Tank level monitoring

Sensor types

Internal probes are cheap but foul, especially in grey/black tanks. External capacitive strips avoid contact but need compatible tank walls. Pressure sensors can be accurate but require calibration and stable installation.

Calibration

Calibrate empty and known volumes on level ground. Tank shape makes height non-linear: half-height may not be half-volume. Verify alarm/reserve points by measured fill.

Simple works

A translucent sight section, visual tank, flow meter or days-since-fill can be more useful than a false percentage. For fresh water, know the pump outlet's unusable reserve.

Trouble

Erratic readings usually mean fouling, wiring/ground issues, wrong calibration, tank movement or incompatible sensor placement. Never drill a potable tank without the tank maker's approved fitting method.

Build rule

If you cannot reach it, isolate it, drain it and explain its pressure/temperature or water-quality job, it is not ready to hide behind a wall.

CHAPTER CHECK

• I can explain the purpose and failure mode of each item in this chapter. • I know which manufacturer limit or water-quality claim controls my choice. • I added the valve, access, drain, measurement or maintenance task to my drawing/checklist.