DIY: Toilet Knocking Sound

Knocking sounds coming from the toilet are more than annoying; they can lead to serious problems if not quickly corrected. The pressure and sideways force of the water jostles the plumbing, which can eventually wear down the joints and fittings and loosen the straps that affix the pipes to the beams in the walls.

Sometimes, the knocking is coming from within the commode. A slight knocking sound may mean a part in the tank needs attention. If the toilet makes gurgling and soft tapping sounds, it could be the tank's flapper. A flapper that doesn't seal properly can allow water to continue to flow into the bowl, creating sounds like flushing or bumping in the night.

To replace a worn flapper, gather a small bucket, a new flapper and some old bath towels. Put on some work gloves that can help you get a grip on slippery parts. The water supply valve next to the wall should be turned off before working on the toilet. Slip joint pliers can help to loosen a tight water supply valve.

Remove the tank lid and scoop any water into the bucket to gain access to the flapper at the tank's bottom. Take off the flapper's chain from the tank's lever arm and pry the worn flapper from the tank's bottom with your fingers or pliers. Clean up any crud that has collected around the edges of the hole with a clean cloth. Place the new flapper chain onto the tank's lever arm and into the clips at the bottom of the tank. Allow the tank to fill.

A knocking sound that comes from deep in the walls more than likely means that the fill valve isn't working properly. When the toilet is flushed, the water fill valve opens to replace the water that has swished from the tank and bowl.

For the water to travel from the lines to your toilet, it requires pressure. The water fill valve keeps the water from flooding the home by staying closed until the toilet is flushed. As soon as the toilet's automatic water valve closes, the water stops. This is a lot of energy being stopped at once, which can cause the knocking. This loud bang or knocking sound is called a water hammer.

A water hammer arrestor allows the flow of water to release its energy through an air cushion and a piston after being suddenly stopped. An arrestor that fails allows water to get into the air cushion and gradually reduces that buffer in the water line.

The knocking sound can be eliminated by clearing the water from the arrestors. Turn off the water to the home at the main shutoff, usually located at the front of the house.

Open a faucet in the house's highest room and the lowest. Wait for the water to stop flowing from the faucets. Flush all of the toilets and run the dishwasher and washing machine to completely drain the lines of every last drop.

The arrestors that have been affected by water will be drained and the air cushion, or buffer, replaced. If this hasn't fixed the problem, you may need to call a professional to take care of the pipes that are knocking.