Tree roots are often the cause of damaged underground sewer pipes. When repairing sewer pipes, finding the exact location to patch can be tricky. Use a sewer inspection camera to help, or hire a professional to save time and money. Dig the trench a little deeper than the actual pipe section you'll repair, especially if you are dealing with concrete pipe (see Warning). Rent the appropriate cutting tool to remove the damaged section: For concrete, use an angle grinder with a diamond circular blade; for cast iron, use a power hacksaw or cast iron chain cutter; for plastic, use a reciprocating saw or handsaw. You can repair any sewer line using PVC.
- Skill level:
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Things you need
- Pipe (typically PVC)
- Flexible rubber sewer joint coupling (w/stainless steel clamps/bands)
- Calibrated torque wrench
- Eye goggles
- Bevelling tool (metal file or similar)
- Pipe joint lubricant
- Cutting tools
Select your replacement pipe material (typically PVC). Cast iron is considered quite durable, quiet behind walls and has been used for centuries. Clay is not as durable, but its use dates back to 4000BC and it can last 100+ years, provided there are no faulty couplings. Cement pipe is used a lot and considered historically dependable. Plastic pipe is considered to have the same longevity as clay, is the most economical and easy to assemble. It's lightweight, easy to handle, will not corrode and is often the replacement pipe of choice (PVC generally preferred over ABS).
Decide whether to use a rubber gasket or fitted couplings with glue. (This article focuses on rubber gaskets.)
Measure the diameter of the pipe you need to replace (4" to 6" diameter is typical). Purchase the appropriate size of coupling with stainless steel clamps. If necessary, purchase adaptor coupling to join pipes of different diameters.
Drain the sewer pipeline by shutting off the water main to the house, flushing all the toilets and turning on all faucets. This will empty the sewer system of effluents (aka wastewater).
Make sure the upper section of the pipe is supported before cutting damaged section away. Put on eye goggles, face mask and gloves for protection from flying debris. Place a bucket beneath the cutting area to catch any residual wastewater (aka effluent) that may remain in the lines. Cut the damaged section of pipe out carefully using the appropriate tool, and round off any sharp edges with a bevelling tool, if necessary.
Clean all the contact surfaces of the joints. Consider laying thin plastic sheeting under your work area to keep out dirt. Lubricate the gasket/coupling and pipe ends with soapy water or an approved lubricant for your rubber coupling just prior to assembling. If dirt or debris attaches to lubricated surface, clean and repeat.
Loosen gasket clamps and apply steady pressure as you slide coupling at least two to three inches straight over pipe ends you are repairing. Do not over-insert.
Tighten clamps/bands alternately using your torque wrench set to 60 in./lbs.
Run sewer effluent water through the patched pipe to test for leaks before backfilling the hole.
Tips and warnings
- Consider installing a cleanout where you've cut the line.
- Use household vegetable oil or shortening if you don't have pipe lubricant.
- Consider trenchless sewer line replacement if the sewer pipe needing replacement is under a concrete driveway, house, or other difficult-to-reach location.
- Know your soil type for trenching and selecting the best pipe material in accordance with local regulations.
- If you have a small hole to patch, consider Fernco's "Pow-R Patch" or one of their other quick repair pipe products.
- Wear goggles, gloves and a dust mask when cutting into the pipe.
- This article is not meant to replace the advice of a certified professional plumber.
- Research and adhere to all federal, state and local safety codes, building codes and regulations.
- Temperature changes affect pipe material.
- Sidewall trench cave-ins/collapses can occur. Qualified professionals should be used. Use precautions with safety shoring box when trenching on a slope, and/or sheeting for trench wall support.
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