The Burst Pipe Water Loss Timer estimates how fast water leaves a broken supply pipe and how much escapes before the main is closed. Choose the pipe size, the kind of break, your water pressure, your supply limit, the minutes to shut-off and the floor area. It uses an orifice-flow formula capped by the supply limit, and shows litres per minute, the total, litres per hour and depth.
- Flow through the break is Q = 0.62 × A × √(2ΔP/ρ), then capped at the most your house supply can deliver.
- At the defaults, a split ½-inch pipe at 60 psi is supply-limited at 45 L a minute: 675 L in 15 minutes and 2,700 L an hour.
- A 1 mm pinhole at 60 psi passes about 0.8 L a minute: about 13 L in 15 minutes and 50 L an hour.
- A 1 × 25 mm crack at 60 psi passes about 27 L a minute, about 401 L in 15 minutes.
- The depth figure assumes water spreads evenly, which it rarely does; it runs to low spots and into walls.
Burst Pipe Water Loss Timer
01 /What does the Burst Pipe Water Loss Timer show?
It turns the minutes before a shut-off into litres. A burst pipe is an emergency measured in time: every minute spent looking for a valve, a flashlight or a phone number adds water to the floor, the walls and the room below. The timer makes that concrete, so you can see what a pinhole, a crack or a full split releases at your water pressure, and how much those extra minutes cost.
It updates as you change any input; there is no button to press. The result shows the flow in litres a minute, the total over your chosen minutes, the litres an hour with a bathtub comparison, and a drawing of how deep that water would stand if it spread evenly over the floor area you entered, against a 50 mm box.
02 /What inputs does the tool use?
| Input | Options or range | Default |
|---|---|---|
| Pipe size | ½ inch, ¾ inch or 1 inch (bores of 13, 19 or 25 mm) | ½ inch |
| What broke | Pinhole (about 1 mm); crack (about 1 × 25 mm); split open (full bore); fitting blown off (full bore) | Split open |
| Water pressure | 10 to 150 psi | 60 psi |
| Most your house supply can deliver | 5 to 200 L/min | 45 L/min |
| Minutes until the water is shut off | Slider, 1 to 120 minutes | 15 minutes |
| Floor area the water spreads over | 1 to 500 m² | 12 m² |
Pipe size only matters for the two full-bore breaks, because a pinhole and a crack have fixed opening sizes in the model. A split and a blown-off fitting are both treated as the whole bore of the pipe being open.
03 /How does the tool calculate the flow?
It treats the break as an orifice and applies the standard orifice-flow equation, then caps the answer at your supply limit. The steps are:
- Area of the break
Pinhole: a circle 1 mm across, π/4 × (0.001 m)², about 7.85 × 10⁻⁷ m². Crack: a slot 1 mm by 25 mm, 2.5 × 10⁻⁵ m². Full bore: π/4 × d², using 13, 19 or 25 mm.
- Pressure in pascals
ΔP = psi × 6,894.76. At 60 psi that is about 413,686 Pa.
- Orifice flow
Q = 0.62 × A × √(2ΔP/ρ), with water density ρ = 1,000 kg/m³ and a discharge coefficient of 0.62, converted from cubic metres a second to litres a minute.
- Supply cap
The flow used is the smaller of Q and the supply limit you entered. The result says which one governs: the size of the break or your supply.
- Totals
Litres in your chosen minutes = flow × minutes. Litres an hour = flow × 60, also shown as bathtubs of 150 L.
- Depth
Depth in mm = total litres ÷ floor area in m². It is drawn against a 50 mm box, which fills completely at 50 mm or more.
Worked through for a 1 mm pinhole at 60 psi: √(2 × 413,686 ÷ 1,000) is about 28.8 m/s, so Q = 0.62 × 7.85 × 10⁻⁷ × 28.8 ≈ 1.40 × 10⁻⁵ m³/s, or about 0.84 L a minute. That is well under the 45 L cap, so the break governs.
04 /What do the worked examples show?
They show that small breaks are limited by their size and big ones by the house supply. These results use the default 60 psi, 45 L a minute cap, 15 minutes and 12 m².
| Break | Uncapped orifice flow | Flow used | In 15 minutes | Per hour | Depth over 12 m² |
|---|---|---|---|---|---|
| 1 mm pinhole | About 0.8 L/min | About 0.8 L/min (break-limited) | About 13 L | About 50 L (0.3 bathtubs) | About 1.1 mm |
| 1 × 25 mm crack | About 27 L/min | About 27 L/min (break-limited) | About 401 L | About 1,605 L (10.7 bathtubs) | About 33 mm |
| ½-inch split, full bore | About 142 L/min | 45 L/min (supply-limited) | 675 L | 2,700 L (18.0 bathtubs) | About 56 mm |
| ¾-inch split, full bore | About 303 L/min | 45 L/min (supply-limited) | 675 L | 2,700 L | About 56 mm |
| 1-inch split, full bore | About 525 L/min | 45 L/min (supply-limited) | 675 L | 2,700 L | About 56 mm |
Once a break is large enough, the pipe size stops mattering and the supply cap sets the result. Change the minutes instead: the same ½-inch split releases about 225 L in 5 minutes and 1,350 L in 30 minutes.
05 /How does water pressure change the result?
Flow through an opening rises with the square root of pressure, so doubling the pressure raises flow by about 41%, not 100%. For breaks that are already supply-limited, pressure changes nothing in the tool, because the cap applies first.
| Break | 40 psi | 60 psi | 80 psi |
|---|---|---|---|
| 1 mm pinhole | About 0.7 L/min, 10 L | About 0.8 L/min, 13 L | About 1.0 L/min, 15 L |
| 1 × 25 mm crack | About 22 L/min, 328 L | About 27 L/min, 401 L | About 31 L/min, 463 L |
Household pressure varies by municipality, elevation and whether the house has a pressure-reducing valve. If you do not know yours, a plumber can measure it with a gauge on a hose bib or laundry tap. High pressure is also one of the causes worth checking after a burst; see preventing another burst pipe.
06 /What is the supply limit, and what should you enter?
It is the most water your service line, meter and plumbing can deliver to an open break, and it is often what governs a real burst. The default of 45 L a minute is a representative planning value, not a measurement of your home. A larger service line, a larger meter or higher pressure raises it; a long, narrow or corroded service lowers it.
- If a plumber has measured your available flow, enter that.
- A bucket test at the fastest tap, fully open, gives a lower bound only; a full-bore break can draw more than a single tap.
- Older galvanized services often deliver much less than their size suggests because of internal corrosion.
- If you are not sure, keep the default and try higher and lower values to see the range.
07 /What are the limits of this estimate?
It is an orifice-flow estimate with a single discharge coefficient of 0.62 and a cap you enter; it is not a hydraulic model of your plumbing. Real breaks have jagged edges, change shape as they tear, and sit on pipes whose pressure drops as flow rises. Water never spreads evenly: it runs to the lowest point, under baseboards and flooring, into wall cavities and through ceilings, so a modest average depth can mean a soaked corner and a ruined ceiling below.
It also counts only water released before the shut-off. After the valve closes, the water still in the pipes drains out through the break unless you open a lower tap, as the first-hour checklist explains.
08 /How should you use the result?
Use it three ways: to justify learning where your valve is, to understand the size of the drying job, and to describe a loss clearly. The fastest win is the first one. Five minutes saved on a full split is about 225 litres that never reach the floor.
- Before anything happens: find and tag your main shut-off using the main shut-off guide, then run the timer with the minutes it would take you now.
- After a burst: estimate how much water escaped, and use that with the drying guide to judge whether you need professional drying; Health Canada ties a lower mould risk to drying a house within 48 hours.
- For the claim: a realistic volume helps explain the extent of damage; keep your photos and the plumber's report as the main evidence, as set out in documenting the claim.
To see how your pipe should be repaired once the water is off, try the Burst Pipe Repair Matcher. Costs that follow from the litres are in burst pipe repair cost.
FAQQuestions people ask
How much water comes out of a burst pipe per minute?
A fully split pipe can release as much as the house supply delivers; at the tool's default cap that is 45 L a minute. A 1 mm pinhole at 60 psi passes about 0.8 L a minute.
How much water can a burst pipe release in an hour?
At a 45 L a minute supply limit, about 2,700 litres, or roughly 18 bathtubs of 150 L. A 1 × 25 mm crack at 60 psi releases about 1,605 litres an hour.
Why does pipe size not change the result for a split pipe?
Because even a ½-inch full-bore break can pass more water than the default supply limit. Once the break is bigger than the supply, the supply sets the flow.
What discharge coefficient does the tool use?
0.62, a common value for sharp-edged openings. Real breaks vary, so treat the output as an estimate.
Is the water depth in the tool accurate?
It is an average over the area you enter. Real water runs to low spots and into walls, so some areas will be much wetter than the average.