CO Testing After Water Heater Install

Purpose

Mandatory CO testing procedure after every water heater installation — this is a safety-critical step that must never be skipped.

When to Use

• After EVERY gas water heater installation (tank or tankless)
• After EVERY gas water heater repair that involved venting, gas connections, or burner work
• This applies to both service technicians and install crews

Procedure

Required Equipment

• Klein ET110 Carbon Monoxide Meter (or equivalent approved detector)
• Meter must be calibrated and charged

Testing Sequence

Allow the water heater to run for at least 10 minutes before testing — the system needs to reach operating temperature

Test ambient CO in the room — record the reading (should be 0-5 PPM)

Test at the draft hood (tank) or exhaust vent (tankless) — record reading

Test at the flue pipe connections — record reading

Verify draft direction using a smoke pencil or match: smoke should pull toward the vent, not push out into the room

Check for backdrafting — especially if the water heater shares a flue with other appliances

If a tankless unit, test at the exterior exhaust termination

Acceptable Readings

• Ambient room: 0-9 PPM is normal
• At draft hood/vent: 0-9 PPM after warm-up
• Any reading above 9 PPM requires investigation
• Any reading above 35 PPM requires immediate action per CO Detection & Response SOP

Open Exhaust Vent Check

While testing, visually inspect for open or uncapped exhaust vents from previously removed appliances

Open vents create a backdraft pathway — address per Open Exhaust Vent Handling SOP

If an open vent is found, cap it before completing the installation (at minimum a temporary cap)

Documentation

Record all CO readings in ServiceTitan job notes

Photo the CO meter displaying the readings

Photo the completed vent connections

If any readings were elevated and corrected, document what was found and fixed

Pass/Fail Criteria

• PASS: All readings under 9 PPM, draft pulling correctly, no backdrafting, no open exhaust vents
• FAIL: Any reading above 9 PPM, improper draft, backdrafting detected, open exhaust vents unaddressed
• A failed CO test means the job is NOT complete — do not leave until resolved

Important Notes

• This test is mandatory — skipping it is a safety violation and a liability risk
• If you cannot get readings below 9 PPM after troubleshooting, call your supervisor
• Open exhaust vents are a common CO source that was previously inconsistently addressed — check every time
• CO is odorless and colorless — your meter is the only way to detect it
• This SOP addresses a critical missing procedure that was identified in the safety audit

Related SOPs

• Carbon Monoxide (CO) Detection & Response — full CO emergency protocol
• Open Exhaust Vent Handling Procedures — addressing open vents
• Water Heater Installation (40/50 gal) — full installation procedure
• Tankless Water Heater Installation — tankless installation procedure