So my father-in-law and I are going back and forth..

I plan on redoing my entire main plumbing. When I purchased the house we remodeled the bathroom and had a plumber run a new schedule 40 stack and used a firmco to tie into the existing terracotta.

Due to snaking my lines every 90 days my plan is dig up the basement and remove all the terracotta, replacing it with schedule 40. There is currently a terracotta p-trap right before the line exists the house.

My understanding is that if all the appliances (floor drain, sinks, toilet and the washer and dryer) are trapped, then there would be no need to trap the entire line right before it exits the house. When I tell him I plan on removing that P-Trap and straight piping it directly out of the house, he looks at me like I’m crazy.

He is no plumber nor am I. But I plan on doing this in house rather than paying a company to do a trench less repair (which might not solve the issue) when I can save $2,000 by using a little man power.

So... who is correct ?

-Father-In-law says trap it -I say no trap

  • You should never have multiple traps on any path. It's a code violation. See diy.stackexchange.com/a/83544/35141.
    – isherwood
    Commented Feb 17, 2021 at 21:50
  • Back when clay pipe was common it was normal to have outside traps as you have found out clay leaks and you end up having to snake it. Plastic pipe won’t leak and is now not allowed.
    – Ed Beal
    Commented Feb 17, 2021 at 22:12

1 Answer 1


Soil traps are now banned. I think they were common prior to the 1950s and since your pipe is terracotta that would indicate it predates this time.

  • Both clay and concrete pre 50’s at least on the west coast it was about that time or slightly before orangeberg “asphalt pipe was used”+
    – Ed Beal
    Commented Feb 17, 2021 at 22:15

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