Flat Leaked After Servicing: Drain Refitted with Poor Fall

A flat leaks after servicing and years of deposit are blamed. Whether the line is choked or was reconnected slightly wrong.

By Team Snowflake | Updated 24 Aug 2026

How this presents

Escaping water at a unit within a week of a service, on a line that has drained correctly for years. Nothing is blocking the pipe at any point along it. The drain was disconnected and reconnected while the work was done.

Setup: Gree Wall-mounted4-6 yearsHDBYishun
Misread as: Deposit that has accumulated over the years, meaning the line has to be cleared or replaced.
Check first: Whether the reconnected run still carries water all the way to the outlet

What else produces this

A line that drained for years and stopped straight after a service has had its position changed rather than its contents. Fall is what makes a drain work, and it is set by exactly where the pipe sits. Reconnecting at a slightly different height is enough to lose it. The check is to send water down and watch, because a gradient this marginal is neither visible nor measurable by eye.

Years of correct drainage before the service rules out any long-standing problem with the run.
Nothing blocking the pipe anywhere removes deposit and obstruction from the explanation entirely.
A drain disconnected and reconnected during the work is the only thing that actually changed.
A section left with too little fall holds water in place instead of carrying it away.

Why it happens

A condensate drain works on a small continuous fall, and it has no margin at all to give away. Reconnecting a pipe a few millimetres higher than it was flattens the first section of the run, and water then sits there rather than moving along it. The pipe is undamaged, the line is clear, and everything about the connection looks entirely correct. Only the height it sits at has changed.

What resolution involves

The connection is remade at the height that restores fall along the whole run, and the line is proven with water before anything closes over it. Any drain that gets disconnected should be re-proven rather than assumed. The fall it had before the work does not carry over to afterwards.

How to tell it worked

Water sent through the reconnected run and watched leaving at the far end before any cover goes back on. A marginal gradient cannot be seen, so nothing except water passing the whole way actually settles it.

Before you approve a quote

A reconnected drain has a new fall to prove

Fall is set by where the pipe sits. Reconnecting a few millimetres higher can lose it entirely.
A line that drained for years and stopped after a service has had its position changed, not its contents.
Prove any reconnected drain with water before it is covered. The old fall does not carry over.

Questions this case answers

Can a drain pipe leak at a trunking joint without being cracked?

Because fall is set by exactly where the pipe sits, and reconnecting it a few millimetres higher flattens the first section. A drain has very little margin, so a change nobody would notice is enough to lose it.

How does the timing of a leak point at what caused it?

Send water down the reconnected run and watch it leave at the far end. A marginal gradient is not visible and not reliably measurable by eye, so water passing the whole way is the only thing that settles it.

What happens if a pipe is reconnected without restoring its fall?

Before anything closes over it. Once trunking or a ceiling goes back, correcting it means taking those finishes apart again, and nobody looks at a covered drain until water turns up somewhere it should not.

Can this be fixed without opening the ceiling?

Nothing at all in parts. The pipe is undamaged and the line runs freely, so what is needed is remaking the connection at the right height. The cost is the time taken to prove the run afterwards.

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