Code of practice for laying cast iron pipes
1994 Edition

IS 3114 approves several methods for joining cast iron pipes: cement joints primarily for gravity sewer systems using cement complying with IS 456:1978; flanged joints suitable for pressure pipelines or where dismantling is necessary, utilizing bolted flanges with gaskets to ensure tight seals; and proprietary flexible joints, which require prior authorization from the competent Authority and strict adherence to the manufacturer's guidelines. These methods guarantee robust, leak-resistant connections compliant with the standard.

According to IS 3114 (1994), trenches must be excavated to match the required alignment and depth, maintaining a minimum cover of 1.0 meter beneath roadways, adjustable based on local conditions with safety measures. Excavation should proceed only as permitted ahead of pipe laying. Trenches must be properly braced and drained to provide a safe working environment, with dewatering effluent directed to designated drainage channels or natural drains away from the site. In rocky terrain, trenches should be trimmed 150 mm below the pipe's barrel base and filled with granular material passing a 12.5 mm sieve, compacted adequately to create a firm pipe bed. These measures ensure proper pipe support and worker safety during installation.

IS 3114 specifies that excavated materials may be reused for backfilling if they meet Clause 8.2 requirements, typically suitable in non-critical settlement zones (Zone C) and consisting of loam, clay, sand, fine gravel, or other Authority-approved substances. For Zone A, backfilling should use sand, fine gravel, or similar granular material, placed in 150 mm thick layers and compacted by hand tamping, ensuring simultaneous filling on both sides of pipes and fittings to maintain alignment. In rocky or boulder-prone areas, trenches must be trimmed 150 mm below the pipe base and backfilled with granular material passing a 12.5 mm sieve, compacted fully to establish a firm foundation. Partial backfilling before testing requires explicit permission from the Authority.

Post-installation and backfilling, IS 3114 mandates conducting pressure and leakage tests on new pipes or valved sections. The pressure test is performed at a specified pressure, typically above the working pressure, after expelling air and filling the pipe with water, maintaining the pressure for a minimum duration of two hours. Simultaneously, a leakage test measures the volume of water needed to keep pressure within 0.035 N/mm² of the test pressure, indicating leakage levels. Acceptance requires that leakage does not exceed this threshold, with no visible leaks or unacceptable pressure drops. If criteria are unmet, repairs and retesting are necessary to ensure integrity and watertightness.

IS 3114 prescribes disinfecting new potable water mains to eliminate contamination sources such as soil, sewage, personnel, or equipment. The continuous feed method involves injecting a chlorine solution at 20–50 mg/l concentration into the main using hypochlorinators or solution feed chlorinators, filling it entirely with chlorinated water and maintaining contact for at least 24 hours. During this period, all valves and hydrants should be operated to ensure thorough disinfection. The residual chlorine must remain at or above 10 mg/l after 24 hours. Subsequently, chlorinated water is flushed until chlorine levels match normal system concentrations, followed by mandatory bacteriological testing. If tests fail, the disinfection process must be repeated before the main is commissioned.