Sanitary & Drainage Systems

Sanitary and drainage systems carry waste water from fixtures to the public sewer: sanitary fixtures (toilets, basins, sinks, showers, urinals), traps, above-ground pipework and stacks, vents that protect trap seals, in-ground drainage, inspection openings and access chambers, and the connection to the sewer. Wet area waterproofing in bathrooms and showers is included because its failure presents as a drainage problem. Stormwater drainage, trade waste and pumped systems have their own pages.

What shortens life:

• Tree roots seeking water through joints in clay and older pipes.
• Ground movement from reactive clays, settlement and nearby excavation.
• Fats, oils, wipes and debris flushed into the system.
• Hydrogen sulphide corroding cast iron and concrete from inside.
• Poor wet area waterproofing installed with the building.

Root intrusion and joint failure

Roots enter through joints in clay and older pipes, grow into mats that catch debris, and crack and displace pipes as they thicken. Joints displaced by ground movement leak into the ground, undermining foundations and paving, and let roots in.

Cast iron corrosion

Cast iron corrodes from the inside, worst along the crown of horizontal pipes where hydrogen sulphide gas collects, and along the invert where water runs. Pipes crack lengthwise and leak in ceilings and walls; many mid-century apartment buildings are now replacing cast iron stacks.

Collapse and deformation

Pitch fibre pipes deform into ovals and collapse; asbestos cement and clay crack under load or ground movement. Collapsed drains cause blockages, leaks into the ground and subsidence.

Blockages

Fats, wipes, sanitary products and debris block drains, especially at bellies (sags) where water and solids sit. Repeated blockages at the same place usually point to a defect in the pipe.

Venting failures

Vents protect trap seals from being siphoned. Blocked, removed or undersized vents let traps empty, bringing sewer gas and odour into the building; air admittance valves fail closed or open.

Wet area leaks

Bathroom and shower waterproofing fails at floor wastes, wall-floor junctions and around penetrations; water soaks into floors and walls, rots timber, corrodes steel, and leaks into the floor below. In apartment buildings it is among the most common defects.

Sewer surcharge and backflow

When the public sewer surcharges in heavy rain, sewage can back up into the lowest fixtures. Overflow relief gullies and backflow valves protect against this; where they are missing or below floor levels set incorrectly, basements and ground floors flood with sewage.

On site

• Pipe materials in risers, ceilings and plant rooms; cracks and rust on cast iron.
• Odour of sewer gas in bathrooms and corridors.
• Slow drains and gurgling fixtures.
• Damp, stained or swollen skirtings and floors around showers and toilets.
• Cracked tiles and failed grout at shower floors.
• Wet patches, subsidence or lush growth over drain runs outside.
• Inspection openings and chambers: accessible, covers intact.

In the records

• CCTV drain surveys.
• Blockage and plumber call-out history by location.
• Defect claims for wet areas.
• Sewer authority correspondence.
• As-built drainage drawings.

• Repeated plumber visits to the same stack or drain run, recorded by unit or tenancy.

Findings are graded by what they demand: safety (can hurt someone now), failure (failed and damaging the building), condition (distress present and progressing), lifecycle (renewal due on age and exposure), deadline (a regulator or ordinance sets the date), check (investigate before sizing works) and nil (cosmetic or stable).

A licensed plumber or drainage contractor leads; a hydraulic engineer joins for larger buildings, stack replacement programmes and where drainage is implicated in subsidence.

• CCTV survey of in-ground drains and the main stacks, with each defect coded to the industry system (WSA 05 in Australia, the MSCC in Britain, NASSCO PACP in the United States), located by distance and depth, and recorded on a plan.
• Smoke testing of stacks and vents to locate leaks, dry traps and the source of sewer odours.
• Dye and flood testing of bathrooms and showers to separate membrane failure from pipe leaks.
• Cast iron sampling: remove a short section from representative stacks to measure remaining wall thickness, which sets the replacement horizon for the whole building.
• Backflow review: levels of overflow relief gullies and the lowest fixtures against the sewer, and the presence of backflow valves.
• Fixture survey for condition, water efficiency and accessibility.

The report should give the condition of each drain run and stack with defects located, the cause of recurring blockages, wet area findings, backflow risk, and options for relining, repair or replacement.

• Relining drains and stacks with cured-in-place liners, which avoids excavating under slabs and opening finishes in occupied apartments, provided the host pipe is still round and continuous.
• Patch repairs at isolated defects such as a single displaced joint or root entry point.
• Excavation and replacement where drains have collapsed, are badly displaced, or are pitch fibre.
• Root management: cutting and jetting as interim measures, followed by relining or replacement to stop recurrence.
• Stack replacement in apartment buildings, programmed riser by riser with temporary arrangements for residents.
• Wet area rectification: strip tiles and screed, re-waterproof with correct falls, upturns and waste flanges, and retile.
• Vent repairs, including replacement of failed air admittance valves.
• Backflow protection: overflow relief gullies at the right level and backflow valves on low fixtures.
• Fixture replacement with water-efficient fittings, reducing water use and sometimes drain loading.

CCTV surveys and smoke tests are lump sums per building or per run. Relining is priced by length and diameter; excavation and replacement by length and depth, with surface reinstatement (paving, landscaping, slabs) often the largest part. Stack replacement is priced per stack or per floor, with access through apartments and making good of finishes. Wet area rectification is priced per bathroom. Blockage clearing is reactive maintenance whose frequency tells you where capital is needed.

Replacement and relining are lifecycle; patch repairs and clearing are repairs and maintenance; backflow protection and wet area rectification can be code compliance or defect items.

• Australia. AS/NZS 3500.2 governs sanitary plumbing and drainage, including overflow relief gullies; AS 3740 governs wet area waterproofing in houses and the National Construction Code in other buildings; plumbing is licensed and certified; wet areas are a leading strata defect.
• United Kingdom. Approved Document H governs drainage; BS EN 12056 covers gravity drainage inside buildings and BS EN 752 drains outside; private sewers transferred to water companies in 2011 changed responsibility for shared drains.
• United States. The International and Uniform Plumbing Codes govern drainage; some regions require sewer lateral inspection and repair on sale or renovation; NASSCO sets pipeline condition coding.

• Ownership. In all three jurisdictions the boundary between owner and utility responsibility matters: in Australia the sewer connection point and boundary trap; in Britain, the 2011 transfer of private sewers and lateral drains to water companies; in the United States, private laterals up to the main. Strata and condominium buildings treat stacks and shared drains as common property, while fixtures and wet areas within units are often the owner's.

• CCTV drain surveys with coded defect reports and plans.
• Blockage and plumber call-out history by location.
• Wet area defect claims, flood test results and rectification records.
• As-built drainage drawings and sewer connection details.
• Sewer authority or utility correspondence, including lateral inspection notices.
• Records of relining, stack replacement or excavation repairs.
• Cast iron wall thickness test results where stacks are cast iron.