Homeowners may attempt to remove a clog in the sink drain and be inundated with water that gushes from the top of the sink trap or from the lower pipe that drains into the main drain in the floor.
This is because these pipes were installed without compression nuts to seal the openings in the event of a clogged drain. Compression nuts are cheap and easy to install with minimal effort and an adjustable wrench.
Why do these pipes overflow when a clog occurs?
Drain pipes work using gravity to move waste water downward and out of the main drain line. The drain pipe that extends from the sink to the "J" shaped sink trap beneath it may simply be inserted into the trap without a threaded connection.
The pipe that is connected to the lower end of the sink trap may also be inserted directly into the floor drain pipe without using a threaded connection.
Both of these setups are adequate when the waste water is flowing smoothly downward. They will also usually be sufficient if the drain line is clogged and filled with water.
However, when a plunger is used to try to unseat a clog, it creates pressure by forcing air into the pipes. If the clog is not displaced, the air forces the trapped water upward and out of the unconnected openings.
What is a compression nut?
A compression nut is a large plastic or metal nut with a rubber washer inside that is compressed to form a seal when the nut is tightened on these types of open drain pipe connections.
How can you add a compression nut to these connections?
You will need to buy 1 1/4" compression nuts for bathroom and 1 1/2" compression nuts for kitchen use.
Adding a compression nut to a sink trap
You'll need to remove the sink trap by loosening the threaded nut at the small end of the trap. Place a bucket under the trap before disconnecting it, because it will likely be filled with smelly water.
Turn the threaded nut counterclockwise while holding the trap upright. When the nut is completely loosened, slide the trap down from the drain pipe that extends from the sink. It's a good idea to clean out the trap while it is removed. You may even find a lost earring that became trapped after falling into the sink.
You will then slide the compression nut up the sink drain pipe, washer side down, and slide the top of the trap onto the pipe. Connect the other end of the trap by tightening the nut on the threaded connection.
When the threaded connection is secured, slide the compression nut down over the top rim of the sink trap. Tighten the compression nut with the adjustable wrench until it is snug.
You may be facing the same problem with the pipe that runs from the sink trap into the floor. This pipe will appear as an upside down letter "J", which the longer end extended into the floor connection.
Adding a compression nut at the floor will require the same procedure for removing the sink trap. Once the sink trap is disconnected, lift the pipe from the floor and slide a compression nut up the pipe, washer side down.
Push the pipe back down into the floor connection, and make sure that it is properly aligned to reconnect with the sink trap. You will then push the compression nut down the pipe to the lip of the floor connection, and tighten the compression nut until snug. Reconnect the sink trap and you're finished.
Contact local plumbing services for more help or info.