Water service line calculator

How to call the API and what comes back

POST a JSON body with required demand_gpm as the total peak household demand in US gallons per minute, required supply_pressure_psi as the available pressure at the street or curb connection, and required length_ft as the developed service length in feet. Optionally send residual_pressure_psi when you need a different floor than the default of twenty psi at the house end, and material when the run is not copper—accepted values include copper, pex, polyethylene, hdpe, pvc, cpvc, and galvanized, with common aliases such as pe, poly, and steel. Demand, street pressure, and length must be finite and positive within published absolute limits so intermediate powers stay finite on the Worker and in the browser. Residual must be non-negative and strictly less than street pressure; if residual equals or exceeds supply, there is no pressure budget left for friction and the call fails with invalid_input. On success the body echoes rounded demand_gpm, supply_pressure_psi, length_ft, residual_pressure_psi, material, and hazen_williams_c; reports pressure_budget_psi and available_head_ft; publishes exact_diameter_in and recommended_diameter_in with matched_standard; returns head_loss_ft, pressure_drop_psi, residual_at_house_psi, velocity_fps, and adequate; adds unit labels, method, formula, message, and ordered steps for display or regression. Failed validation—missing demand or street pressure or length, non-positive flow or pressure budget, residual not below supply, unknown material, or values outside absolute limits—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item.

Practical tips, limits, and related searches

Survey the trench path for true developed length including rises and detours, not only the straight-line property setback. Prefer copper or approved plastic materials allowed by the water purveyor; do not assume galvanized C-factors for new smooth plastic. Keep velocity in a moderate band for long services—very high feet per second can rattle pipes and accelerate wear even when residual pressure still looks fine on paper. Round-trip checks are easy: recompute available head as pressure budget times two point three one, rebuild exact diameter from the Hazen-Williams inverse, and confirm head loss at the recommended size stays within the budget after the same twelve-decimal rounding used for all numeric fields. When teaching or writing tests, pair a typical fifteen GPM eighty-foot copper case at sixty psi with a long low-pressure run that forces a larger diameter, and include a deliberate residual greater than or equal to supply to prove the invalid_input path. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when you deliberately send residual above street pressure to verify error handling.