Pipe Installation

How to Install a Sewer Pipe

Pipe installation sould be done carefully with the adequate slope. No matter if the pipe is going to be installed inside of a structure or outside, the installation method will be the same. Depending on the sewer pipe material, things could be easier or more complicated, because the pipe will be harder to handle and the installation process of the sewer pipe will require additional labor and equipment.

To start, you must determine how far the pipe needs to go, and determine the elevation at which the pipe will be connected to the specific fixture or if it will be connected to another pipe. Another important information is to determine what will be the final installation height. Both, initial and final elevation must be measured at the interior point of the connecting pipe, just in the middle portion of the pipe.

Now that you have both elevations and the pipe length, we nee d to calculate the pitch or fall of the sewer pipe run. Subtract both elevation and divide the horizontal or pipe length into the difference in elevation, and that will be the drop per linear foot or meters of pipe. Be careful, a drop greater than ¼” per foot is not adequate as water will flow faster than solids, while a slope to small, less than 0.003, will be sufficient to carry solids away. The recommended pitch for 4" pipe is 1/8" to 1/4" per foot.

Start by opening the trench. Be careful once the trench is open and provide all safety measures to protect workers inside and outside the trench. Remove all loose dirt at the trench bottom and grade the trench bottom so the pipe could be installed over a smooth surface. Sometime you will need to place a bedding material to provide additional support to the sewer pipe, to reduce the possibility of ‘sag’ after the trench has been backfilled. The best material to use as bedding material is sand, but if unavailable then you can choose to place gravel bedding.

Once the select portion of trench has been prepared, lay the se wer pipe in the trench. It is recommended to start at the lower end of the pipe run, up to the higher elevation.

If the sewer pipes , has bell end; the bell end must be placed on the uphill side of the pipe run, reducing the possibility of leakage. Remember that before applying glue to the sewer PVC pipes, you must apply purple PVC primer. Purple PVC primer chemically cleans the PVC surface, so the glue acts properly. Insert the male end of the pipe into the female end and twist a little bit. To be sure that the pitch is being followed correctly, install a string along the pipe run. The string must be installed with the same slope as the pipe will be, but just one feet over the finished level. The measure from the string to the bottom of the trench will be the same along the entire run.

It is probable that the last portion of the run will need just a fraction of a pipe. Be aware that you will also need additional fittings to complete the installation. Once the pipe has been installed completely, check for any pipe that could be disconnected, broken or not installed properly. Now place the sand and/or gravel over the pipe, enough to cover at least 10” over the sewer pipe. Start compacting the material with a rammer or any other compaction equipment suitable for the type of pipe being installed. 

On long pipe runs, this process could be started once the pipe has been installed and while working on the next pipe segment. It is important to install a warning tape over the first layer of compacted soil, so others will be aware when excavating that a pipe is located under the detectable warning tape.

Source: http://construction.about.com