Method Statement Title: Installation & Testing of Underground Drainage Piping

Method Statement Title: Installation & Testing of Underground Drainage Piping

1.0       Scope

1.1       This method statement details the method for installation and hydrostatic testing of underground drainage piping.

2.0       Material

            2.1       UPVC Pipes to EN1401-1 (Formerly BS 4660) with push-fit grooved joints.

3.0       Applicable Location

            East and West Podium – Basement level.

4.0       Method

4.1       Storage  

• When off loading pipes shall be lowered to the ground either manually or with mechanical aid like crane depending on the quantity of the pipe and should not be dropped to the ground.  Refer – Manufacturer’s instruction for transport, handling and storage (Annexure – 1).

4.1.2    Pipes shall be given adequate support at all times and shall be stacked on a flat surface free from any sharp objects.

4.1.3    Timber supports of a least 3” wide shall be placed beneath the pipes with spacing not greater than 1.8 mtrs.   Closer supports will be required for sizes below 160mm.

4.1.4    Pipes shall not be stored under direct sunlight to avoid ultra violet degradation.

4.1.5    Socketed pipes shall be stacked in layers with sockets placed at alternate ends of the stack and with the sockets protruding to avoid unstable stacks and the possibility of imparting a permanent set to the pipes.

                        4.1.6    Larger pipe sizes of thicker class shall always be placed at the bottom.

            4.2       Preparation

4.2.1    The width of the trench at the crown of the pipe shall not be less than the outside diameter of pipe 300mm to allow proper compaction of side fill material.

                        4.2.2    The bedding shall consists of a free running granular material passing a 19mm sleeve, but with a minimum of fine particles.

4.2.3    The thickness of the prepared bed shall be at least 100mm.  It shall be well compacted and brought to an even surface so as to provide uniform support for the pipe.

                        4.2.4    Trenches shall be kept free of water by pumping the water out, if any.

            4.3       Installation

• Pipes are brought to the work place manually from the store to the hoist area and are shifted to the respective floors through the hoist.

• Ensure that the mating areas of spigot and socket are thoroughly clean and square.

                        4.3.3    Set the rubber ring into groove.

4.3.4    Assess the full socket depth by simple measurement and mark spigot accordingly.

                        4.3.5    Apply lubricant to the spigot side and to the inside of the joint on rubber.

                        4.3.6    Accurate axial alignment of the spigot and socket prior to jointing is important, hand feed spigot into rubber joint until resistance from the inner sealing section is felt.

                        4.3.7    Complete the joint by applying leverage to the following socket and using a timer block to prevent damage.

                        Important Notice

                        If pipes are cut on site, make sure that the new spigots are cut square with a fine toothed saw and are chamfered to half pipe thickness with a coarse file before jointing.

4.3.7    All pipes and fittings delivered to site for the work should be stored in an approved manner to avoid deterioration due to accidental damage and atmospheric condition.

                        4.3.8    Before final erection, all pipes should be free of dust, scale rust or other form of corrosion.

                        4.3.9    All pipes will be laid to a uniform slope as indicated on the drawing on a prepared trench bed.

                        4.3.10  Before laying, all pipes and fittings should be checked for defects and jointing spaces cleaned properly.

                        4.3.11  Socketed  pipes to be laid with sockets uphill.  Scoop out compact bed locally at pipe sockets where socket pipes are used.  Adjust pipes to line and level with the help of 1 mtr. Long spirit level and if required the surveyor’s help can be obtained. Ensure pipe bottoms rest uniformly on the bedding.

                        4.3.12  To avoid possible damage or deformation of the pipe, its support by the ground in which it is laid should be made as uniform as possible and must be free from large stones, sharp edged flints or other hard objects.

            4.4       Back-Filling

                        4.4.1    Before commencing to place any side fill material; any levelling pegs or temporary packing shall be removed.

                        4.4.2    Filling around the pipes shall be done with the same bedding material to a minimum height of 100mm and a maximum of 300mm and be throughly compacted.

                        4.4.3    Normal filling of trench shall then proceed in layers of 150mm with selected materials.

                        4.4.4    Plastic identification tape shall be installed during back filling operations.  The tape shall be centered on the pipeline with lettering facing upwards.

• Testing

• Air Testing

• The length of drain or sewer to be tested including any connections should be effectively plugged.

• Air is pumped into the test length by suitable means (eg., hand pump) until a pressure of 100mm of water is indicated on a manometer connected to the system.

• A suitable time should be allowed for stabilization of air temperature.

• The air pressure should not fall below 75mm of water during a period of five minutes, without further pumping.

• In case of unsatisfactory air test, hydrostatic test is to be followed so that the leakage can be assessed and located.

• Testing will be inspected by main Contractor / Consultant to their satisfaction and document for correct test will be maintained by getting approval in test certificate by Consultant and Main Contractor.

• Hydrostatic Testing

5.2.1    Water test is conducted to ensure and prove the tightness of the joints and ensure there are no leaks in the piping system.

5.2.2    The water pressure test can be applied to the system in its entirety or in sections.  All openings in the piping will be tightly closed by special cast iron pipe plugs or by another suitable means and the system filled with water to the point of overflow from the highest point.  The plugs can be temporally opened to make sure that all air has been vented and that water has reached all parts of the system.  

5.2.3    No section of the pipe shall be tested to less than 1.5 meter head of water.  In testing successive sections of piping, at least the upper 3 meters of the next proceeding section will the tested.  Except the upper most 3 meters, the whole system shall have been subjected to a height of less than 1.5 meter head of water.

5.2.4    The water shall be kept in the system or in the portion under test for at least 30 minutes before inspection starts.  While the system is under pressure, a careful inspection shall be made on all pipes and joints. If any leaks in joints or evidence of defective pipe or fittings is revealed, the defective pipe / fitting should be immediately replaced with new joints and materials. 

5.2.5    After the correction is made, the test pressure will be maintained for minimum 30 minutes and witnessed by ETA QA/QC Engineer. 

5.2.6    Testing will be inspected by main Contractor / Consultant to their satisfaction and document for correct test will be maintained by getting approval in test certificate by Consultant and Main Contractor.

5.2.7    Only after approval of testing back filling of trench will be allowed.

6.0       Records

            Prepare work inspection request (WIR) and have them signed by NMX/Consultant.

7.0       Attachments

            7.1       Test Format.