W-403: Low basin level

Q: How do I check a W-403 fault?

1. Check make-up valve and float 2. Inspect basin for leaks 3. Review blowdown rate Safety: Lock out fans before entry; use respiratory protection near drift.

Probable causes

Make-up valve fault
Excess blowdown
Leak

Step-by-step checks

Check make-up valve and float
Inspect basin for leaks
Review blowdown rate

Safety: Lock out fans before entry; use respiratory protection near drift.

Sample code — verify with the OEM manual for your exact model.

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Frequently asked questions

What does W-403 mean on a Cooling Tower?

W-403 usually indicates: Low basin level. Confirm the meaning in the manufacturer's manual for your model.

What causes W-403?

Make-up valve fault; Excess blowdown; Leak.

How do I check a W-403 fault?

Work through the numbered checks above in order, recording readings as you go. Lock out fans before entry; use respiratory protection near drift.

Other Cooling Tower codes

Disclaimer: Fault code information is guidance only. Codes and meanings vary between manufacturers and models — always follow the manufacturer's manual and your site's safety procedures, and use qualified personnel for electrical, pressure, refrigerant and combustion work.