Northern Pipe Products Inc. gasketed PVC pipe has a factory-installed rubber ring joint. This locked-in-place design prevents fishmouthing or accidental dislocation of the sealing gasket when pipe spigots are inserted in the bell joint. Do not attempt to remove the gasket from the gasket groove. The pipe-coupling gasket should be carefully inspected and cleaned to insure that no dirt or foreign matter is between the gasket and the pipe. After the pipe is placed in the trench the coupling should again be inspected to confirm that no dirt is in the gasket groove area. Pipe lubricant should be placed on the gasket face and on the spigot end of the pipe to the insertion line. Make certain the pipe end is supported off the ground so the lubricant does not pick up dirt. The pipe then should be inserted into the bell, aligned, and carefully pushed past the gasket. The spigot insertion mark is a “reference mark” to indicate the proper depth of insertion. In a properly assembled pipe-to-pipe joint, the insertion mark is flush with the lip of the adjoining bell. Care must be taken to insure that the spigot is not over-inserted. Use extreme care when assembling gasketed pipe with bar and block method or a machine such as a backhoe to prevent joint misalignment or over-insertion. Do not swing or stab the joint together. If the pipe does not go into the bell to the insertion mark, this may be an indication of a pushed gasket. A feeler gauge can be used to determine the position of the gasket in the coupling. If pipe assembly is at the trench side and then lowered, the same procedure is followed. As the pipe is lowered into the trench, holding pressure should be exerted on the end of the pipe, thus preventing movement in the bell after insertion. The pipe should be inspected to insure no lessening of insertion depth has occurred. Usually pipe larger than 8″ diameter is assembled in the trench. Field cutting the pipe may be necessary. Square cuts are essential. Northern Pipe Products Inc. recommends the use of a wheel type cutter and a mechanical beveler to complete the cutting procedure. After the cut is made, the pipe should be beveled smoothly to the original degree of the factory bevel. Fittings are usually gasketed slip joint fittings manufactured from PVC. Care must be taken to avoid rolling or cutting the fitting gasket. The same lubrication procedure used on the pipe is recommended for placement of the fitting.

Solvent welding or cementing pipe joints may be selected as an alternate method of installation. Although the pipe is of the same material as that with a gasket joint, the method of connecting the pipe is quite different. Clean and dry the spigot and bell socket of all dirt, moisture, and grease. Using a clean brush or applicator, coat the inside of the socket with cleaner solvent. Avoid puddles or amounts of standing solvent in the coupling. Apply a coat of cleaner solvent to the spigot end of the pipe. Apply the filler solvent cement to the spigot end of the pipe ONLY. Rebrush the bell socket quickly with cleaner solvent. Push the spigot into the socket, turn 1/8 to 1/4 turn pushing the pipe completely into the bell socket making sure the spigot bottoms out at the full socket depth. Hold firmly until the joint is set up (usually a matter of seconds). As the pipe is joined, a bead of solvent should appear at the outside edge of the socket. Wipe off the excess solvent with a clean rag or paper towel. Final setup and curing time varies depending on pipe size, temperature, and humidity. Longer setup time is necessary in colder weather. More care is needed to be sure the welding solvent has cut into the pipe. Allow at least 24 hours before testing the joint. More workers may be needed to handle larger diameter solvent welding. In sizes above 6″ diameter, three workers are typically used, two to make the solvent joint and one to insert and turn the pipe.

A square cut is essential when making a field cut of PVC pipe. PVC pipe can be easily cut with a fine tooth hacksaw or a handsaw. Power type saws with steel blades or abrasive discs can also be used. It is recommended that the pipe be marked around its entire circumference prior to cutting to assure a square cut.

After a pipe is field cut, assure that the pipe is beveled. Use a factory finished beveled end as a guide to determine the angle and the length of the taper. The end may be beveled using a plastic pipe beveling tool, a course file or rasp, or the abrasive disc power tool that was used to cut the pipe.

Proper compacting of the bedding material in the haunching area is the most important criteria to limit the deflection of a flexible PVC pipe. Embedment material should be placed and consolidated under the pipe haunch area and through the initial backfill area to provide adequate side support to the pipe while avoiding both vertical and lateral displacement of the pipe from proper alignment. Initial backfill is that portion of the pipe embedment beginning at the springline of the pipe and extending over the top of the pipe. This area should also be properly compacted to aid in limiting pipe deflection. Embedment materials suitable for proper compaction shall be used in the entire embedment zone.

In large water projects such as rural water and irrigation systems, both gasketed pipe joints and solvent cemented joints are quite common. Use of a plow, trencher, or backhoe may be used in pipe placement. Some pipe may be placed through a plow chute or from the top of the ground behind the trencher or backhoe. In all cases, care must be taken not to exceed the recommended curvature limits for the pipe or serious pipe stress and breakage could occur.

The response of PVC pipe to longitudinal bending is considered a significant advantage of PVC pipe in buried applications. PVC pipe may be deliberately curved during the installation operation to make a change in alignment and grade, or to make a change in direction. The shortest longitudinal bending radius allowed for PVC pipe is equal to 300 times the pipe’s outside diameter.

Most sewer projects do not allow for bends and curves but rather a straight line and grade from manhole to manhole. As with pressure pipe, Northern Pipe Products Inc. PVC sewer pipe may also be curved to allow for bending in the trenching operation to make a change in alignment and grade, or to make a gradual change in direction.

The next charts define the minimum radius of curvature and the maximum recommended offset per length of pipe.

In large water projects such as rural water and irrigation systems, both gasketed pipe joints and solvent cemented joints are quite common. Use of a plow, trencher, or backhoe may be used in pipe placement. Some pipe may be placed through a plow chute or from the top of the ground behind the trencher or backhoe. In all cases, care must be taken not to exceed the recommended curvature limits for the pipe or serious pipe stress and breakage could occur.

The response of PVC pipe to longitudinal bending is considered a significant advantage of PVC pipe in buried applications. PVC pipe may be deliberately curved during the installation operation to make a change in alignment and grade, or to make a change in direction. The shortest longitudinal bending radius allowed for PVC pipe is equal to 300 times the pipe’s outside diameter.

Most sewer projects do not allow for bends and curves but rather a straight line and grade from manhole to manhole. As with pressure pipe, Northern Pipe Products Inc. PVC sewer pipe may also be curved to allow for bending in the trenching operation to make a change in alignment and grade, or to make a gradual change in direction.

The next charts define the minimum radius of curvature and the maximum recommended offset per length of pipe.

Backfilling varies according to project specifications. There are several practices common to all backfilling. PVC pipe must be installed with proper bedding to provide support under the pipe. Initial backfilling should be completed as soon as possible after the pipe is laid because this will protect the pipe from shifting due to cave-ins. Material immediately surrounding the pipe should not exceed 3/4″ size. All voids under and around the sides of the pipe should be hand filled and compacted. If joints are to be left open for inspection during testing, the center section of the pipe must be covered and compacted to eliminate movement of the pipe when pressurized. If backfill material is put over the pipe in lifts and mechanically compacted, extreme care must be used not to fracture the pipe. Never use a hydrohammer compactor directly over the pipe until at least 30″ of backfill material has been placed. All backfill material should be void of rock, frozen chunks and debris.

The pipe line should be filled as slowly as possible (not more than 1 ft/sec) to avoid any unnecessary surges. Venting air from the line during filling is of major importance.

The line can be filled from any available water source. The water can be introduced from lines already in service through valved connections.

Northern Pipe Products Inc. recommends filling the new pipeline from the lowest point in the line. Where a portion of pipe is to be tested but has not yet been tied to the final source, another source of water must be found.

To avoid water hammer during the filling process, always fill the line slowly. Avoid high water velocities because the resulting water hammer could cause pipe failure.

Air needs to be vented out of the filled line at all high spots while filling and before making pressure and leakage tests. Automatic air release valves are recommended.

The testing procedures and requirements are usually stated in the project specifications. The following are Northern Pipe Products Inc. recommendations for testing PVC pressure pipe:

1. The testing connection location should be at the lowest point of the line to be tested.
2. Be sure all blocking is in place (if concrete is used it must be cured to the necessary strength to withstand the pressure).
3. Pipe must be back-filled properly before testing.
4. The ends must be capped and blocked.
5. Absolutely do not use air pressure for testing. Only hydrostatic testing is recommended.
6. Flush lines thoroughly to remove as much existing air as possible. If air pockets remain, it will be very difficult to complete testing.
7. Pipe should not be tested beyond 100% of the pressure rating of the pipe.
8. The leakage allowance can be calculated from the chart on the next page.
9. If the quantity of pipe to be tested is large, the test should be done in sections.
10. If the pipe is to be tested before it is tied to a final water source, an alternate water source may be needed. The quantity of water to fill the line can be determined from the chart on the next page.

The testing requirements for testing PVC sewer pipe are stated in the project specifications. Each Engineer will specify the type of tests required. The test could vary from a ball and cleaning test, a visual test, a leakage test, a low-pressure air test, infiltration or exfiltration test, or a pipe deflection test. Each test has its own specific methods. Testing is generally done between two consecutive manholes.

When testing, it is very important to make sure that the lines are clean. The ball test will usually accomplish this by flushing an appropriate size cleaning ball through the line.

Simple visual lamping with mirrors and lights can be used for visual tests, or a closed circuit television can also be used.

Leakage tests, whether for air or water leakage, may be taken. It is extremely important that all branch connections be capped and secured before this type of test is attempted. Air testing sewer line can be done with very low pressure. At no time should the air pressure exceed 9 PSI.

When using infiltration and exfiltration testing, generally applied requirements show that leakage should not exceed fifty gallons per inch of external pipe diameter per mile of pipe per day. Other requirements regarding level of water must be met to accomplish this kind of testing.

In deflection testing, the maximum allowable pipe deflection (which is reducing the vertical inside diameter) is 7.5%.

Proper placement and compaction of the backfill material in the embedment zone of the pipe in the installation process is the key to maintaining minimum deflection.

Deflection tests are taken with a proper size mandrel or sewer ball that is put through the pipe on a go or no-go basis. Again it must be emphasized that to ensure accurate testing, the lines must be thoroughly cleaned previous to testing.

Other specific testing details may be found in the ASTM D2321 Specification on the Standard Recommended Practice for Underground Installations of PVC Sewer Pipe, or in the PVC pipe installation chapter of the Handbook of PVC Pipe Design and Construction Manual published by the Uni-Bell Plastic Pipe Association.

Service lines running from the main sewer line to the unit being serviced are installed in the same manner as the main line using proper installation procedures. If main line full wyes have been installed, put the correct bend into the outlet of the wye and lay the service line to the unit, making the connection at that point.

It is extremely important when making the connection to the main that proper bedding and compaction is done at the point of connection to prevent any movement, collapse, or deflection. If the full wye has not been installed in the line, a saddle type wye must be installed on the pipe to gain entry for the service line. Care must be exercised when preparing the main line for this saddle. The saddle wye has a unique centering ring feature. A template is provided which is placed on the main line and a hole cut to the exact size. When the hole is completed, use care to clean, making sure that no rough edges remain. Stainless steel galvanized straps should be used to secure the wye in position after the solvent has been applied to the saddle and the pipe.The fitting or bend needed to make the correct position of the service line can then be placed and the service line laid to the unit. The same method of carefully trenching, placing, and backfilling done on the main lines should be in practice on the service lines.

Care must be taken not to drag PVC pipe on the ground and cause wear on the pipe or to the spigot. Any excessively rough handling of the pipe can lead to leaks and breaks when the system is activated and pressurized.

Refer to OSHA standards regarding current safety regulations pertaining to excavation. The trench shall be sloped, supported, or drained when necessary so that the workers can work safely. The trench depth should be at least 6″ below the deepest frost penetration.

The trench width at the ground surface may vary with and depend upon the depth and the type of soils. The minimum clear width of the trench measured at the springline of the pipe should be at least one foot greater than the outside diameter of the pipe to enable backfill material to be installed in the haunching area. If this trench width is exceeded, pipe zone haunching should be compacted to a point of at least 3 pipe diameters from the pipe on both sides of the pipe or to the trench walls, whichever is less.

Regardless of the type of excavating equipment used, the trench bottom should be smooth and free from rocks, dirt clods, and frozen material. If the trench bottom is hard, a 4″ layer of soft granular material should be spread evenly along the bottom of the trench.