Sunken bathroom leakage

A practical decision sequence

Diagnose the cause, then verify the repair.

Use the site evidence to agree a project-specific method with the responsible engineer, concrete producer, manufacturer or specialist applicator.

01 / Symptom

What is happening?

Water appears below a toilet, bath or service shaft.

02 / Inspect and test

Evidence to collect

Separate supply and waste pipe testing from containment testing; inspect floor-wall and pipe details.

03 / Likely mechanism

Why it can fail

Failed pipe joints, incomplete waterproofing or an unsealed threshold may each produce similar stains.

04 / Technical response

Choose the system

Repair the source, waterproof the full box with compatible corner and penetration detailing, and reinstate drainage.

05 / Site execution

Control the application

Inspect substrate, corners, upstands and sleeves before filling the sunken area.

06 / Acceptance

Verify the result

Perform a controlled test before screed and tiling; record water level and duration per specification.

Avoid this shortcut

Do not fill and tile a sunken area before testing the concealed system.

These guides are editorial starting points, not a project specification. Confirm the design, product data, substrate conditions and inspection plan for the actual site.

Technical references

References inform the topic; they do not endorse a specific product for this project.