Michael Sweeney 
Your kitchen sink’s plumbing brings fresh water and transports waste, providing fresh drinking water while collecting refuse. However, its complex system may be hard to understand or troubleshoot when things don’t run smoothly.
To help you better comprehend the components of kitchen sink plumbing, we will break them down into their primary parts.
The P-trap
The P-trap is that U-shaped piece of pipe underneath your sink that serves two important purposes. First, it traps water to prevent sewer gases from seeping back up through your drain into your home; and secondly it acts as a catchall for anything you might accidentally drop down there (such as an earring!).
P-traps contain water within their curved part, connecting to a straight section that drains into the drain line through the wall and back out through a wall-based outlet. Slip-nut washers hold all pieces of the trap together.
Before servicing the P-trap, first shut off all water shutoff valves under the sink to prevent turning your kitchen into an indoor water park. Place a bucket underneath it to collect any sludge you may spill or lose during servicing, and loosen slip nuts holding it to drain line and tail pipe using channel-type pliers; be careful not to overtighten; tightened slip nuts may damage pipes if overdone.
The drainpipe
Your drainpipe carries wastewater from your sink directly to the sewer line, so keeping it full with water will prevent noxious sewer gasses from seeping into your home through its drainpipes.
Your sink’s trap, located at its base, acts as a seal that prevents sewage from rising up through your sink drain and entering. However, when this bend in pipe becomes dry food debris may clog it, leading to potential clogs in your system.
Drainpipes serve a dual function: providing fresh water to your sink and controlling its flow through a shut-off valve. Standing or discolored water around drain pipes indicates leaks or pipe damage, while gurgling noises could indicate improper slope or ventilation issues that require professional intervention to correct. Basic knowledge about kitchen sink plumbing will enable you to recognize such issues more quickly, helping you communicate more effectively with plumbers when issues arise.
The trap
Under your sink is a U- or S-shaped pipe which forms a water seal beneath your kitchen drain – this is known as a drain trap and plays an essential role in keeping hazardous sewer gas from coming back up into your home.
Food waste collected in your trap should remain contained and prevent it from clogging your sink drain, but if it dries out you could experience unpleasant and potentially toxic odors entering the living space.
As with other pipes in your kitchen, the trap beneath your sink may become clogged with food waste, grease and other debris over time. However, this should usually be an easy fix: use either a plunger or drain auger to break up and clear out clogs from your trap. However if this fails then professional plumbers may be needed – they’ll quickly identify the cause of any obstruction and quickly repair it.
The tailpiece
A drain trap is a U-shaped pipe designed to trap water to prevent sewer gases from seeping into your home and catch any objects that might fall down the sink’s drain, helping prevent clogs.
Under your sink is a drainpipe which connects directly with your home’s plumbing system via its trap. A tailpiece fits underneath your basket strainer and leads directly into a sink drain fitting or, in a two basin setup, directly into a tee fitting that receives waste pipe from both basins.
Apply a thick bead of plumber’s putty along the bottom edge of the sink-drain tailpiece using plumber’s putty. Slide a sink drain assembly onto it and tighten its slip nut with channel-type pliers or by hand; tighten or loosen by hand as necessary; make sure the trap bend fits onto a tee fitting, while its trap arm reaches down into your wall drain outlet for proper functioning.
