How To Look At A House

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Why is there a flexible accordion pipe under the sink?

Sunday, August 19, 2018

Although the flexible, accordion-shaped pipe shown in the photo above is sold in home improvement and hardware stores, it is not approved for installation by plumbing codes, which require that any waste pipe fitting to be “self-scouring,” meaning that it should have a smooth interior surface that allows the free flow of drain water and prevents waste buildup on the pipe wall that leads to clogs. 

   Yes, you read that correctly. Although the stuff is allowed to be sold, it is not allowed to be used, and professional plumbers do not install it. The pipe should probably have a label on it like some of the merchandise sold in adult bookstores: “ADULT NOVELTY--NOT FOR ACTUAL USE.” 

   We typically see it used in a sink replacement by a homeowner or handyman that has trouble aligning the drain of the new sink with the U-shaped P-trap below it. A professional plumber can adjust the length of the trap arm (the pipe running from the trap to the wall) or add an angled fitting to turn the trap arm slightly to make everything line up. Also, there is an S-shaped pipe that can used as part of the tailpiece (pipe from the bottom of the sink to the trap) to get everything aligned.

  But the accordion-pipe is a quick and easy fix. Occasionally, we even see it used for a direct connection from the tailpiece to the trap arm, with the old P-trap pipe tossed in the trash. Because the standing water in the trap provides an important safety function of preventing sewer gas from rising up into the home through the sink, this is not a great idea.

    Also, corrugated flexible pipes have another problem. “Sometimes funky-smelling stuff can develop in the ribs,” according to James Freeman, a local plumber. “Because it’s above the trap, it can push smelly air into the room when you run the water.”

    Also, see our blog posts How can I tell what type of plumbing pipe I have? and If all the plumbing drains have water in them and you can still smell sewer gas, what's causing the 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? 

What is an "S-Trap" under my sink? Why is it a problem? 

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.  

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