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Plug Drains to Keep Sewage Backup Out

If you live in an area prone to flooding or heavy rain, be prepared to plug your drains to prevent sewer backup.

Raw sewage can damage building components and carpeting, says Carl Pedersen, North Dakota State University Extension Service energy educator. Sewage also has high concentrations of bacteria, protozoans and other pathogens that can pose serious health risks.

Deciding if and when you should plug your drains depends on a variety of factors. For example, you should plug all drains in the lower levels of your home when local officials warn residents to do so or if you plan to evacuate because of the potential for flooding.

“Do not wait until flooding is imminent to try to obtain plugs because they may not be available, or you may have situations that need special attention in your home,” Pedersen says.

You may not need to plug drains because many new homes have anti-backflow or backwater check valves in the main sewer line that reduce the potential for sewage backup. While these valves are designed to stop backflow, some have failed, so you must decide if you want the added protection of plugging your drains.

Inspect your check valves annually to make sure they are free of debris and working properly. If your home has a backwater check valve, you usually can access it near the main sewage cleanout. If you have an older home, have a licensed contractor install a check valve.

Some homes may have slice valves. You generally can access slice valves through a holdout in the basement floor and turn them off and on easily in the event of flooding or sewage backup.

If you do not have a backwater or slice valve, you can install plugs in drains. Here are some plugs that might work for you:

  • Test ball: It’s used for pressure-testing plumbing systems but will work in an emergency to seal drains. Insert the ball into the drain pipe and inflate it with air to the prescribed air pressure. Once inflated, the ball will not allow water to flow in or out.
  • Twist plug: Insert it into the pipe and twist the wing nut until the plug is tight. Twist plugs come in a variety of sizes and work well with floor, shower and toilet drains.
  • Pressure plugs: These are conical-shaped rubber or wooden plugs. They’re smaller in diameter than the pipe to be plugged on one end and larger than the pipe on the other end. You force them into the pipe. You also may need to brace them to prevent pressure from pushing them out.
  • Threaded screw caps: You need to remove the plumbing fixture and insert the correct-sized cap in the pipe.

Plugs or threaded caps work best if you can remove the drain grates or other fixtures. If you can’t remove the grates, you can place a piece of inner tube that is larger than the drain hole on the area surrounding the drain and cover it with a piece of plywood or solid board to hold it in place. Particle board will not work because it can deteriorate and crumble when wet.

To hold the tubing and board in place, brace it against the ceiling. To avoid damaging the ceiling, place a 2- by 4-inch board or piece of plywood parallel to the ceiling. Then wedge a vertical 2- by 4-inch board between the board covering the inner tube and the board parallel to the ceiling.

Here is how to plug specific types of drains:

  • Toilet: Turn off the toilet’s water supply, remove the water line from the toilet and press the plunger to flush the toilet and empty the water tank. Then remove as much water as possible from the bowl by pouring a bucket of water into the bowl as fast as possible without spilling. Take out the two bolts holding the toilet and remove the toilet, then insert a plug in the drain.
  • Washing machines: Remove the drain hose from the washing machine and place the correct diameter plug in the drain pipe. The best option is a threaded-cap plug.
  • Sinks: Place a plug in the sink drain and overflow. The preferred method is removing the drain pipe from below the sink and placing a threaded cap on the drain outlet.
  • Bathtubs: If you have an access panel for the bathtub plumbing, remove the drain pipes and install drain plugs. If you don’t have access to the internal plumbing, use a twist plug in the drain. To plug the overflow, remove the overflow cover and install a drain plug that’s the correct size. You may need an automotive or marine plug because the overflow drain is shallow.
  • Showers: If you can remove the drain grate, place the proper-sized drain plug into the drain pipe and tighten it until it is snug. If you can’t remove the grate, cover the drain with a thick piece of rubber or inner tube and use the floor-drain bracing method.

“Before heading to the hardware store to buy plugs, remove floor grates or plumbing fixtures and measure the diameter of the pipe so you will know what size plugs you will need,” Pedersen says. “Each drain can be different, so do not assume your home has a standard size drain.”

For more information on plugging drains, visit, www.ag.ndsu.edu/pubs/ageng/structu/ae1476.pdf or view this video: www.ag.ndsu.edu/flood/plugging-home-drains-to-prevent-sewage-backup.

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