Pump curve
System curve
H = Hstat + k·Q²
Awaiting Valid Duty Parameters
Adjust the parameters on the left to compute live hydraulic values, ranges, and sizing verdicts.
Running off your pump’s best efficiency point?
Off-curve operation wastes energy and kills seals. Our engineers plot your actual system curve and re-rate pumps to the real duty.
Reading the operating point
The two curves
A pump curve says what the pump can deliver: head falls as flow rises. The system curve says what the system demands: head rises with the square of flow because friction grows with velocity — H = static head + k·Q². The pump runs where the two cross, and nowhere else. Change the static head or the pipe size and the operating point slides along the pump curve.
Two points on the pump curve are enough for a straight-line fit in this tool; real curves are curved, so use points near the expected duty. The friction coefficient k comes from the pipe friction tools — roughly head loss at 1 m³/h.
Why the operating point matters
Every selection decision hangs on the operating point. If it sits far right of the best efficiency point, the pump may overload the motor and cavitate; far left, the pump wastes energy on throttling and recirculates internally. The affinity laws show how a speed change moves the pump curve, and this tool shows where it lands on the system curve.
Using it with the other tools
Build the system curve from the head-loss tool (friction at several flows), enter static head from your layout, and let this tool find the duty. Then size the motor with the motor calculator and check NPSH with the NPSH tool at the found flow. Teflow’s engineers run the same sequence on every retrofit — call +91 98251 62709 for a curve review.
Technical & Operational FAQs
Q1.What is the system curve?
The system curve is the head the piping demands at each flow: static head (fixed by elevation) plus friction loss, which grows with the square of flow. H = Hstat + k·Q². The pump operates where this curve crosses the pump curve.
Q2.How do I find the operating point?
Plot the pump curve (head vs flow from the datasheet) and the system curve, and read where they cross. This tool fits the pump curve through two entered points and solves the intersection with the system curve automatically.
Q3.What if my pump runs off the curve?
Off-curve operation usually means the system changed: a new static head, a partially closed valve, fouled pipes or a worn impeller. Plot both curves to see the shift, then re-rate, trim or replace. Running far right overloads the motor; far left wastes energy.
Q4.How do I get the friction coefficient k?
k equals the friction head at exactly 1 m³/h (since H = k·1²). Measure or compute friction at any flow with the head-loss tool and divide by Q² to get k, then enter it here.
Q5.Why is my pump delivering less than rated?
Three common reasons: the system curve crosses the pump curve at a lower flow than the rated point, the impeller is worn or trimmed, or suction problems (air, NPSH) limit the duty. Plot the operating point with this tool to separate curve-shape issues from suction issues.
Related Engineering Tools
Pipe Head Loss Calculator
Chemical Pump Sizing Calculator
Affinity Laws Calculator
NPSH Available Calculator
Pump Repair Service
Pump Consultancy
Need a custom hydraulic audit or specific duty curve verification? Call +91 98251 62709 or Request a Detailed Engineering Quote.