Wells & water/ CALCULATOR
Estimate how long a tank takes to reach capacity when water is entering and may also be used.
FROM ESTIMATE TO ACTION
Use litres up to the intended working full level, not the overflow level. Starting water must not exceed that capacity. Measure inflow and simultaneous use in L/min under the same operating conditions; a pump’s maximum catalogue flow is not necessarily the flow entering this tank. Do not enter a tank to measure it.
For 1000 L capacity and 200 L initially, 800 L remain. With 20 L/min entering and 5 L/min leaving, net filling is 15 L/min: 800 / 15 = 53.3 min. With no outflow, it takes 40 min. Equal or greater outflow cannot fill a partly empty tank in this model and is rejected. An already-full tank returns zero time only with valid positive net inflow.
Keeping the same 800 L gap and 5 L/min outflow, reducing inflow to 10 L/min gives 160 min, not twice 53.3 min. At 5.1 L/min it takes 8000 min: near-balanced flows make the estimate very sensitive. Pump cycling, pauses, changing demand and falling supply are not simulated. Model separate constant-flow stages with updated starting volumes, or verify a real fill interval; this is not an overflow-control or dry-run-protection design.