i'm at a loss

I hate you so much right now. Also I think it's 5
- It's only 5. It just overflows.
  
  Depends on the flow from the faucet.
  If it is filling 1 faster then water can move between then order will be 1->2->5
  If it is slow enough then just 5 fills.
  Everything else will be dry. Between 2 to 3 is sealed too. Without lids there is a lot of issues.
- Yeah nothing will fill up until 5 is full. And then since 4 has a leak it, I think basically ONLY 5 will fill.
- It was your comment that made me realise
  
  It was your comment that made me realize, agtwr a day later. Damn

None. The water is not running.
- All the candidates are thanked for their time and asked to leave except you, who get invited to join MIB.
  
  Morons In Blindfolds
- Looks like they’re all full of air already
- 😡

5
Also, you suck.
- Depends on how fast the liquid is flowing in.
  Or, actually, can they even "fill"? These are 2D objects.
  
  Is this that "loss" comic? Why is everyone mad?
- The actual joke aside, 4 has a hole in it, so it won't.
  
  ??? 4 and 5 are not connected
  
  5 fills from 2, not 4.
  
  And 3 is blocked
  
  Oh yeah, I got so losst

Unless I completely misunderstand how this works, I think 5 is the only one that will fill up. It then overflows, preventing any of the taller ones from filling. 7 is shallower but won't start filling until 3 gets fuller than 5, which it never will. I assume the blockage between 2 and 3 is a mistake.
- You are correct and I agree, but look again.
  At the comments.
  Then at the image.
  Forget all about the water, and the question.
  If necessary, reread the title.
  Groan.
  
  Please help. I have nightmares of being in a room where everyone else is just waiting patiently for me to remember the thing I forgot/figure out what is happening.
  Help
  
  Goddammit.
  
  By far the most annoying meme and it's not even funny.
  
  Yeah I just got it seeing it for the second time in my feed lol
- I think you’re right. Unfortunately, we’ll still have to chalk this up as a loss.
  
  Like losing the game? That was also annoying and the internet stopped doing it eventually.

1 fills up first. the spigot is much winder than the tube so the glass will fill faster than it can drain.
Also rule
- who's to say it isn't a slow faucet?
  
  If its not properly installed I will call a plumber to fix it.
- That's assuming the valve is open all the way and that there's a bunch of water pressure behind the spigot. It should be entirely possible to create a very slow trickle by having a massive body of water behind the spigot (making it functionally infinite) but having only a small part of the entrance beneath the surface.

5
Wait... Fuck!
- this is right. Even if 2 to 3 is open.
  The only other candidate is 1. If the faucet has much higher flow than the pipe from 1 to 2 can drain away, then 1 can fill up faster than it drains.
  
  5 is correct but this is a loss leader.

5, but it also depends on the circumstances. What liquid is used, temperature, viscosity, etc. There's some material science stuff that's far beyond the intended scope of this question.
- Why 5?
  
  1 fills up halfway, which then overflows in 2. The bottom of 2 has a pipe running out of it, which is directed into 5

I actually started to figure out the sequence...then I realized...fuck you, take my up vote
- :3
  
  ?

All of them are already full of air.
- What if this experiment is done in space near a black hole
  
  Is full of Hawking radiation and dreams.

~~:.|:;~~
- DAMNIT... YOU WIN!

OH İTS THE FUCKİNG LOSS COMİC

5 which begins to overflow into the room
7
4 and 6
2 and 3
1
This is assuming this is a cross section of something 3d and not something 2d otherwise air packets would get trapped and prevent some of this.
- 5 and 4 are the only ones getting water other than 1 and 2. 3 has a solid line blocking the flow into it, and even if that wasn't there, since 4 has a hole/drain in the bottom and 5 can overflow, 3 can't fill enough to reach the outflow. 5 is the only one that can fill up.
  
  Wrong! The room will begin filling with water from the overflow!

I'd recognise that pattern anywhere, but I focused in on the problem and almost didn't notice your dasterdly deed
- What pattern? Judging by the comments this is some kind of trick but I don't know what it is lol
  
  https://knowyourmeme.com/memes/loss
  
  As other replies have said and linked to, it's meant to be "loss"
  Though OP slightly changed the template to fit the puzzle, as the right hand corner is meant to have the shorter piece. That threw me off as well.
  
  It's the "loss" meme
  
  It’s a reference to this
  
  The left half is definitely a penis. Not sure what it is poking into on the right though.
- ... fuck.

Depends on how much you turn on the tap. If you fürn it up completely its 1,else its 5.
- Depends on diameter of the pipes leading out too. They look small in the image, but if they're big enough to handle the max flow out of the faucet, 5 will still fill up first.

i hate you.
edit: read replies before telling me that 7 is walled off
but ignoring my loss, if everything is pressurized i think 7 if unpressurized i think 5
- The pipe from 2-3 is walled off though.
  
  well i didn't see that lol
- 7 won't ever fill because the pipe from 2 to 3 is blocked off.
  
  well i didn't see that lol
- Ignoring the walled off stuff, can you ELI5 why pressurized vs not changes things and how so?
  
  Might be an airlock? It's hard for me to predict how fluids will really flow
  
  my logic was that it's the shortest way and therefore has the least resistance and therefore the highest flowrate.
  while unpressurized gravity would take over

They are all full already, of air.
- What if the system is contained within a vacuum chamber?

All I know is, 7 is leaking out.
- Dude, so dark… I love it.

There's only one "one" in the diagram, so I'm gonna say the one marked "1." Pretty easy.
- God dammit I was five minutes late

- The connection between 2 and 3 is blocked.
  
  Damn, I didn't even notice that.
  
  Even if you assume that it is not blocked, it is still 5. The pipe from 2 to 3 is never reached because 4 leaks out the hole in the bottom. Assume that the hole in the bottom is a flaw and 4 still leaks out the top before the pipe to 3 is reached.
- 1 can also fill up if the flow from the faucet is higher than what can exit through the pipe connecting to 2.
  
  There it is!!! That connector is too narrow, only way it isnt 1 is if the pressure is criminally low.

Wouldn't scale and viscosity play a role? Seriously, imagine a river vs a capillary tube. Also how many dimensions? And forces involved? Is that a blockage between 2 and 3? Are the walls breakable? How will the fluid hold air? Are the lines into structure 5 lower than the walls? Is this in a vacuum?
- you may be overthinking it
- There is no mention of any fluid involved, just a faucet. So lets think inside of the box and assume we have some form of 2d-gravity and it is going to rain a newtonian fluid? I think most surface area on the top is draining into 5. If it snows the whole sheet can turn white and the problem is gone, too.
- Also, these structures are all 2 dimensional.
- It does not specify what they are being filled with. They are all already filled with air.

I came in to comment, "it probably would probably be 5, but I think it would depend on the flow rate?"
But reading the other comments, it looks like I'm OOTL on something? 🧐
- im at a loss too
- There might be something further upstream. All the way upstream.
  ::: spoiler spoiler-title point zero, in fact :::

5

The faucet

1
- nothin wrong with me
  
  2

5

I got it! First, the free floating faucet will drop into bucket one. The impact will certainly break its connecting tube and broken 1 + faucet collapse into 4. Therefore 4 will be broken but full of shards.
- If you're lucky, one of the shards will block the hole at the bottom of 4
  
  If you're lucky, there is a bottom below the hole that everything is standing on. Otherwise everything is loss in a void.

It's a sad day. They all stay empty. Such a loss.

5
- Yes but Title

I wish these were drawn as closed containers

We'll done.

The number of people in these comments who already understand the self-siphoning nature of water with zero explanation required makes me so proud to be here among them.

Depends on the flow rate, but most likely 1 if the tap is running fast. Otherwise I have no idea.
Also, what's with these comments? What's so special/clever about this pic?
- Someone would say you're at a...loss
  
  Definitely cause your hint isn't helping.

Ha. Trick question! All of them are already full of air, and niether the flow rate nor the direction (or lack) of gravity was specified anyway. You lose. :)

I think, Number 7 will stay empty for some time.

7

This diagram scratches my brain real good, especially thinking about it getting filled