P-Trap Back-to-Wall Smart bidet Toilet: Installation Guide & Requirements

In Hong Kong, the P-Trap (wall-drain) configuration is the gold standard for residential plumbing. If you are planning to upgrade your bathroom with a Back-to-Wall (BTW) Smart Toilet, technical precision is the key to success. Unlike traditional toilets, smart models require integrated plumbing and electrical planning.

This guide outlines the four essential requirements to ensure a seamless and professional installation.

1. The "180mm" Rule: Waste Outlet Height

The most critical measurement for any P-Trap installation in Hong Kong is the waste outlet height. Most modern private estates and residential buildings follow the 180mm standard (measured from the finished floor to the center of the waste pipe in the wall).

• The Risk: If your wall outlet is significantly higher or lower than the toilet’s discharge point, a floor-standing model will either hover off the ground or require unsightly offset connectors that prevent the toilet from sitting flush against the wall.

• Pro Tip: Always verify your site’s specific "P-height" before purchasing to ensure a perfect horizontal alignment.

2. Dual-Inlet System: Salt and Fresh Water Split

Hong Kong has a unique plumbing regulation that every smart toilet owner must address: the separation of water sources.

• Salt Water for Flushing: Standard building supply used to clear the bowl.

• Fresh Water for Cleansing: Filtered water used for the bidet spray nozzles.

• Requirement: Ensure your chosen smart toilet supports a Dual-Inlet System. You must have two separate shut-off valves behind the toilet to comply with Water Supplies Department (WSD) hygiene standards and protect your health.

3. Electrical Preparation: The 13A Waterproof Socket

A smart toilet is an electronic appliance. It requires a stable power source for the heated seat, warm air dryer, and auto-flush sensors.

• Specifications: You must install a 13A waterproof (IP-rated) socket with a protective cover.

• Positioning: The socket should ideally be placed 15cm to 30cm away from the side of the toilet and at a height that avoids water splashes. Ensure the circuit is properly earthed (grounded) to prevent electrical hazards in the humid bathroom environment.

Conclusion: Plan Early for a Five-Star Result

A P-Trap Back-to-Wall Smart cidet Toilet is the ultimate upgrade for hygiene and aesthetics. By coordinating your outlet height(180mm), dual-inlet valves, and 13A power supply during the early stages of your renovation, you can avoid costly modifications and enjoy a sleek, high-tech bathroom that functions as beautifully as it looks.