Repair Methods in Water Supply Pipes

Inspite of efforts put forth to maintain pipe lines periodically, the pipe lines sometimes are prone to damages like cracking and breaking due to various reasons.  The reason may be due to excessive water pressure, reduction of life due to exposure to unfavourable environment, breakage that may be caused while workmen dig out the trenches for doing some works in the vicinity of pipe line alignment, movement of heavy traffic, Excess over burden, etc.  The damages caused on account of the above factors calls for repairing of pipe lines within the shortest possible time limit. 

The efficiency of attending to the repair works to a great extent depend on the identification of the portion of pipe lines which is broken and which is causing water leaking profusely. Having identified the broken/punctured part, the next step involved is to get the damaged portion repaired as quickly as possible. The identifications of leaks is elaborately dealt in sub-section (Detecting leaks). We shall study the steps and method of repairing a broken down pipe line. 

Reaching Out to the Damaged Segment 

If the pipe is concealed in wall, chase out the portion of the wall to sufficient length so that enough working space is available. If the pipe line is laid underground, excavate earth along the alignment of the pipe line and expose the pipe. While excavating the trench, care shall be taken to ensure that no injury/damage is caused to any other portion of the pipe line. It may also be ensured that earth below the pipe lines is also not removed leaving long unsupported lengths. If the unsupported lengths of pipe line is very long, there is a possibility of undue deflection in the pipe causing yielding of joints which activate further leakages inviting more repairing problems. 

The problem is more critical for PVC pipes. If caving in of earth is likely to take place under the pipes, necessary supports shall be given to the pipes.  In case of loose soil, necessary shoring is to be made to avoid collapse of earth and falling on the pipe which may endanger the segment of pipe line which is not defective. In the case of pipes coming under the floor, the floor finish and other building element shall be removed carefully so as to cause least inconvenience and cost. 

Assessing the Nature of Damage 

Immediately after exposing the pipe line, the nature of damage, requirement of pipes, specials and other repairing materials and labour force required to complete the repair work within shortest duration, shall be assessed. These materials shall be procured and brought to site of work. 

Shutting Down the Water Supply 

The occupant of the companionship shall be informed about the defects in the pipe line and disruption of water supply during the repair period.  Before taking up the repair work, the water supply in this segment shall be shut down. If the repair is going to take much time, feasibility of providing some temporary bypass arrangements also can be thought of. Shutting down of water supply and taking up of the repair works shall be restricted to late night times, so that, inconvenience to the occupant is minimum. 

Repairing Damaged Portion of Pipe 

If the damage is significant, requiring replacement of pipes, the repairing shall be done as follows:

a) G.I. Pipes: If the damaged segment is in between GI unions, the same can be removed without much problem. The damaged pipe can be replaced with new ones with proper threading to accommodate the union and other specials. If there are no unions in between the damaged segment, the only way open to plumber is to cut the damaged portion and replace with new pipe. While cutting the pipe, fresh unions are also to be provided so that the length of new pipe replaced can be kept minimum.  The following precautions shall also be taken while replacing and jointing of new pipes in place of damaged ones. 

Pipes shall be cleaned and cleared of all foreign matter before being laid.  While jointing the pipes, pipes shall be oiled and rubbed over the white lead and few turns of spurn yam wrapped round the screwed end of pipe. The end shall then be screwed in the socket, tee, etc. with the pipe wrench.  Care should be taken that all pipes and fittings are properly jointed so as to make the joints completely water tight and pipes are kept at all times free from dust and dirt during jointing. Burr from the joints shall be removed after screwing. After laying, the open ends of the pipes shall be temporarily plugged to prevent access of water, soil or any other foreign matter. Any threads exposed after jointing shall be painted or in case of underground piping thickly coated with approved anti-corrosive paint to prevent corrosion. 

b)  PVC Pipe: In the case of PVC pipes, different types of jointing methods are adopted. While replacing the damaged segment, any of the accepted method of jointing may be adopted.  The accepted method of jointing are mentioned below: 

i) Solvent Welded Joints: These are permanent in nature and strong in tension. They are used for service pipes of water mains. These joints are commonly used and economical for PVC pipe works. 

This technique is used with both spigot and socket type joints, in which the socket is made specially to form a close fit on the pipe end and with injection moulded fittings. 

The solvent welded joint may be achieved either by neat  application method or by non-heat application method.  The non-heat application method is easier and is recommended for water supply installations. 

ii)  Flanged Joints: These are used for jointing of PVC pipes particularly of larger sizes to valves and vessels, and larger size metal pipes where strength in tension is required.  The joint is made by the compression of a gasket or a ring seal set in the face of the flange. The flange may be formed in several ways as under. 

By upsetting the pipe end on a mandrel after heating the pipe ends. A backing ring of metal or thermoses plastics compresses the upset pipe end on to the fitting face of the gasket.  Crinkles are formed too easily in the collar and the whole pipe loses much of its strength. 

By solvent cementing a plastic stub flange on to the pipe end and again using a backing ring.  The pipe end may also be welded to the PVC flange. 

By solvent cementing a plastic full faced flange on to the pipe end and bolting this to the fitting face. A backing ring or wide washer should be used to distribute the bolt loads.  This prevents the distortion of the PVC flange. 

iii)  Union Joint: This is a form of flanged joint in which the faces are held together by a screwed connection. A composite metal and PVC,socket union is a very satisfactory method of jointing PVC to screwed metallic fittings. 

iv)  Screwed Joints: These are similar to the joints used with metal pipes. If pipe has to be jointed by screw threads, only thick walled pipe should be used and cut with taper pipe threads. The-die should be clean and the thread pipes shall not be subjected to pressures exceeding two-thirds of the pressure rating for un- threaded pipes. 

c)  C.1. Pipe: Since CI pipes are used mainly in pumping  the repairing of CI pipes is not dealt elaborately.  But the principle involved in the repairing is same as that for GI pipe.  In this case, if the damaged pipes are with flanged end, the repair work  is very easy.  Just replace the damaged pipe and tighten the bolts of nuts after 

introducing 'the gaskets. If the pipes are with socket end, remove the original jointing materials by carefully chiseling it out and take out damaged pipe, introduce the new pipe and pack the joints with hemp yarn and molten lead. In the case of Tyson joints, rubber rings are to be replaced with new ones along with new pipe in place of damaged pipe. 

Repair of Sewer Lines and Trap 

The principle of repair involved is also same as that of water supply lines.  Additional precaution to be taken is to flush out the lines before taking up the repairs so that no excreta is left oil or accumulated in the pipe lines before removing the damaged segments. The flushing will avoid unhygienic environment during repair works.

Rectification of Leaking Taps

If a tap leaks up above the bonnet or cap instead of down the spot the cap is probably not screwed or tighl enough. Tighten the cap a triffle. If the let& still persists, the packing washer below the cap should he removed and replaced.