Express Plumbing Heating & Air Blog

Many sinks are built into cabinets. It’s such a great idea, more storage space for all your stuff. Well, that’s what you think until you open the doors and see that curved pipe hanging out right in the middle of all that storage space. What’s that u-shaped pipe all about and why is it taking up valuable storage space? A P-trap.

Its purpose is to stop the sewage gases from drifting from the drainpipe into your home or building. While at first glance this pipe looks like a U, if you include the pipe that connects to the drainpipe and tilts your head (or turn the pipe on its end) there it is, it does look like a P.

In the plumbing systems in our houses or buildings. All wastewater and any accompanying waste go down the drain. Since water is not flowing through this system constantly it can get a little dry in the pipes. Causing waste to decompose. So with decomposition gases form. These gases are considered sewage gases which not only smell like what we associate with the odor of sewage but also include gases that can be detrimental to health in highly concentrated doses.

These gases want to escape from the pipe. So the plumbing system provides a vent in the roof that these gases can escape from. They also try to come back up through the pipes attached to our drains if it wasn’t for the p-trap. P-traps are located at every open drain in your house or building, meaning they can connect to all sinks, showers, toilets, and drains.

The p-traps water in its dip, sealing off the pipe. As water flows down the drain. The water level rises and flows down the drainpipe with accompanying waste to the sewage system. As the water stops flowing. The water balances out and new water becomes trapped again in the dip of the p-trap. This water eliminates space for any air or gases to flow back up through the drain. Water ion the main factor that allows a p-trap to work. If the p-trap becomes dry. Then those smells can start to seep into your building. They typically only become dry at drains that are rarely used. Most often floor drains. If you begin to smell an odor from a drain. Pour some water down it to till the p-trap back up.

For the most part, waste is able to move through the p-trap pretty successfully. It is built to create a smooth flow and there is typically enough water to create a consistent flow. Some things can begin to build up over time, however. Causing a cog in the drain. Changing or cleaning the trap will fix the problem.

Brad Jordan

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