SettingsSettings for this calculationUS
The volume of water to move — a pool, a flooded floor, a tank.
For a flooded room, multiply the floor area by the water depth. For a pool, the pool volume calculator linked below gives this number from the shell dimensions.
The headline flow on the pump's box or plate — measured with no lift and no hose.
Manufacturers rate small pumps at zero head, so this is the most optimistic number the pump will ever produce. The whole point of this calculator is to work out how much of it survives your lift and hose.
The lift at which the pump's flow falls to zero — on the same plate as the rated flow.
Between zero head and this figure, delivery falls roughly in a straight line. A pump with 8 m maximum head asked to lift 6 m has only a quarter of its curve left to work with.
Height from the water surface up to the hose outlet.
Measured to where the water leaves the hose, not to the pump. Draining downhill to a lower discharge point counts as zero — a hose running downhill does not add lift.
Tools needed: Tape measure
The inside bore of the discharge hose — the single most sensitive number here.
Friction rises with nearly the fifth power of shrinking diameter, so halving the bore multiplies friction loss by roughly thirty. A garden hose on a big pump wastes most of what the pump can do.
Total discharge hose length, including the part lying flat.
Every extra length of hose adds friction whether it climbs or not — length and lift are separate costs.
Estimated drain time
10.4 hours
Built on a linearised pump curve and Hazen–Williams hose friction (C = 150). A manufacturer's published curve, where you have one, governs.
- Delivered flow at the operating point
- 21.14 gal/min
- Share of rated flow surviving lift and hose
- 39.88 %
- Friction head in the hose
- 9.13 ft
- Total dynamic head
- 15.63 ft
They open the calculator with your figures already in it
Pump Drain Time Calculator: 10.42 hours — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Hazen–Williams empirical head-loss formula, h_f = 10.67·L·Q^1.852 / (C^1.852·d^4.87), with C = 150 for smooth plastic/rubber hose — standard engineering hydraulics form (SI units)
- Pump performance approximated as a linear curve from rated flow at zero head to zero flow at rated maximum head — the standard first approximation for small utility and submersible pumps; the manufacturer's published curve governs where one exists
Inputs used
- Water volume to remove
- 13210 gal
- Pump rated flow (at zero head)
- 53 gal/min
- Pump maximum head
- 26 ft
- Vertical lift
- 6.5 ft
- Hose inside diameter
- 1 in
- Hose length
- 33 ft
Intermediate steps
- Delivered flow at the operating point
- 21.14 gal/min
- Share of rated flow surviving lift and hose
- 39.88 %
- Friction head in the hose
- 9.13 ft
- Total dynamic head
- 15.63 ft
Confidence note: Built on a linearised pump curve and Hazen–Williams hose friction (C = 150). A manufacturer's published curve, where you have one, governs.
What this calculation does not cover
- The vertical lift is held constant for the whole job and no water is assumed to arrive while the pump runs. In a pool the lift grows as the level drops; in a flooded basement groundwater, rain or a live leak keeps feeding the space. Real time to empty runs longer than this figure, and where inflow matches the delivered flow the level never falls at all.
- Only straight hose length is charged for friction. Fittings, quick-couplers, a strainer or foot valve, a check valve, kinks, a partly closed discharge and any suction-side pipework all add head that is not in this number. Hazen-Williams with C = 150 is an empirical fit for smooth pipe carrying clean water — silt, debris, cold water or a ribbed corrugated hose all move the real loss away from it, and the formula is at its weakest in bores this small.
- The pump is modelled as a straight line between the two figures on its plate. Where you have the manufacturer's published curve, that curve governs. Nothing here checks that the pump can prime at your suction lift, that it will hold prime as the water shallows, or that it is rated to run continuously for the hours reported — most utility pumps also stop drawing well before the floor is dry.
- This is a time estimate, not a decision to empty the pool. It says nothing about hydrostatic uplift on an empty shell, liner shrinkage or collapse, or the groundwater conditions that decide whether a pool can safely be drained at all. Those questions belong to the pool builder and to the shell's own relief arrangements.
- Where the water goes is outside this calculation. Discharging chlorinated, salt or silt-laden water to a storm drain, a watercourse or adjoining land is regulated in most places, and the receiving drain's capacity may be far below the flow reported here. Confirm the disposal route with the local water authority before running the pump.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations2
- Hazen–Williams empirical head-loss formula, h_f = 10.67·L·Q^1.852 / (C^1.852·d^4.87), with C = 150 for smooth plastic/rubber hose — standard engineering hydraulics form (SI units)
- Pump performance approximated as a linear curve from rated flow at zero head to zero flow at rated maximum head — the standard first approximation for small utility and submersible pumps; the manufacturer's published curve governs where one exists
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