Tank to Pump

Hydraulics & Pressure

Water Hammer

Water hammer is the pressure surge that travels back through a line when moving water is stopped or started too suddenly. Closing a valve fast turns the water's momentum into a damaging spike.

A schematic of a pump on the left feeding water through a hose to a valve on the right. When the valve is slammed shut, a tall spike arrow rises at the valve and a shock wave arcs back up the line toward the pump; when the valve is eased closed, the line stays calm with only a faint ripple.

Water hammer · interactive

SPIKE!Slamming the valve shut stops the moving water all at once. Its momentum has nowhere to go, so a pressure shock wave rebounds back up the line — a transient surge that can split hose, pop couplings, and damage fittings.

How do you close the valve?

You closed the valve instantly. The column of moving water cannot stop instantly, so the energy slams into the shut valve and rebounds as a pressure spike racing back toward the pump — water hammer. This is what stresses and damages the line.

The line here carries water at a steady 70psi before the valve moves. Water hammer is a brief transient on top of that, and this app's engine is steady-state — it does not compute the spike, so the surge shown is illustrative, not a gauge reading. The takeaway is the habit: close valves slowly. Follow your SOPs and your apparatus's own limits.

Choose how you close the valve — Slam shut or Ease closed — and watch the line. A slam sends a pressure shock wave rebounding back toward the pump; easing it closed keeps the line calm.

Water in a charged line has momentum. Shut a nozzle or a valve abruptly and that momentum has nowhere to go, so it converts to a sharp pressure wave that can hammer hose, couplings, appliances, and the pump.

The fix is technique, not math: open and close valves and nozzles smoothly. Slow operation lets the flow change gradually and keeps the surge from ever building.

See also