Garden Garden hose pressure loss calculator
Every foot of hose costs you pressure to friction, and the effect is dramatically non-linear: halving the diameter costs far more than doubling the length. A 100 foot ½ inch hose can lose most of your usable pressure before the water reaches the sprinkler.
How this is calculated
Hazen-Williams friction loss with C=150 for smooth hose: head loss in feet per 100 ft = 0.2083 × (100 ÷ C)^1.852 × GPM^1.852 ÷ diameter^4.8655, converted at 0.433 psi per foot. Elevation adds a further 0.433 psi per foot of rise.
Source: Hazen-Williams equation, the standard method for friction loss in water pipe; 0.433 psi per foot is the density of water
Worth knowing: This models the hose only. Quick-connect fittings, a kinked coil, a partly-closed tap and an inline filter each add losses of their own, so treat the result as a best case. The practical takeaway rarely changes: if the far end is weak, go up a diameter before you go looking for a better sprinkler.
Common questions
Does hose diameter really matter that much?
Enormously. Friction loss scales with diameter to roughly the fifth power, so going from 1/2 inch to 5/8 inch cuts losses by more than half at the same flow. If you run long hoses to a sprinkler, diameter is the single most effective thing to change.
Is a longer hose or a narrower hose worse?
Narrower, by a wide margin. Doubling length doubles the loss; halving diameter multiplies it many times over. Two 50 foot 5/8 inch hoses joined will outperform one 100 foot 1/2 inch hose comfortably.
Why does my sprinkler work at the tap but not at the end of the hose?
Because the sprinkler is designed around pressure at the head, not at the tap. Most oscillating and impact sprinklers want 30-50 psi to throw properly. Lose 25 psi in the hose and the same sprinkler that soaked the driveway now waters a small circle.
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