The design of a composite board bathtub's bottom drainage structure must strike a balance between drainage efficiency and structural strength. The key approach is to optimize the drainage path and reduce resistance, while also enhancing compressive strength through material selection and structural reinforcement. Improving drainage efficiency requires coordinated optimization of three aspects: drain outlet layout, pipe slope, and anti-clogging design. The drain outlet is typically located at the lowest point of the bathtub's base. Its placement should be considered in conjunction with fluid dynamics simulations of the bathtub's overall shape to ensure natural water flow and avoid localized water accumulation. For example, the drain outlet of an oval bathtub is often located near the midpoint of the long axis, while the drain outlet of a rectangular bathtub is offset to one of the short sides to shorten the water flow path. The pipe slope is a key factor influencing drainage efficiency. A 2%-3% inclination angle with the horizontal is generally recommended to accelerate water flow by gravity while avoiding stress concentration at the pipe-bathtub connection caused by excessive slope. Anti-clogging design requires the addition of a filter at the drain outlet, such as a removable metal screen or plastic grate, to trap debris such as hair and soap residue before they enter the pipe and cause blockage.
Ensuring structural strength requires careful consideration of material selection, thickness control, and support structures. Composite board bathtubs are often made of glass fiber reinforced plastic (GFRP) or acrylic and resin composites. These materials are lightweight and high-strength, but impact resistance requires a well-thought-out lamination process. For example, the base of a GFRP bathtub typically features multiple layers of alternating glass fiber, with a locally thickened layer around the drain to dissipate the impact of water flow. Regarding thickness control, the central area of the bathtub base should be appropriately thickened to withstand the hydrostatic pressure of a full bathtub, while the edges can be gradually tapered to reduce weight. The support structure design should be tailored to the bathtub's installation method. For floor-standing installations, reinforcing ribs or a honeycomb support structure should be incorporated into the base to enhance overall rigidity. For built-in installations, a fixed connection to the wall or base should be used to distribute the load and prevent localized deformation.
The connection process between the drain and the bathtub body directly impacts sealing and durability. Traditional connection methods often rely on gluing or hot-melt welding, but these are prone to cracking after long-term use due to material aging and temperature fluctuations. Modern composite-board bathtubs often utilize an integrated molding process, with the drain opening and tub bottom molded simultaneously, eliminating seams and preventing leaks at the source. For bathtubs requiring later installation of drainage components, a double-layer sealing design is required at the joints: an inner silicone sealant and an outer layer coated with waterproof silicone sealant. Clamps or bolts are used to secure the seal, ensuring a seal that maintains performance despite long-term vibration and temperature fluctuations.
The material selection for the drainage pipe should balance corrosion resistance and internal smoothness. PVC pipes are the mainstream choice for bathtub drainage systems due to their low cost and strong resistance to acid and alkali corrosion. However, their rough interior surface makes them susceptible to dirt accumulation. Stainless steel pipes, while smooth and offering low drainage resistance, are more expensive and require electrochemical polishing for improved corrosion resistance. Some high-end bathtubs utilize a co-extrusion process, applying a nano-level antimicrobial coating to the inner surface of the PVC pipes. This reduces roughness, inhibits bacterial growth, and extends the pipe's lifespan.
An odor-resistant design for the drainage system should be implemented through a trap or water seal. The water stored in the trap forms a liquid seal, preventing odor from seeping back into the drainpipe. The structure must ensure a water seal height of at least 50mm to prevent negative pressure from disrupting the seal. For drainage systems without a trap, a magnetic anti-odor valve can be installed below the drain outlet. This valve uses magnetic force to control the opening and closing of the valve disc, automatically opening during drainage and closing when drainage stops, blocking the passage of odor.
Drainage structures should be made more maintainable through modular design. Connections to the drain outlet, filter, and drain pipe should utilize quick-release features, such as snap-on or threaded connections, to facilitate regular cleaning of debris and replacement of aging components. Some bathtubs feature an inspection hatch below the drain outlet that can be opened by rotating a cover, eliminating the need to disassemble the entire bathtub and significantly simplifying maintenance.
The design of composite board bathtub bottom drainage structures requires simulation analysis to optimize performance. Finite element analysis (FEA) can be used to simulate the stress distribution of the bathtub bottom when full of water, accurately locating high-stress areas and mitigating risks by adjusting material thickness or support structures. Computational fluid dynamics (CFD) simulation can analyze the vortex of water near the drain outlet, optimize the shape of the drain outlet, reduce water flow resistance, and improve drainage efficiency.
