Plumbing – Should I install a drain trap on the main pipe before it exits the home

p-trappipeplumbing

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

Best Answer

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.