In the process of bathroom remodel.
Previously, I had a built in fiberglass shower surround. I mention this because I have had to drop the plumbing to go below to prepare for tile flooring.

My question - hope this accurately describes my problem - and it's a mobile home.

From shower vent (T pipe and previously installed pipes); 1 and 1/2 PVC pipe 2 ft long (this is glued) with a 45 degree elbow on back end. (Elbow not yet glued). The elbow has another foot of pvc pipe from the other end, which connects to the actual P-Trap shower drain (not yet glued).

Husband believes that the P-Trap Elbow connecting to PVC needs to be higher than 45 degree elbow that connects to vent pipe to drain properly - Otherwise, how will it drain properly? (This creates a massive problem because I would then be above floor level with PVC piping)

From what I researched so far, elbow of P-Trap and elbow of 45 degree elbow coming from vent need to be at same level?

Without tearing the whole house down, I am not sure if I have additional venting, but with a 2,400 sq foot mobile, I would hope so.

Should I still follow the standard slope in drainage line? - does it matter as far as drainage for shower and sewer?

I definitely want to get it right the first time and not have problems in the future.

I would love to add picture, but for some reason, my pic will not come through via email.

I'm trying to follow how adding a tile floor has anything to do with the tub drain. I may have just miss read you post so bear with me.
A tub will be sitting on the subflooring not the tile.

A few issues you may run into.
Mobil homes sometimes take odd ball sized tubs. Also a modern tub will also take a 2" drain not 1-1/2".
If you intend to use real tile on that floor you better take a closer look at what you have for a subfloor, some but not all mobile homes used partical board or thinner subflooring, narrow floor joist that are spaced to far apart then what will be needed to fully support tile without some added steps taken.

On the plumbing end - the important things are that the vent ties into the system downstream of the trap and that the vent line continues to run uphill away from where it ties in to the drain. This will allow the system to vent without sucking the standing water in the trap out (which is why there is a vent system in the first place). the relative heights of the trap and the "T" where the vent ties in really doesn't matter as long as the vent line always travels uphill and has no traps that could hold water.

Thanks for the replies.
Joecaption, it is the shower area I'm referencing.
The sub-floor was damaged,(which prompted the whole DIY). It has been removed and I plan on replacing with plywood and cement backer board of course. Your comments regarding the joists brings me to a new question not plumbing related.
The joists are actual 2x4, spaced 1 and 1/2 foot apart. Is this sufficient to support tile?
Thanks for the heads up regarding the bathtub drain.

Jaybee;
Just so I am understanding right. When you say "as long as the vent line always travels uphill" are you referencing the plumbing line that travels to the vent pipe?

Thanks

Yes, I am referring to the vent line. The important thing about the vent is that it always provides a clear air path to wherever it exits the house.

2x4 joists are not going to be enough. 2x4's are never acceptable for use as joists in any application (except obviously a trailer). But unless they are only spanning about 2' the 2x4's will flex too much for tile. You really need to sister them with 2x8 to keep a stiff floor.