I would like to add a bathroom to my house. The house sits on a slab, and there is a vented drain of 2 1/2" cast iron, which runs to the main drain at front of the house. It currently is for the laundry room. Can I tap into this pipe for a toilet, shower, and sink for the new bathroom. It's placement will allow for min. of 1/4" slope for all added fixtures, without cutting into the slab.

The sink and shower would work OK, but the line is too thin for waste from toilet. It also may not meet code.

I am not a plumber and not up on codes, but from reading other posts most areas require 4 inch for toilet waste.

One of the experts will be by to add to this answer.

Chuck

Hi Coreyk..

You have a 2.5" OD (outside diameter) fitting there right? If so, that is 2" cast iron pipe and isn't even close to acceptable for a bathroom.

At a minimum you will need a 3" drain (3.5" OD) to install that bathroom above the slab. Local codes may require up to 4" (4.75"OD) drain under a slab... ;)

Check your local plumbing code requirements by calling a local inspector if needed. You may also want to ask the inspector if WET VENTING is allowed... if so it is a usually a real time/material saver... and that is never a bad thing!

Back to you...

Mark

HI CHUCK...dead on advice!

Knew I would get u in on it Mark. Will try to be more careful in future.

Thanks

Chuck

Hi Chuck...

Your answer was dead on... you post anytime. Always sound advice from you!

Thanks...

These darn new glasses only let me see every other word. I read dead advice.Have to get them fixed. LOL

Chuck

I understand now! Thanks Chuck :)

Can I tap into this pipe for a toilet, shower, and sink for the new bathroom. It's placement will allow for min. of 1/4" slope for all added fixtures, without cutting into the slab.
Nope! Chuck and Mark gave you good advice.
The slab will have to come up and the 4" house main exposed., You may then cut in a 4" wye or combination to pick up the toilet.
Here's a typical installation using one vent for the entire group. (see image). Good luck, Tom