Prefabricated House Plumbing and Electrical Pre-embedding

The pre-embedding of plumbing and electrical systems in prefabricated houses requires adherence to standardized procedures and attention to key details, as outlined below:

I. Construction Sequence

The pre-embedding of plumbing and electrical systems should be carried out after the installation of the floor slab formwork and the completion of steel bar binding. Laying pre-embedded pipes at this stage can prevent damage to pre-embedded components or flattening of conduits during the handling of steel bars, ensuring smooth conduits in the later stages. If pre-embedding is done before steel bar binding, subsequent adjustments to the steel bars may cause displacement of the pre-embedded components. If pre-embedding is not carried out promptly after steel bar binding, it may become impossible to construct due to the covering of the floor slab with concrete.

II. Pre-embedding Contents

1. Electrical Pre-embedding: This includes the pre-embedding of bottom boxes for lighting circuits (such as installation points for ceiling lights) and the pre-embedding of conduits for the installation positions of electrical boxes. The positions of the bottom boxes should be determined based on the type of lighting fixtures. For example, ceiling lights in bedrooms are typically located at the center of the room, while those in kitchens should avoid the area above hanging cabinets.
2. Plumbing Pre-embedding: This covers the pre-embedding of sewage pipes in bathrooms, water supply pipes, and drainage pipes on balconies. Sewage pipes in bathrooms should have a reserved slope (usually not less than 1%) to ensure smooth drainage. Drainage pipes on balconies should be connected to rainwater pipes or sewage pipes to prevent odors.

III. Precautions

1. Accurate Positioning:
   • It is necessary to accurately mark the positions of plumbing and electrical points on the formwork of the ceiling or walls, including the positions of lights, sockets, and drainage pipes. For example, to confirm the position of a bedroom light, a cross can be drawn from the center of the ceiling. The position of wall sockets should be measured from the edge of the formwork (e.g., 300mm from the floor). The position of sewage pipes in bathrooms should be measured from the edge of the formwork (e.g., 300-400mm from the wall for toilet sewage pipes).
   • After marking, use paint to draw the outlines of the points on the formwork. After formwork removal, the positions can be quickly located through the traces, avoiding structural damage caused by later slotting. When installing wire boxes, they should be fixed to the formwork or steel bars to prevent displacement during concrete pouring.
2. Secure Pre-embedding Installation:
   • Electrical conduits should be fixed to the steel bars with iron wires or nails at intervals not exceeding 1m to prevent displacement or cracking of the conduits due to concrete vibration. If the intersections of conduits are not fixed, it may result in exposed conduits or inability to thread wires after concrete pouring.
   • Pre-embedded plumbing components (such as sewage pipes in bathrooms) should be filled with sand to prevent cement mortar from penetrating and causing a reduction in pipe diameter or blockage. After filling with sand, the ends should be sealed with tape to prevent sand from scattering.
3. Qualified Joint Treatment:
   • The joints of conduits should be fixed with special glue or lock nuts to ensure tight joints and prevent concrete from penetrating. Loose joints may cause difficulties in threading wires later or damage to the insulation layer of the wires.
   • Water pipe joints should be connected by hot melting or sealed with rubber rings to ensure no leakage. For example, when hot melting PPR water pipes, the temperature (260±10℃) and time (5-10 seconds) should be controlled to avoid false welding or over-melting.