New unit dripping after first service: drain pan not reseated
A leak from a new unit right after its first service points the finger at a faulty install or a bad unit. But servicing means taking the drain pan out to clean it. How that pan goes back decides whether drain water stays on track.
By Team Snowflake | Reviewed 10 Mar 2026
Case summary
Mitsubishi Electric Wall-mounted1 years oldHDBTengah, Singapore
- Concern
- The owner feared the new unit was faulty and would need a warranty claim or a full replacement.
- Found
- Drain pan was not reseated flush against the evaporator coil housing after servicing. A gap was left where drain water dripped past the pan
- Key check
- Checked the drain pan seating and alignment against the coil housing before investigating drain pipe or refrigerant issues
- Result
- The dripping stopped completely. The unit ran through a full cycle with all the drain water reaching the outlet as it should.
What we were told
The bedroom aircon started dripping water right after its first service. It had been completely dry before. The unit was under a year old, so the owner asked whether it might be faulty.
What we checked
A leak that starts right after a service on a dry unit points back to the service visit. We opened the indoor unit and checked the drain pan seating first, before looking at the drain pipe or the gas system. We removed the front cover and checked the pan position against the coil housing. We also poured water into the pan outlet to test the drain pipe and rule out a blockage.
Water was dripping from the front edge of the indoor unit, not from the drain outlet.
The drain pipe was clear and flowed normally when tested.
The drain pan sat slightly forward of the coil housing.
A visible gap between the pan edge and the housing let drain water slip past the pan.
What we found
At the previous service, the drain pan was taken out for cleaning. This is a normal step. When it went back, it sat a few millimetres forward of its correct spot on the guide rails. With that gap, water forming on the coil rolled down the fins, reached the bottom edge, and dripped past the pan into the housing instead of collecting in the pan and running to the drain outlet. The drip got worse the longer the unit ran, because more cooling means more water. The unit itself worked perfectly. The water was simply missing its catch tray.
What fixed it
We slid the drain pan back onto its guide rails, pressing it flush against the coil housing until the clips engaged. We then ran a full cooling cycle for thirty minutes and watched the water the whole time to confirm it reached the drain outlet with no drips past the pan. A pour test, sending extra water onto the coil, confirmed the path held under higher flow. No parts were needed and no warranty claim was required.
Outcome
The dripping stopped completely. The unit ran through a full cycle with all the drain water reaching the outlet as it should.
What this case teaches us
A leak right after a service usually traces back to the service
- When a unit is dry one day and dripping the next, the recent service visit is the first suspect, not the unit.
- The drain pan comes out during cleaning. If it goes back even a few millimetres off its rails, water drips past it into the housing.
- A new unit leaking after its first service rarely means a warranty claim. Have the pan seating checked first.
Related reading
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