A plumbing trap is designed to always maintain a small pool of water that seals the drain pipe against sewer gas rising up into a home. But even a standard U-shaped trap tends to get clogged occasionally, and the slip fittings make it easy enough to open the trap an clear out a clog if necessary.

    Why invite trouble with a rectangular trap that is more resistant to water flow? The 90º elbows definitely fit the description of “shoulders” and “ledges” that are “capable of retarding or obstructing the flow of the piping" in the International Plumbing Code and the Florida Plumbing Code (1004.1) citation shown above. Also, traps are required to be “self scouring” at 1002.2, which this configuration is definitely not. So just don’t do it. 

    Also, see our blog posts Why is it a problem when a trap under a sink is installed backwards? and What is an "S-Trap" under my sink? Why is it a problem? 

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Here’s links to a collection of our other blog posts about PLUMBING:

• How can I protect my pipes to keep them from bursting during a hard winter freeze in North Florida?

• Why is there sand in the bottom of my toilet tank?  

• What causes a gurgling sound when a bathtub or sink drains? 

• Are drop-in toilet bowl cleaner tablets safe? 

• What can I add to my septic tank to help it work better?

• What are the code requirements for layout of drain piping under sinks? 

• Why is there mold inside my toilet tank?  

• What are the pros and cons of a wall-mounted toilet?

• Which plumbing fixtures require water shut off valves in a home? 

• How can I tell if a house is connected to a septic tank system or sewer?

• Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water? 

• Why is a backflow preventer required on lawn sprinkler systems? 

• How can I locate my septic tank? 

• Is a hot water faucet handle required to be on the left? 

• Can you live in a house while the plumbing is being replaced? 

• Why is the European-style bottle trap not approved by the plumbing codes in the U.S.? 

• Why can't PVC be used for water pipe inside a house? 

• What are the common problems to look for when the plumbing has been replaced in a house? 

• What's that powdery crust on the pipe connections at the water heater? 

• How can I tell what type of plumbing pipe I have? 

• What causes low water pressure in a house?

• Should I call a plumber or septic tank contractor when my septic tank backs up into the house? 

• How do I get rid of the sewer gas smell in my house?  

• What are the pipes on my roof? 

• Should I wrap the water heater with an insulation blanket? 

• My water bill went way up last month. How do I look for a leak?

• Why does the water have a rotten-egg smell in some empty houses? 

• Where is the septic tank? Are you going to inspect it? 

• What does polybutylene pipe look like? Why is it a problem?

• Which water pipes are an insurance problem and possibly uninsurable? 

• Does a home inspector check the plumbing under the floor slab?

• Is it alright to disconnect the washing machine drain from the septic tank and divert it to the ground in the yard?

      Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.