IS 15778:2023 is the Indian Standard (BIS) for chlorinated polyvinyl chloride (cpvc) pipes for potable water supply - specification. This standard specifies the requirements, test methods, and marking for Chlorinated Polyvinyl Chloride (CPVC) pipes intended for hot and cold potable water supplies. It covers material properties, pipe dimensions for different pressure ratings (SDR 11 and SDR 13.5), and physical, mechanical, and thermal characteristics to ensure safety and performance.
Specifies requirements for CPVC pipes suitable for hot and cold potable water distribution systems.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
IS 15778 is the specification for Chlorinated Polyvinyl Chloride (CPVC) pipes for potable water supply (hot and cold). CPVC handles continuous service up to 93 °C — versus uPVC (IS 4985:2021) limited to 45 °C continuous. This makes CPVC the standard material for hot-water plumbing in modern Indian buildings.
Use IS 15778 CPVC pipe when: - Geyser hot-water supply lines - Solar hot-water loops (collector to tank to fixtures) - Combined hot + cold water supply within a single building - Industrial hot fluid handling (compatible chemistry, ≤ 93 °C, ≤ 16 bar) - Hospital and laboratory hot/cold lines
CPVC has eclipsed copper as the default hot-water material in mid-rise residential and commercial in India over the last 15 years — lower cost, easier site joining (solvent cement), no scale formation, no electrolytic corrosion. The 2023 revision tightens dimensional tolerances and aligns with newer ASTM equivalents.
CPVC's value vs uPVC is its temperature tolerance. The design pressure de-rates as service temperature rises:
| Service temp | De-rating factor | PN 10 effective pressure | PN 16 effective pressure | |---|---|---|---| | 27 °C | 1.00 | 10 bar | 16 bar | | 40 °C | 0.83 | 8.3 bar | 13.3 bar | | 50 °C | 0.71 | 7.1 bar | 11.4 bar | | 60 °C | 0.62 | 6.2 bar | 9.9 bar | | 71 °C | 0.50 | 5.0 bar | 8.0 bar | | 82 °C | 0.40 | 4.0 bar | 6.4 bar | | 93 °C (max) | 0.33 | 3.3 bar | 5.3 bar |
Geyser deliveries typically peak at 60-65 °C. For domestic geyser plumbing, PN 10 CPVC at 60 °C gives 6.2 bar working — well above any building-services demand. Use PN 16 if you anticipate water-hammer, multi-storey high-pressure systems, or industrial use.
Vicat softening temperature: ≥ 110 °C (vs ≥ 80 °C for uPVC).
Two dimension series are available; check supplier datasheet for which one your fittings are compatible with.
SDR 11 series (CTS — Copper Tube Size): - Common in domestic plumbing - Sizes 12 mm to 50 mm CTS (nominally matches copper tube OD) - Wall thickness designed for SDR 11 (OD/wall = 11) → PN 27 cold, PN 9 at 82 °C - Standard sizes: 1/2", 3/4", 1", 1-1/4", 1-1/2", 2" CTS
IPS series (Iron Pipe Size — schedule 40 / 80): - Used in industrial and large-diameter applications - Sizes 1/2" to 12" IPS - Schedule 40 (lighter wall) and Schedule 80 (heavier wall) available
Standard pipe length: 3 m or 6 m (typically supplied in 3 m for domestic CTS, 6 m for IPS).
Hydrostatic pressure test (key acceptance): - 1 hour at 27 °C, hoop stress ≥ 50 MPa — pipe must not burst - 1000 hour at 27 °C, hoop stress ≥ 27 MPa — long-term verification - 1000 hour at 82 °C, hoop stress ≥ 11 MPa — high-temperature long-term verification (the headline test that distinguishes CPVC from uPVC)
Vicat softening temperature: ≥ 110 °C
Density: 1.50-1.55 g/cm³ (CPVC is denser than uPVC due to chlorine content)
Falling-weight impact test: at 0 °C, must not crack at specified drop height (size-dependent)
Reversion test: length change ≤ 5 % when heated to 150 °C (residual stress check)
Migration test (potable water): - Lead: ≤ 0.01 mg/L (CPVC formulations now use organotin or calcium-zinc stabilisers, lead-free) - Cadmium: ≤ 0.005 mg/L - Total organic carbon (TOC): per BIS Annex (low — no taste/odour transfer)
Marking on pipe (every 1 m): - IS 15778:2023 - Manufacturer name / trademark - Nominal size (e.g., `1/2" CTS SDR 11`) - Pressure rating at temperature (e.g., `100 psi at 180 °F` is common US-style marking) - BIS licence number
1. CPVC fittings on uPVC pipe (or vice versa). Despite similar appearance, the formulations and dimension series differ. Mixing causes joint leaks at temperature cycling. Always match pipe and fittings to the same standard (and ideally same manufacturer). 2. Wrong solvent cement. CPVC needs CPVC-specific solvent cement (orange or yellow body) — uPVC solvent cement (grey/blue) doesn't bond CPVC reliably under hot-water service. Read the cement can. 3. Joint cure time before hot-water flow. CPVC joints reach handling strength in 30 min cold but need 24 hours before exposure to ≥ 60 °C water. Premature heat exposure peels the joint apart. 4. Inadequate hanger / support spacing for hot-water lines. CPVC creeps at temperature. Manufacturer support-spacing tables must be followed (typical: 0.5 m for 1/2" CTS at 60 °C horizontal). Skipping hangers = sagging pipe + joint stress. 5. Direct copper-to-CPVC compression fittings without dielectric isolation in mixed systems. Galvanic + thermal cycling stresses the joint; use threaded transition adapters (CPVC male thread + brass female). 6. CPVC buried directly in concrete slab without sleeve. Concrete cure exotherm + alkalinity can affect CPVC long-term; always sleeve in PVC conduit before slab embedment. 7. UV exposure for exposed pipes. Like uPVC, standard CPVC degrades in direct sun (slower than uPVC due to chlorine, but real). Specify UV-stabilised grade for exposed runs or wrap in foam-rubber + foil insulation. 8. Mixing CPVC with PEX-only fittings. Some 'universal' fittings are PEX-only and don't seal against CPVC OD tolerances. Match the system. 9. Bending CPVC by heat-application. CPVC must be cold-routed (no field heating). Use elbows for direction changes.
Standard hot-water + cold-water building design cascade: 1. Demand and load (CPHEEO tables) — domestic + hot-water mixing fraction. 2. Hot-water source — geyser (electric / gas) at each fixture group, OR central solar-hot loop (more common in commercial / hostel). 3. Pipe routing: - Cold rising main + branches: IS 4985 uPVC PN 6-10 - Hot risers (geyser to mixing valves): IS 15778 CPVC PN 10 / SDR 11 - Recirculation loop (large buildings): IS 15778 CPVC PN 10 + insulation 4. Sizing (Hazen-Williams or Darcy-Weisbach with hot-water density correction). 5. Pressure class — typical PN 10 CPVC handles all building services up to 8-10 floors with booster. 6. BOQ language: `CPVC pipe per IS 15778:2023 SDR 11, ISI marked, [size] CTS, [length] m, with manufacturer's CPVC solvent cement and CPVC-compatible fittings; UV-stabilised grade for exposed sections.` 7. Insulation: 13 mm closed-cell elastomer (NBR/EPDM) on hot lines for energy efficiency and condensation control on cold lines. 8. Site QA: ISI mark + manufacturer name + size + SDR visible on every length; pressure-test the system at 1.5× design pressure for 30 minutes before close-out, hot circulation test before handover.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Base Material Classification | CPVC compound conforming to Class 23447 of ASTM D1784 | CPVC compound conforming to Class 23447 of ASTM D1784 | ASTM D2846/D2846M |
| Vicat Softening Temperature (Min) | 110 °C | 110 °C (Requirement for cell class '7' in 23447) | ASTM D1784 (referenced by ASTM D2846) |
| Common Dimension Ratios | SDR 11 and SDR 13.5 | SDR 11 and SDR 13.5 | ASTM D2846/D2846M |
| Flattening Test Requirement | No cracking when flattened to 40% of OD | No evidence of splitting, cracking, or breaking when flattened to 40% of OD | ASTM D2846/D2846M |
| Minimum Burst Pressure (SDR 11 Pipe at ~23-27°C) | 5.86 MPa (at 27°C for 22 mm OD pipe) | 850 psi / 5.86 MPa (at 73°F / 23°C for 1/2 in pipe) | ASTM D2846/D2846M |
| Sustained Pressure Test (Hot) | 1000 h at 82°C with hoop stress of 6.89 MPa | 1000 h at 180°F (82°C) with hoop stress of 1000 psi (6.9 MPa) | ASTM D2846/D2846M |
| Opacity Requirement for Potable Water | Pipe shall be opaque; light transmittance shall not exceed 0.2% | Required for potable water applications, often verified through NSF/ANSI 61 certification | NSF/ANSI/CAN 61 |