Hi,
I am in the process of enlarging my downstairs bathroom in a tri-level home.
I am moving the drain to center it in the shower. I have removed the old concrete and moved the drain about 18 inches. We would like to drop the shower floor a couple of inches as I am very tall and the bathroom has a fairly low ceiling. My question is about whether there is a minimum height from the p-trap to the top of the drain. The way I have it, the drain is only 2 1/2 inches above the top of the p-trap. There is 6 3/4 drop from the drain to the main sewer line. Total distance from the drain to main is 32" The upstairs junction is about four feet away, the floor drain in the laundry room is about 20" away and the toilet which is down the main line going out is about six feet away. Thanks, Amado

If I read your question correctly, the drain is going to have to go down between the trap and main sewer line with the vent. If so, as I have learned from Tom here, that makes it a long forbidden ''S'' trap. It would add a couple of elbows too, which I already knew was asking for trouble.

Since you have already cut the concrete, just dig down a little deeper and run the extended drain at the same level as the old. Big problem will be keeping the gravel from falling out from under the slab.

If I have misread your question, post back and assure Tom the extended drain won't go down after the trap until where the old one was vented. Either way, you will be good to go once Tom answers.

I guess my question wasn't clear enough. The trap is simply farther away from the main sewer line. It did not have a vent between the trap and the main line. The P-trap is directly below the drain and of normal configuration.
I just wanted to know if there is a minimum height requirement from the top of the trap where it heads down to the main line and the top of the drain. There won't be a problem with the gravel escaping, which in this case is sand because there is a perimeter foundation wall surrounding the shower area.
The guy at Lowe's said that as long as the drain is above the level of the pipe heading out of the trap that it will work just fine. Thanks

"I just wanted to know if there is a minimum height requirement from the top of the trap where it heads down to the main line and the top of the drain."

There is no minimum or maximum requirement between the top of the trap and the drain as long as the trap is under the cement and the raiser comes out of the cement high enough to connect the shower drain. Good luck, Tom