Okay so I'm working on my first DIY bathroom remodel and decided to relocate my toilet across the room to a more convenient location that would allow us to extend our vanity.

Everything has gone pretty well or so I thought until after I hooked up the new vent line to the existing system which goes straight up into the attic and vents to the roof.

First, when I cut into the vent line to relocate it in the bathroom I noticed it had water in it, which I figured normal since it vents to the roof and probably some water enters when it rains. I would expect this small amount of water to eventually flow through the system into the sewer.

What I did not expect after hooking up my new toilet drain branch into the main line was for water to back up in the 90 degree sweeping elbow that my toilet flange will eventually be connected to. There is about 1" of water in the 3" pipe. The new branch plumbed into the main 3" drain passing through my bathroom is about 2 1/2' and I did not do anything special to pitch the branch. I figured since the toilet water is dropping down the 90 degree sweeping elbow and passing a short distance I would not need to pitch the run, nor am I really sure how I would pitch it.

So my questions are:
1. Is it normal for a little standing water to accumulate in the toilet drain line?

2. Should this small run be pitched? How could I pitch it?

Appreciate any comments to the linked picture of the new work in case anything looks incorrect.

Thank you for your time.

[docs.google.com]

i don't say this very often but you are in this way over your head.
it needs to be ripped out and you need to get advice here or from a plumber at home as to how to pipe this.
you have drains backpitched, the tub is not vented and lord knows what else you have done wrong.
you should have asked FIRST...

1. No it is not normal.
2. Can you shorten the pipe from the 90 up to the flange, and in turn lift the 90 ?
You need 1/4"of rise per foot on the drain pipe.

quote; 1. Is it normal for a little standing water to accumulate in the toilet drain line?

No.

2. Should this small run be pitched? How could I pitch it?

Yes, You have to raise it somehow, possibly by revising the piping system.

3. Your shower is NOT vented.

4. That vent through the roof is strictly cosmetic, to look good, because it does not provide any useful function where it is connected to the drain system.

5. I would be concerned about HOW you intend to connect that dual sink configuration.