Wells & water/ CALCULATOR
Calculate how many litres a straight pipe run holds from its internal diameter and length.
FROM ESTIMATE TO ACTION
Enter internal diameter in mm and pipe length in m: 25 mm and 30 m, not 0.025 in the diameter field. DN, outside diameter and actual bore are not interchangeable. Use product dimensions or an existing safe measurement; do not open a pressurised pipe to obtain a number. Calculate each constant-bore section separately, including branches only once.
A full 25 mm bore over 30 m contains 14.7 L, or 0.491 L/m. A mixed route with 10 m at 20 mm and 20 m at 25 mm contains about 3.14 + 9.82 = 12.96 L. Sum unrounded section results before final rounding. Volume grows with diameter squared: a +10% diameter change gives +21% volume at the same length, not +10%.
This is geometric capacity for a full circular pipe, not an estimate of water already present in a partly empty line. Fittings, vessels and other cavities need separate known volumes without double counting. The result does not establish adequate flow or pressure, drinking-water safety, disinfection requirements or the flushing volume required. Hot-water waiting also depends on flow and heat losses; do not treat these litres alone as a measured waiting time.