How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

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What is a drum trap at a plumbing drain?

Tuesday, July 2, 2019

A drum trap is one of several types of plumbing traps that were once acceptable, but now prohibited. The primary problem with a drum trap is that it is not “self-scouring,” per the requirement of Florida Plumbing Code (FPC-1002.2) and a similar citation in the International Plumbing Code (IPC). The drum shape creates pockets that will trap debris and grow bacteria. 

    Here’s a full list of prohibited traps from FPC-1002.3.

    The exception, which allows use of a drum trap for situations where a “solids interceptor” is needed, is helpful at a dental office so any crown, filling, or such can be retrieved from the drum if accidentally dropped down the drain. So the lack of a self-scouring property becomes an asset. The drum is openable for cleaning.

    The drum trap shown at the top of the page is a little unusual because it is a both a drum trap and an S-trap combined, and has what would be an excessive trap seal by today’s standards. The diagram above shows the more common type. But, if found in a residence today, a drum trap is an antique leftover from a bygone era.

    To learn about the bottle trap, another prohibited trap that looks similar but is a slightly different configuration, and often comes attached to a “designer European” sink fixture, see our blog post Why is the European-style bottle trap not approved by the plumbing codes in the U.S.? 

        For other prohibited trap designs, see our blog post What plumbing traps are illegal by code? Also, see our blog posts Can I make a trap under the sink from straight pipe and 90º elbows? 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 the vacuum breaker at my hose faucet leaking, gushing water, or making funny sounds?

What are the code requirements for plumbing vent terminations?

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

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? 

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 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.  

Photo - Ryan Fessler, Diagram - Carson Dunlop

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