Precautions for Indoor Water Supply and Drainage Pipe Installation

Layout of Water Supply Pipes

1. Inlet Pipes

   To ensure water supply balance and reliability, inlet pipes should be installed from the area with the highest water demand or where uninterrupted supply is required.

   If water usage points are evenly distributed, the inlet should be located in the middle of the building to reduce pipeline length and minimize head loss.

   Number of inlets: Normally one; when uninterrupted supply is required or if more than 10 fire hydrants are installed, two inlets should be used, preferably from different sides of the building. If installed on the same side, the spacing should be more than 10 m.

   Outdoor pipes should be buried below the frost line (at least 0.2 m lower) and covered with 0.7–1.0 m of soil. Indoors, pipes should pass through or under the foundation.

2. Water Meter Location

   In northern regions: inside a load-bearing wall.

   In southern regions: inside a water meter pit.

3. Indoor Water Supply Network

   Pipes should be as short as possible, run in straight lines, and be parallel to walls, beams, and columns for better aesthetics and easier maintenance.

   Main pipes should be close to major users or critical points to ensure reliable supply and reduce the length of large-diameter pipes.

   Pipes must not be installed inside drainage rooms, flues, or ventilation ducts, nor pass through toilets, display cabinets, wardrobes, or wooden structures.

   Settlement joints should be avoided. If crossing is necessary, proper technical measures must be taken.

   In workshops, pipes may be overhead or underground. Overhead pipes should not interfere with production or traffic, nor pass above flammable or explosive materials. Underground pipes should avoid equipment foundations to prevent crushing or vibration damage.

Pipe Installation Methods

Depending on the building’s hygiene and aesthetic requirements, pipes may be installed in two ways:

1. Exposed Installation

   Pipes are mounted along walls, beams, columns, ceilings, or floors.

   Advantages: low cost, easy installation and maintenance.

   Disadvantages: poor aesthetics, prone to condensation, dust accumulation, and hygiene issues.

2. Concealed Installation

   Pipes are hidden in basements, ceilings, pipe shafts, pipe trenches, or ducts.

   Features: better sanitation and appearance, but higher cost and more difficult maintenance.

   Applications: high-standard buildings (e.g., high-rises, hotels), and clean workshops (e.g., precision instruments, electronics).

When installed in parallel or crossing with other pipelines, relative position, spacing, and supports must be arranged according to integrated pipeline design requirements.

3. Inlet Pipe Requirements

   Outdoor pipe tops must be 20 cm below the frost line with 0.7–1.0 m soil cover.

   Where pipes pass through walls or foundations, reserved holes should be made with a diameter of pipe size + 200 mm.

4. Water Meter Nodes

   Northern regions: first load-bearing wall.

   Southern regions: water meter pit.

   Requirements: ambient temperature above 2℃, easy maintenance, safe from contamination or damage.

Technical Measures: Anti-Corrosion, Anti-Freezing, Anti-Condensation, and Anti-Leakage

To ensure long-term operation of indoor water supply systems, both regular maintenance and construction measures must be applied:

1. Anti-Corrosion

   Except for galvanized steel pipes, all exposed and concealed pipes require anti-corrosion treatment.

   Steel pipes: use methods such as rust removal, anti-rust paint, primer, and asphalt coatings. Multi-layer protection may include primer, asphalt mastic, waterproof sheets, or paper wrapping.

   Cast iron pipes: underground pipes must be coated with asphalt.

   Exposed pipes: painted with red lead primer and silver paint.

   Internal protection: for corrosive liquids, use corrosion-resistant materials or apply internal linings such as rubber or fiberglass-reinforced coatings.

2. Anti-Freezing

   Avoid installing pipes in areas prone to freezing.

   For cold regions: insulate roof water tanks, unheated indoor pipes, or pipes in halls and corridors with materials such as mineral wool or glass wool.

3. Anti-Condensation

   In hot and humid rooms (e.g., bathrooms, laundries), condensation can form on cold water pipes, causing wall damage and pipe corrosion.

   Solution: add moisture-proof insulation layers around pipes, typically combined with thermal insulation.

Water Quality Protection

1. Each water supply system (domestic water, drinking water, and miscellaneous water) must be independent and not interconnected.

2. Domestic water systems must prevent backflow contamination.

3. Secondary water supply tanks must be independent, with storage capacity not exceeding 48 hours of water consumption. Overflow from other systems is prohibited.

4. Underground domestic water tanks must be at least 10 m away from septic tanks or sewage treatment structures.

5. Indoor domestic water tanks must be independently constructed, not using building structures as tank walls, bases, or covers.

6. If domestic water tanks are installed alongside other water tanks, independent walls must be used, and leakage between walls must be drained naturally.

7. Domestic water tanks must be installed in dedicated rooms, with no toilets, kitchens, or sewage facilities located above them.

8. Tank and pipeline requirements:

   Materials must be non-toxic and non-polluting.

   Tanks must have sealed covers and lockable manholes; vent pipes must not connect with other rooms.

   Inlet and outlet pipes should be on opposite sides to avoid short-circuiting, with flow guide devices if necessary.

   Vent and overflow pipes must have insect-proof mesh and must not connect with drainage vents or ducts.

   Overflow and drain pipes must not directly connect with drainage systems and should have an air gap of at least 0.2 m.

Indoor water supply and drainage pipe installation not only affects the building’s function but also directly impacts residents’ quality of life and water safety. Proper planning of pipeline layout, installation methods, technical measures, and water quality protection is essential to ensure safe, efficient, and long-lasting operation of the system.