Every fixture shall have a trap; every trap shall have a vent.
Traps form a water seal between your home and the sewer system.
The “S” trap is used on older plumbing and often doesn’t have a vent pipe connected to it. The “P” trap is what we use today. (See Vent Pipes)
Traps can be made of different materials, some better than others. The chrome plated brass trap is used by most professional plumbers followed by the Schedule 40 PVC trap. Then there are the cheapo plastic traps.
Metal and Schedule 40 traps will last a good long time. The cheapo plastic trap will melt when hot spaghetti water is poured down the kitchen drain. They will melt and then come apart spilling the sinks’ water under the cabinet and onto the floor. Usually this event will wait until Thanksgiving Day when the family is waiting for dinner.
The Flexible Drain Line connector is something new in the market place. I cannot think of any self-respecting plumbing who would use such a device. Just looking at it would tell you of the germs, mold and bacteria that are caught on the inside of this device waiting to pollute your home. It is not acceptable on any code that I’m aware of. YIKES!
AVOID CHEAP - IT WILL COST YOU
Venting is an impressively important part of plumbing. Proper venting allows sewer gases to escape to the outside. Sewer gases (methane) are responsible for house explosions and are far more dangerous than natural gas used in cooking and heating.
Have you ever flushed the toilet and the bathtub goes “Glug Glug Glug”? It’s possible that the vent pipe is stopped up and the water draining from the toilet (3” trap) is siphoning the water out of the smaller trap (1-1/2” trap).
Using the right trap will maintain a water seal between the living space of your home and the sewer system and all its gases and other critters that live there.
When an “S” trap is installed and a full bowl of water is drained from the sink, a siphoning effect can occur causing the S-trap to drain itself with a “Glug Glug Glug”. This draining of the trap is why S-traps are no longer used in houses today.
The P-trap is connected directly to a vent pipe allowing the water to flow downward and the vent piping prevents the siphoning of the trap.