Choose pipe size that matches your pump flow. Factor lift, distance, and common garden fittings. Export results as CSV or PDF for records quickly.
| Scenario | Flow | Lift | Run | Fittings | Target limits | Typical outcome |
|---|---|---|---|---|---|---|
| Raised bed drainage | 35 GPM | 8 ft | 40 ft | 4×90°, check, ball | V ≤ 8 ft/s, HL ≤ 8/100 | Often 1-1/2" to 2" |
| Long garden discharge | 30 GPM | 10 ft | 120 ft | 6×90°, check, gate | V ≤ 7 ft/s, HL ≤ 6/100 | Often 2" to 2-1/2" |
| Short outlet to swale | 25 GPM | 6 ft | 20 ft | 2×90°, no check | V ≤ 8 ft/s, HL ≤ 10/100 | Often 1-1/4" to 1-1/2" |
Start with the pump’s expected flow at real head, not the label rating. Garden sump setups deliver 20–60 GPM. This calculator treats your entered flow as the design point and checks candidate pipe sizes against velocity and friction targets. Keeping discharge velocity moderate reduces noise, water hammer, and check‑valve wear. A common goal is 6–8 ft/s for short runs, and lower for long routes.
Static lift is the vertical rise from the sump waterline to the discharge outlet. Total dynamic head (TDH) adds friction loss in straight pipe and minor losses from fittings. The report shows TDH and TDH plus a safety factor to represent aging, biofilm, and small routing changes. Higher TDH usually lowers delivered flow and can increase cycling frequency.
Friction loss is estimated with the Hazen–Williams method using a C factor. Smooth plastic generally uses higher C values than metal, producing lower calculated loss for the same diameter. The tool also displays friction loss per 100 ft (or per 100 m) so layouts compare with clarity. When the headloss limit is tight, the recommended size often steps up one nominal diameter.
Elbows, a check valve, and shutoff valves add minor loss through K values summed into one total. This matters most when the run is short and fittings dominate the system. Fewer sharp turns, long‑radius elbows, and low‑loss valves can reduce TDH without changing diameter. Enter fitting counts that match your plan, including adapters that create extra turns.
The sizing table shows which diameters meet your velocity and headloss limits, helping you choose the smallest pipe that preserves pump performance. Confirm internal diameter for your pipe standard before purchase, especially when changing schedules or materials. After installation, verify discharge and avoid short‑cycling; if it occurs, reduce restrictions or increase diameter where feasible.
Use your pump’s real flow and route details, then compare the table. Many installs land between 1-1/2" and 2", but long runs or higher flow can push larger sizes.
A check valve adds minor loss and can raise total dynamic head. Higher head usually reduces flow on the pump curve, so a slightly larger discharge pipe can help recover capacity.
For quiet operation, aim near 6–8 ft/s (about 1.8–2.4 m/s). Choose lower limits for long piping, flexible hose sections, or where vibration and noise are concerns.
It is widely used for water flow in full pipes and provides a practical estimate. Results depend on actual internal diameter, fittings, and pipe condition, so treat the output as sizing guidance.
Use a conservative C factor and include extra length allowance for roughness and bends. If possible, replace short hose sections with smooth pipe to lower losses and improve reliability.
Increase the allowable headloss, reduce fittings, shorten the run, or step up diameter. If head is still high, verify pump selection against the required total dynamic head.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.