Selecting between pipe sleeves and pre-embedded proprietary water-stop joints where building water supply and drainage pipes pass through floor slabs (and walls): mandatory sleeve requirements, scenario-based selection, and the conditions on which a UPVC plastic drainage pipe may substitute a water-stop joint for a sleeve

Topic Positioning

How to choose between sleeves and pre-embedded proprietary water-stop joints where building water supply and drainage pipes pass through floor slabs (and walls and basement exterior walls); whether substituting a pre-embedded water-stop joint for a sleeve is valid for UPVC (plastic) drainage pipes, and what conditions must be met. Intended for detailed design and construction-method determinations on water supply and drainage pipework in residential and public buildings.

Core Conclusions

1. Code basis

1. GB 55020-2021 "General Code for Water Supply and Drainage and Water Conservation of Buildings", clause 8.2.3 (full-text mandatory): "Where pipes pass through walls and floor slabs, metal or plastic sleeves shall be provided. The top of a sleeve installed within a floor slab shall be 20mm above the finished floor; the top of a sleeve installed within a bathroom or kitchen shall be 50mm above the finished floor, and its bottom shall be flush with the soffit of the slab; a sleeve installed within a wall shall have both ends flush with the finished faces. The gap between a slab-penetration sleeve and the pipe shall be packed tight with flame-retardant dense materials and waterproofing mastic, with smooth end faces. The gap between a wall-penetration sleeve and the pipe should be packed tight with flame-retardant dense materials, and the end faces shall be smooth. Pipe joints shall not be located inside sleeves." The same clause also requires that pipes and joints be kept clean during installation, that construction debris be strictly prevented from falling into pipes, that pipe joints not be located inside sleeves, and that open pipe ends be temporarily sealed when work is interrupted or completed. The reason joints are barred from sleeves: a leaking joint inside a sleeve is hard to detect and hard to repair or replace.
2. GB 50015-2019 "Standard for Design of Building Water Supply and Drainage", clause 3.6.18 (water supply): "Where exposed water supply risers pass through floor slabs, waterproofing measures shall be taken. Where pipes pass through walls and floor slabs, metal or plastic sleeves shall be provided... pipe joints shall not be located inside sleeves."
3. Drainage riser basis: GB/T 51188-2016 clause 10.5.11 - "Reliable waterproofing measures shall be taken where drainage risers pass through floor slabs; where plastic drainage risers pass through floor slabs or fire walls, fire-protection sleeves and fire collars shall be provided. Where drainage pipes pass through basement exterior walls and roof slabs, waterproofing sleeves or other effective waterproofing measures shall be adopted"; CJJ 232-2016 clause 3.4.4 - "Waterproofing measures shall be taken where drainage risers pass through floor slabs. Sleeves shall be provided where horizontal drainage pipes pass through indoor load-bearing concrete or masonry walls or exterior walls. Waterproofing sleeves shall be provided where horizontal drainage pipes pass through basement exterior walls."

2. Scenario-based selection

• Plastic (UPVC) drainage pipes through floor slabs: pre-embedded water-stop joints are preferred. DB1331/T 050-2023 clause 8.3.6: "Where pipes are laid through floor slabs, the penetration shall not leak... plastic drainage pipes should use pre-embedded water-stop joints, with the deviation of pre-embedded joints between adjoining floors not exceeding 20mm; metal drainage pipes shall have pre-embedded steel sleeves one to two sizes larger than the pipe, with the deviation of pre-embedded steel sleeves between adjoining floors not exceeding 20mm."
• Metal drainage pipes (cast iron etc.): pre-embedded steel sleeves; DB11/T 364-2023 clause 4.1.5 - slab-penetration sleeves in kitchens, bathrooms and plant rooms shall stand 50mm above the room floor and 20mm above elsewhere; the sleeve bottom shall be flush with the slab soffit; the gap between sleeve and cast-iron pipe shall be packed with flexible sealing material before sealing; waterproofing sleeves shall be provided where pipes pass through basement exterior walls and pool walls.
• Kitchens and sanitary rooms, floor penetrations (DB11/T 1811-2020 clause 5.3.6): "The sleeve method or the thrust-through method is preferred; the sleeve top shall be 20mm above the finished floor and its bottom flush with the slab soffit; the sleeve inner diameter shall be 2mm to 5mm larger than the riser outer diameter. Sleeves with water-stop rings should be used, with a 20mm x 15mm groove reserved around the sleeve and filled tight with sealant."
• Penetrating structural waterproofing layers (DB11/T 1811-2020 clause 5.7.4): where structural movement or pipe expansion is small, direct embedding may be used; where it is larger, or replacement is required, the sleeve type shall be used; pipes and sleeves embedded in structural concrete shall have water-stop rings welded on and hydrophilic water-stop strips bonded; waterproofing sleeves shall stand at least 20mm above the finished decorative level, the sleeve-pipe gap shall be caulked and compacted with waterproof sealing material, and the sleeve shall be embedded before concreting; a 10mm wide x 15mm deep groove shall be left in the concrete surface around the pipe and sleeve and filled with sealant.
• Different-floor drainage through slabs (DB11/T 1811-2020 clause 5.5.10): seepage-prevention measures such as water-stop rings and rubber sealing rings shall be taken.
• Industrialised buildings (T/CCES 28-2021 clause 4.3.9): "Where drainage pipes pass vertically through structural floor slabs, pre-embedding is preferred, and connection joints shall not be buried in the structural slab"; integral (extended) combined fittings should be used so that no joint lies at the penetration, and pre-embedded sleeves or fittings with adjustable centres and water-stop functions should be used.

3. Determining whether a UPVC water-stop joint may replace a sleeve (all conditions must be met)

1. Material match: applies to plastic (UPVC) gravity-flow drainage pipes only; not to water supply pipes or metal drainage pipes - supply pipes through slabs take metal or plastic sleeves, and metal drainage pipes take pre-embedded steel sleeves.
2. Permissible location: ordinary floor slabs and wet rooms such as bathrooms and kitchens are acceptable; locations with waterproofing requirements - basement exterior walls, pool walls and the like - require waterproofing sleeves, and fire-separation penetrations are treated as fire stopping; in none of these may a water-stop joint substitute.
3. Design approval (prerequisite): GB 55020-2021 is a full-text mandatory code whose wording is "metal or plastic sleeves shall be provided"; unilateral substitution by the contractor is non-compliant - the design drawings must expressly state "pre-embedded water-stop joints", or a design technical verification / variation must be processed before implementation.
4. Pre-embedding workmanship: the level deviation of pre-embedded water-stop joints between adjoining floors shall not exceed 20mm; connection joints shall not be buried within the structural floor slab.
5. Fire requirements are not waived: the annular gaps of slab and fire-wall penetrations of metal drainage pipes and their sleeve gaps shall be sealed with fire-resistant materials; fire-stop devices for plastic drainage pipes (GB 50015-2019 clause 4.4.10) - where pipes cross fire walls, devices shall be fitted on the pipe on both sides of the wall; in high-rise buildings, exposed drainage risers of dn110 and above crossing floor slabs shall have a device on the pipe below the slab; where pipes pass through shaft walls, the device shall be on the pipe outside the wall; fire collars shall comply with GA 304.

Applicability Boundaries

• The conclusion on substituting a water-stop joint for a sleeve holds only for plastic gravity-flow drainage pipes; pressure supply pipes, metal drainage pipes and locations requiring replacement access are excluded.
• GB 55020-2021 clause 8.2.3 is a full-text mandatory provision; any material-substitution practice requires design approval and must not be changed unilaterally by the contractor.
• Local standards (DB11/T 1811-2020, DB11/T 364-2023, DB1331/T 050-2023) apply within their respective administrative regions; elsewhere the currently effective local standards govern.
• Sleeves and sealing details at special locations such as civil-defence works and fire compartments follow the dedicated codes and are not covered by this card.

Further Reading

• GB 55020-2021 clause 8.2.3 (construction and acceptance; pipes through walls and slabs)
• GB 50015-2019 clauses 3.6.18 (water supply) and 4.4.10 (soil and waste drainage)
• GB/T 51188-2016 clause 10.5.11; CJJ 232-2016 clause 3.4.4
• DB1331/T 050-2023 clause 8.3.6; DB11/T 1811-2020 clauses 5.3.6, 5.5.10, 5.7.4; DB11/T 364-2023 clause 4.1.5; T/CCES 28-2021 clause 4.3.9; GA 304 "Fire collars for plastic pipes"