Vertical pressure tank connected to a water pump outdoors

Constant-pressure well drive shows a fault or pressure surges

Read the code first; it tells you whether the problem is supply power, settings, the transducer or the pump/motor. Surging at low flow is almost always tank precharge. Use the drive maker's code list; the examples here are Franklin SubDrive/MonoDrive Connect.

Cross-checked ~60 min advancedBrands: Franklin Electric, Grundfos, Pentair, Goulds, Others

Before you start

230 V with stored DC energy: lock out and wait the discharge time printed on the drive before opening
Live input-voltage checks are caution work

Diagnostic steps

Unlock all 7 steps with expected values

Full library + AI assistant for $34.90, one time.

Get lifetime access

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

More sump & well pumps guides

Guide · Sump / Well Pump

Well pressure switch chattering or clicking rapidly

Chatter happens when the switch sees pressure bouncing around its set point. The usual causes are a plugged sensing port or nipple, a waterlogged or low-precharge tank, a switch mounted far from the tank, worn contacts or a differential set too narrow. Chatter burns contacts fast and stresses the motor, so fix it the same day.

8 steps ~45 minmoderate

Guide · Sump / Well Pump

Jet pump loses prime or runs without building pressure

A jet pump only works when its housing and suction line are full of water. Lost prime almost always traces to an air leak on the suction side, a leaking foot valve or check valve, a clogged foot-valve screen, or a well that has drawn down. Fix the cause, then re-prime; repeated priming alone just burns pumps.

7 steps ~60 minmoderate

Guide · Sump / Well Pump

Well pump hums, won't start or trips overload: control box test (3-wire)

On a 3-wire submersible, the start capacitor and relay in the control box are the most common surface failures and can be tested with a meter. First confirm power through the pressure switch, then test the box. If the box is good or the system is 2-wire, the problem is down the well and goes to a well contractor.

8 steps ~60 minadvanced