40mm pvc pipe fittings basics
Material properties and manufacturing process
40mm pvc pipe fittings use unplasticized polyvinyl chloride (PVC-U) as the main raw material and are processed by precision injection molding. This material has the following significant characteristics:
Chemical stability: excellent acid and alkali corrosion resistance, pH value applicable range can reach 2-12
Physical properties: density 1.35-1.46g/cm³, tensile strength ≥40MPa
Thermal properties: Vicat softening temperature ≥79℃, operating temperature range 0-45℃
Fluid properties: smooth inner wall, friction coefficient of only 0.009, excellent hydraulic properties
The manufacturing process requires multiple processes such as raw material ratio, high temperature plasticization, mold injection, cooling and shaping. High-quality products should be produced with new materials and avoid the use of recycled materials to ensure the mechanical strength and long-term durability of the products.
Standards and quality requirements
40mm pvc pipe fittings must comply with relevant national standards:
GB/T 5836.1-2018 “Rigid polyvinyl chloride (PVC-U) pipes for building drainage”
GB/T 5836.2-2018 “Rigid polyvinyl chloride (PVC-U) pipe fittings for building drainage”
CJ/T 250-2018 “Technical regulations for plastic pipe engineering for building drainage”
Key quality indicators include:
Dimensional accuracy: outer diameter tolerance ±0.2mm, wall thickness deviation ≤12%
Mechanical properties: no cracks in the drop hammer impact test, hydraulic test withstands 0.6MPa pressure
Appearance quality: smooth inner and outer walls, no bubbles, cracks and other defects
Product classification and structural features
Classification by function
Steering connection type:
90° elbow: divided into long diameter type (R=2.5D) and short diameter type (R=1.5D)
45° elbow: used in situations where smooth steering is required
Double elbow joint: combine different angles to achieve complex steering
Branch connection type:
Equal diameter tee: all three interfaces are 40mm
Reducing tee: main pipe 40mm, branch pipe can be equipped with small specifications such as 32mm
Oblique tee: 45° branch, reduce fluid resistance
Four-way fittings: used for cross-pipe connection
Reducing connection type:
Concentric reducer: reducer connection with consistent center line
Eccentric reducer: used in situations where the bottom or top of the pipe needs to be kept flush
Special function type:
Water trap: P-type, S-type, bottle-type and other odor-proof designs
Inspection port: with removable cover for easy pipeline dredging
Expansion joint: compensate for thermal expansion and contraction of pipeline, expansion amount ≥10mm
Classification by connection method
Socket bonding:
Most common connection method
Socket depth ≥25mm
Need to be used with special PVC glue
Threaded connection:
Mainly used for connection with metal pipe fittings
Divided into internal thread and external thread
Need to be used with sealing tape
Flange connection:
Used in areas that require frequent disassembly
Flange thickness ≥10mm
Need to be matched with rubber gasket
Key points of engineering design
Hydraulic calculation principles
Flow calculation:
Drainage capacity at full flow Q=8.5L/s (slope 1%)
Actual design should be calculated based on 50-75% full flow
Slope requirements:
Minimum slope of indoor drainage pipe:
DN40 horizontal pipe: 2.6% (1:40)
Branch pipe: 4.2% (1:25)
Minimum slope of outdoor drainage pipe 1.5%
Flow rate control:
Self-cleaning flow rate ≥0.6m/s
Maximum flow rate ≤2.5m/s
Pipeline layout specifications
Space requirements:
Distance from the wall ≥ 20mm
Clear distance when crossing ≥ 50mm
Center distance when parallel ≥ 80mm
Support spacing:
Horizontal pipe:
40mm pipe: bracket spacing ≤ 800mm
Brackets should be installed within 300mm at the corner
Vertical pipe:
At least one fixed bracket per floor
No need to install when the floor height is ≤ 4m
Expansion compensation:
Straight pipe sections exceeding 4m should be equipped with expansion joints
Expansion amount is calculated according to ΔL=0.07×L×Δt
Distance between fixed brackets ≤ 10m
Installation and construction technology
Pre-construction preparation
Material acceptance:
Check product certificates and test reports
Measure whether the pipe dimensions meet the requirements
Perform appearance quality inspection
Tool preparation:
Special PVC pipe scissors or cutting machine
Chamfering machine
Sandpaper (80-120 mesh)
Special PVC glue and brush
On-site measurement:
Use the “actual measurement” method
Draw a detailed diagram of the pipeline direction
Calculate the length of each section
Standard installation process
Pipe cutting:
Use special cutting tools
Ensure that the cut is straight and burr-free
The vertical deviation of the cut is ≤1°
Interface processing:
Grind the socket and the plug with sandpaper
Grinding length ≥ socket depth
Remove the surface oxide layer
Gluing process:
Try assembly first and mark the insertion depth
Apply glue evenly (first socket and then plug)
Quickly insert and rotate 90°
Maintain pressure for 10-15 seconds
Wipe off excess glue
Curing time:
Summer: 30 minutes to move
Winter: 60 minutes to move
Full curing requires 24 hours
Special parts treatment
Wall penetration treatment:
Buried steel casing
Casing diameter is two sizes larger
Fill the gap with flexible material
Expansion joint installation:
Install between fixed brackets
Set position ≤500mm from tee
Reserve expansion gap
Water trap installation:
Water seal depth ≥50mm
Cleaning port at the bottom
Avoid multiple water traps in series
Common problem analysis and treatment
Installation quality problem
Leakage problem:
Cause analysis:
Uneven glue application
Insufficient insertion depth
Insufficient curing time
Solution:
Minor leakage can be repaired with glue
Serious leakage requires replacement
Poor drainage:
Cause analysis:
Insufficient slope
Too many turns
Improper pipe diameter selection
Solution:
Check whether the slope meets the requirements
Optimize the direction of the pipeline
Problems during use
Pipe blockage:
Preventive measures:
Flush regularly
Install cleaning ports
Avoid discharge of debris
Treatment methods:
Mechanical dredging
High-pressure water flushing
Frost cracking in winter:
Protective measures:
Strengthen insulation
Maintain drainage
Add antifreeze
Maintenance methods:
Replace cracked pipe sections
Improve insulation measures
Aging problem
Ultraviolet aging:
Performance: Surface powdering and brittleness
Protection: Avoid direct sunlight
Treatment: Apply protective coating
Chemical corrosion:
Performance: Surface swelling and discoloration
Protection: Avoid contact with organic solvents
Treatment: Replace affected pipe sections
This technical guide comprehensively covers all aspects of 40mm pvc pipe fittings, from basic theory to practical application, from conventional installation to use, providing a systematic reference for engineering and technical personnel. In actual application, appropriate adjustments should be made according to specific engineering conditions and the latest technical standards to ensure the safety, reliability and long-term stable operation of the pipeline system.
