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Older Block Leaked After Wash: Pump Discharge Tube Crimped

An older block unit leaks after a wash. Some damage happens during reassembly, once nobody is watching any more.

By Team Snowflake | Updated 24 Aug 2026

How this presents

Overflowing at a unit after a wash, while the pump runs and the drain line stays clear. Very little water actually moves despite the pump running strongly. Everything worked when the cover went back on.

Setup
Sharp Wall-mounted4-6 yearsHDBBukit Merah
Misread as
A pump no longer keeping up with what it has to move, on equipment in an older block.
Check first
The route of the flexible tubing checked after the cover has gone back on

What else produces this

A pump running strongly while moving almost nothing means what it is pushing into is restricted, and the restriction is close by. Flexible tubing leaving a pump chamber has to follow a specific route to clear the cover. Anything sitting out of that route is pinched when the cover closes, which is why everything worked right up until the last step of the job. Taking the cover off and looking at the tube's path shows it immediately.

  1. A pump running strongly while moving little water points at a restriction on its outlet side.

  2. A clear drain line beyond the pump removes any obstruction further along the run.

  3. Tubing crimped where it leaves the chamber restricts flow at the closest possible point.

  4. Correct operation until the cover went back places the damage at that final step.

Why it happens

A cover has to close onto a chamber with tubing passing out of it, and there is one route that leaves the tube clear. Positioned slightly outside it, the tube is trapped as the cover is fitted and crimped flat. The pump then pushes against a restriction it cannot overcome, running hard and moving very little. Nothing about the closed cover shows what is happening underneath it.

What resolution involves

The cover comes off, the tube is routed correctly, and the cover goes back with the route checked afterwards rather than before. That order is the whole point: everything looks right while the cover is off, and the damage is done by closing it. A function test after the cover is on catches what a look before it never will.

How to tell it worked

The pump run with the cover fitted and the water actually watched arriving at the far end. A pump pushing into a crimped tube still runs and still sounds correct, so listening to it proves nothing at all.

Before you approve a quote

The cover can crimp what it closes over

  • Flexible parts are positioned with everything open. The cover is the last thing to move against them.
  • Everything working before the cover goes on is not evidence. That is when the damage is done.
  • Test after the cover is fitted, not before. A crimped tube leaves a pump sounding perfectly normal.

Questions this case answers

Can a drain pump still be working even though my flat is leaking?
Because the cover is the last thing to go on and it moves against whatever is inside. A tube sitting slightly outside its intended route gets trapped and flattened as the cover closes over it.
How does a crimped drain tube cause a leak days later rather than straight away?
It runs hard and moves very little. Pushing into a restriction it cannot overcome, the motor sounds entirely normal and sometimes louder than usual, so listening to it gives no indication of the problem.
What happens if the pump gets replaced but the tube stays crimped?
Take the cover off, route the tube correctly, and refit the cover. Nothing needs replacing unless the tubing has been creased badly enough to stay flattened once the pressure comes off it.

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