa is why a lot of these fittings fail early.
- Replace flexible hoses on age rather than on failure.
- Know where the isolation valve is, and check it turns.
None of those are expensive. All three are cheaper than one flooded floor.