I took out a one piece shower and tub surround from the 80s and in it's place I'm going to install a surround standing shower, no tub. The drain for the shower is in the middle of the floor so I need to get it to where the old tub drain was. The trap needs to go under the drain, I assume, and then I need to get the pipe to where the old tub drain was. I'm going to cut the old P-trap off the pipe and run the pipe to where the p trap is. My question is, does the pipe from the shower drain need to be at a pitch towards the old location or can it be straight. I don't think it will be pitched once it's installed and I'm not sure if that's a requirement

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All drains need to be pitched, 1/4" per ft is usually sufficient.

 

So I was thinking about this. If all the connections are straight when you glue them, how do you pitch it? Would I need and adapter that makes it run at a pitch?
Second question, since I started working on the drain. How far down from the drain does the P trap need to be? The shower floor sits 3 inches off the flooring, can I start the P trap after the 3 inches or do I need to drop it lower into the floor?

 

When you solvent weld a connection there is enough tolerance in the fitting to hold the pipe at the correct pitch of 1/4" per foot and you hold it that way for about 15 seconds until the solvent has set up enough to hold it there.

The p trap is immediately below the drain. So if you have a shower with a center drain, you put your p trap in the center and raise it up so all the pipe from there to your existing is pitched at 1/4" per foot.

With most showers you don't glue the vertical part into the p trap until you know the final drain height. You glue it in last when you are setting the drain. And if you have a pre-made shower pan you usually want to get the type of drain that you set from above after the shower pan has been installed. And you pretty much need to have the pan there to determine exactly where the p trap should go.

 

Thanks! I think I have what ai need to be successful. We'll see