🔍 Key Concepts

• Read the H–Q (head–capacity) curve and identify what "shut‑off" means in terms of pump capacity (flow in GPM). • Understand that shut‑off head is the maximum head the pump can develop when the discharge is closed (zero flow). • Convert feet of head to psi, remembering that 1 psi ≈ 2.31 ft of fresh water and that salt water is slightly heavier (so the ft/psi value is a bit lower).

💭 Think About

• On the H–Q curve, at what flow rate does shut‑off occur, and what is the corresponding total head in feet? • Once you read that head value in feet, how do you convert that to psi, and how will using salt water (heavier than fresh water) change the result slightly? • Compare your calculated psi to the answer choices and decide which one is closest to your result.

✅ Before You Answer

• Make sure you are reading total head (H) from the left vertical axis, not efficiency or BHP from the other axes. • Confirm you are at the correct point on the curve for shut‑off (look at where flow, Q, is zero or where the curve indicates the pump’s maximum head). • Use the correct conversion: for an exam approximation you can use 1 psi ≈ 2.3 ft of water head, then adjust slightly for salt water before matching to the choices.