This is my first post.

When I purchase my house a full bath was roughed into the basement.

I am in the process of installing a shower base in my basement.

The builder roughed in the shower as follows
- 6 inch PVC pipe straight into the concete
- inside the center of the 6 inch pipe is a 2 1/2 inch PVC drain pipe for the shower
- the 2 1/4 drain pipe is connected to a 4 inch 90 about 3 feet down into the concrete.

Based on what I see there is no trap for the shower. I assume the purpose of the 6 inch pipe that surrounds the 2 1/2 drain is to give enough room to install a trap.

Because the 2 1/2 drain pipe runs vertical I am assuming I need to install a S-trap. Put I don't think I have enough room.

Can anyone give me some advice on the proper way to install the trap. Are there any other types of traps I should be using? Thanks