Office Cassette Leaked After Service: Pump Cover Misaligned

A leak follows a service and the pump is the obvious suspect. What the work had to take off and put back is the shorter list.

By Team Snowflake | Updated 24 Aug 2026

Teaching case based on recurring Snowflake service patterns; identifying details are combined.

How this presents

Water beneath a ceiling unit some time after servicing, with the pump running strongly whenever it is called on. Nothing obstructs the run at any point. The pump empties the chamber when it is tested by hand.

Setup: Mitsubishi Electric Cassette4-6 yearsOfficeStraits View
Misread as: Pump capacity that can no longer keep up, needing a replacement on ceiling equipment.
Check first: Whether water escapes as the level rises, rather than while the pump is running

What else produces this

A pump that empties its chamber on demand is doing everything asked of it, so whatever escapes is leaving before the pump gets to it. That points at the chamber rather than the pump, and the chamber is closed by its cover. A cover sitting slightly out of alignment leaves a path along one edge. Water takes that path as the level rises, rather than waiting to be lifted away.

A pump emptying the chamber on demand confirms it is doing everything asked of it.
A clear drain line rules out anything obstructing the water once the pump has lifted it.
A cover sitting out of alignment leaves a path along one edge of the chamber.
Water escaping as the level rises, rather than while the pump runs, fits that path exactly.

Why it happens

A pump chamber holds water until there is enough to lift, and its cover closes that volume. Refitted slightly out of true, the cover no longer meets its seat all the way round, so a small gap runs along one edge. Water reaching that level goes out through it instead of waiting for the pump. Everything else works perfectly, and the pump never gets the chance to do its job.

What resolution involves

Realigning the cover so it meets its seat evenly the whole way round is the entire repair, and nothing is replaced. Naming what a cover does is the useful part here. On a pump chamber it is part of the vessel rather than a lid on top of one, so refitting it squarely matters as much as anything else on the unit.

How to tell it worked

The chamber filled and watched at the level where water was escaping, rather than while the pump runs. The escape happens before the pump is called, so testing during a pump cycle misses it completely.

Before you approve a quote

On a pump chamber the cover is part of the vessel

A pump chamber holds water before lifting it. Its cover closes that volume, and has to seat evenly.
A pump that empties on demand is working. What escapes is leaving before the pump is ever called.
Refit the cover squarely. Out of true by a little, it leaves a path along one edge of the seat.

Questions this case answers

Ceiling cassette started dripping over desks the same day it was cleaned. Where do we look?

At the pump chamber cover. The cover closes the chamber and has to seat evenly; refitted slightly out of alignment, it leaves a path along one edge for water to escape.

Does water over the desks mean the ceiling pipe has failed?

No. Nothing obstructed the run in this case; water was escaping from the pump chamber because its cover had been refitted out of alignment.

Can this be repaired without opening the ceiling?

Yes. The whole repair is realigning the chamber cover so it meets its seat evenly, and nothing is replaced.

Why does the timing of the first drip matter so much?

Because water escapes as the level rises, before the pump is ever called. A drip that starts while the pump is not running points at the chamber cover rather than at a pump or pipe failure.

Ready to get started?

Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.

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