Flowmeters

A flowmeter is the only way to know what your pool is actually circulating. Pump nameplates state design flow, not real flow, and the real number depends on filter condition, valve positions, pipe runs and how far the pump has drifted from new. On commercial pools a direct reading flowmeter is usually a code requirement, and on any pool it is the difference between managing turnover and guessing at it.

Sizing and material

Match the meter to your pipe size and material, and confirm your expected flow falls comfortably inside the meter range rather than at either extreme.

• PVC meters from 1 inch through 8 inch, covering 10 GPM up to 1900 GPM.
• Copper meters in 1-1/2, 2, 3 and 4 inch for copper plumbed systems.

A meter reading near the very bottom of its scale is hard to read accurately, so choose the range your system actually operates in rather than the widest one available.

Installation matters more than people expect

Flowmeters need straight, undisturbed pipe to read correctly. Allow roughly ten pipe diameters of straight run upstream and five downstream, away from elbows, tees and valves. Installing one immediately after a 90 degree elbow produces turbulence at the sensor and a reading you cannot trust, which is the most common flowmeter complaint and it is always an installation issue.

What it tells you

Compare actual GPM against the turnover your pool volume and code require. A falling reading over time points to a dirty filter, a closing valve or a failing impeller, which makes the flowmeter one of the cheapest diagnostic tools on the pad.