Converting Tub to a shower pan

[JSMSKS]

My 89 year old Dad will be visiting us for a few weeks so I decided to replace a tub with a Kohler cast iron shower pan to make life easier for him. The Kohler has a right hand drain. The old and new drain parallel vertically and abut a floor joist. With the old set up someone cut out a 2 x 3 " section of the joist so to feed the p trap on the other side of the drain using 1.5". What are my options and what is best practice to make the new connection?

Thanks for any help you can provide.

 

[Stuff]

Some might say the first thing to address is the notched board.
Can you put the trap where the shower drain is then extend the trap arm through the round hole already in the joist? Then straight in to what is already there. Need to keep it horizontal (1/4" slope) until you get to the vent. Limit is normally 60" for a 2" drain.
Most places want 2" drain for shower. Looks like that is what is there but pictures can confuse me.

 

[Sponsor]

 

[Terry]

I would cut out the old p-trap out, go through the joist and then swing back and pick up the shower drain.
You don't have to hit it straight on. Have the pipe go through offcenter and then swing the trap back to center.

 

[JSMSKS]

Thanks for the replies. Bought the house new and was surprised to floor joist butchery and that it passed inspection! The old drain was 1.5" so I will use a 2" to 1.5" inch reducer sleeve on the 2 inch shower pan drain. This might not be ideal but the total length of 1.5" pipe is less than 2 ft from the connection to the 2" toilet line.

Not sure until I dive into the crawl space again the best route for the p trap. If possible I'd like to avoid cutting the joist even further even though I will be adding a sister joist to it. Would making a big U trap out of 1.5" schedule 40 around the floor joist be a no no?

The cut up joist might explain why the plan is out of level by 3/16.

 

[Terry]

A big U is not the way.
Go through the joist, and put the trap under the shower drain.