New unit drips 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 | Updated 28 Jul 2026

Case summary

Mitsubishi Electric Wall-mounted1 years oldHDBTengah, Singapore

Concern: A faulty new unit was the read, heading for 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. It never collected in the pan or ran 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.

Questions this case answers

New aircon started dripping after its first service: is the unit faulty?

The timing points at the visit rather than the machine. Servicing means taking the drain pan out to clean it, and this one went back sitting a few millimetres forward on its guide rails. Water forming on the coil rolled down the fins and dripped past the pan edge into the housing instead of reaching the outlet.

Water dripping from the front of the indoor unit: where is it coming from?

A front drip points inside the unit, not at the drain pipe. The pipe here was clear and flowed normally when tested, so the fault sat upstream of it. A visible gap ran between the pan edge and the coil housing, and the drip worsened the longer the unit ran because more cooling makes more water.

Do I need a warranty claim for a leak on a unit under a year old?

Have the pan seating checked first. Nothing was replaced on this unit and no claim was filed. The pan slid back onto its rails, pressed flush until the clips engaged, and a thirty-minute cooling cycle plus a pour test confirmed every drop reached the outlet even under higher flow.

Why does the drain pan come out during a service at all?

It has to, so the tray can be cleaned properly. That step is normal work. What matters is whether it goes back seated on its rails with the clips engaged. A few millimetres out of position is enough for water to miss its catch tray entirely, and the gap is invisible once the cover is on.

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