Laying Sewer Pipe

They aren’t always fun to talk or think about but sewer pipes are an important part of any community’s water system, and it’s even more important they are installed and run properly to avoid backups into houses, drinking water or fresh waterways. When laying a new sewer pipe it’s vital to follow the appropriate steps, so here are the steps to follow in order to ensure the pipe is installed correctly and will not cause any issues in the surrounding community.

Determine Elevation

First things first: you have to know how far this sewer pipe is going, whether it’s connected to any specific fixtures or other extending pipes and, most importantly, the installation height. The general guideline is that sewage should run downhill and away from communities so you need to know the initial and final elevation, measured at the interior point of the connecting pipe. This can be done using a laser level, GPS or regular surveying equipment.

Slope

With the elevation and the pipe length known you will then need to figure out the pitch, or fall, of the sewer pipe. To do this, subtract both elevations and divide the horizontal pipe length into the difference in elevation. This gives you the drop per foot or meter of pipe. Something to keep in mind is that if the drop is greater than ¼” per foot won’t work while a slope that’s too small (less than 0.003” per foot) will not be adequate either. Ideally, for 4” piping, a 1/8” to ¼” per foot is recommended.

 Trenching & Bedding

You will need to dig a trench to lay the pipe itself in. Make sure you are following all safety procedures for workers completing the trench. It is recommended to grade the trench, and remove all loose dirt, so that the pipe is installed on a smooth service. You might have to use some bedding to provide the required support for the pipe being installed. The best bedding material to use is sand, but gravel is a close second should sand not be available to you. Make sure the bedding you do end up using doesn’t contain any sharp stones as these could puncture, or wear away at, the pipe and cause issues or require a replacement pipe prematurely.

Laying the Pipe

Once the area has been properly prepared it is time to lay the pipe. Usually it is recommended to start at the bottom and work your way up to the higher elevation. If the pipe has a bell end on it then the bell must be placed on the uphill side so as to reduce the possibility of leakage. Also, make sure to apply the PVC primer before applying any PVC glue.

Final Section

It is very possible that the last section of the run will only need a portion of a full pipe, but it’s important to know that you will also need other fittings to complete the pipe installation. Once the installation is complete, you should check along the run to make sure none of the previously installed pipes are leaking, cracked or otherwise damaged potentially from the installation.

If there aren’t any damages or leaks you can start covering the pipes with sand or gravel (as you used in your bedding material) making sure you cover the pipe by at least 10” with this material. Then the ground can be compacted – as appropriate for this kind of piping – and soil can be added on top. It is also important to put a warning tape just over the first layer of soil so that if this area needs to be excavated in the future others will be aware that there’s a pipe underneath.

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