1. The Mandatory Dual-Pipe Plumbing Mandate
To conserve potable water resources, all new building designs in Dholera SIR must feature two independent water distribution systems:
- Potable Water Line (Blue Pipe): Conveys treated municipal drinking water supplied by DICDL. This line is restricted to kitchens, washbasins, showers, and drinking water outlets.
- Recycled Greywater Line (Green Pipe): Conveys recycled water from the building’s STP or municipal recycled supply. This line is connected exclusively to toilet flushing cisterns, laundry washing machines, and outdoor landscape irrigation outlets.
- No Cross-Connection: There must be no physical connection, bypass valve, or interlocking between the potable and recycled water lines to prevent contamination of the drinking water supply.
2. Drain Pipe Sizing and Flow Standards
The GDCR specifies minimum internal diameters for plumbing pipes to prevent blockages and maintain hydraulic pressure:
- Soil Waste Pipes (Water Closets): All pipes carrying fecal waste must have a minimum internal diameter of 100mm (black/grey PVC or cast iron).
- Sullage Waste Pipes (Sinks, Showers): Pipes carrying washwater must measure at least 75mm in diameter.
- Ventilation Stacks: To equalize air pressure and vent sewer gases safely above the roofline, vertical vent stacks must have a minimum diameter of 50mm or match the diameter of the primary discharge stack.
- Minimum Pipe Slope: Horizontal branch drains must be laid with a minimum slope of 1 in 50 for 75mm pipes and 1 in 100 for 100mm pipes to ensure gravity-flow velocity.
The table below outlines DSIRDA plumbing and sewer line sizing guidelines:
| Plumbing Component | Minimum Pipe Diameter | Mandatory Material Specification | Allowed Water Type | Required Installation Code |
|---|---|---|---|---|
| **Potable Water Riser** | 25mm – 50mm | CPVC / Copper (PN16 rated) | Treated municipal water | Insulated shut-off valves |
| **Recycled Water Riser** | 25mm – 50mm | Green PP-R / CPVC | Recycled greywater | Clearly marked “Recycled” |
| **Soil Stack (W.C. Drain)** | 100mm (4 inches) | Heavy-duty PVC (Type B) / CI | Sewage / Blackwater | Clean-out plug at bend |
| **Sullage Stack (Sinks)** | 75mm (3 inches) | UPVC / Lead-free PVC | Greywater runoff | Multi-trap siphon seal |
| **Vent Stack (Roof Vent)** | 50mm (2 inches) | PVC (weatherproof UV stable) | Air / Sewer gases | Terminate 1.5m above roof |
3. Grease Traps and Backflow Prevention
- Grease Traps for Commercial Kitchens: Restaurants, hotels, and food courts must install a multi-chamber grease interceptor on their kitchen waste line before it joins the primary sewer. The trap must capture fats, oils, and grease (FOG) to prevent pipeline blockage.
- Municipal Backflow Preventer: Every property’s sewer connection to the DICDL municipal main must feature a non-return check valve (NRV). The NRV prevents municipal sewage from backing up into the property’s lower floors during heavy rainstorms or high water tables.
Frequently Asked Questions (FAQ)
#### What is a dual-pipe plumbing system in Dholera?
A dual-pipe system is a plumbing configuration that utilizes separate networks: one for potable municipal drinking water (blue pipes) and another for recycled greywater (green pipes) dedicated to flushing and landscape watering.
#### What is the minimum diameter of a toilet drainage pipe under DSIRDA GDCR?
The minimum internal diameter for all soil waste lines connected to water closets (toilets) is 100mm (4 inches).
#### Are grease traps mandatory for residential apartments in Dholera?
No. Grease traps are only mandatory for commercial kitchens, restaurants, and food courts where grease and oil discharges could block municipal sewer lines.
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