Metal drain system replacement w/ PVC

[brassmookie]

Recently bought an old house with old drain pipes. I'm in the process of figuring out how to replace the metal pipes with PVC. A couple of questions. For one, the original system includes a p-trap on on the mainline. I had a plumber come in at some point that mentioned that was probably no longer required by code (I'm in NY). Whether or not it is required by code, it is still best practice to have a trap off the mainline, or is that unnecessarily redundant since every outlet off of the mainline will have its own trap? Secondly, there are a couple of large elbows that have a left and right inlet into the elbow. I haven't been able to find the PVC equivalent of that particular piece. Would I be able to use something like this, and simply cap off the extra hub?

 

[CT18]

Originally I believe house traps were for critters, at least that is what the old timers told me. You may want to contact the city to see if they are still required. If not I would remove. They can cause blockage issues at some point. If it were me I would replace the galvanized pipe and the house trap. I am a cast iron fan, the old they don't make it like they used to idea. I still have leaded cast iron in my house. I replaced the 2" galv. run to the tub with PVC

 

[Twowaxhack]

High levels of sewer gas can crack cast iron. House traps prevented that. Probably helped with all the s-traps that didn’t work 100% of the time. I seen sewer gas eat copper DWV. Paper thin and green.

Some house can get tremendous sewer gas flow depending what’s up stream or downstream. Your house could vent the whole street !

 

[brassmookie]

thanks for the input guys. so far that's one vote for the house trap and one vote against...

 

[Twowaxhack]

No, I wouldn’t use a house trap.