The bathroom scene is key!
Season 5 spoilers!
The flooded bathroom scene isn’t just comedic relief, it’s the key to curing any Byler doubt that may have come from the field scene and Robin’s speech being used when Will unlocks his powers!
It’s already been pointed out that Mike and Will trying to stop the water coming out of the pipes is symbolism for them trying to contain their feelings for each other (water is a common symbol for emotions in art), but IT ALSO CONNECTS TO OTHER IMPORTANT SCENES IN THIS EPISODE AND IN THE SHOW OVERALL.
Note that Mike is the one who hits the pipe, leaving a dent in it.
Mike is the one who has been putting out signals this whole time (visible signs of his interest, like the visible dent in the pipe). The vast majority of Byler evidence out there relates to Mike’s words and actions. He’s the one who’s possessive and protective of Will since Season 1. He’s the one who goes out of his way to apologize whenever they have a fight in order to maintain their relationship. He’s the one who flirted and obviously check out Will during the “Cool.” “Cool.” scene.
That metaphorical dent in the pipe has been there for a long time, BUT NOW WILL CAN SEE IT, thanks to Robin. When Mike first hit the pipe, the water was still contained. It only started to leak when the boy turned it while coming down the ladder, and the dent became visible to us.
When he turned the pipe, the water started spilling out. I would argue that Robin pointing out signals to Will is what turned the metaphorical pipe and allowed Will to see the signals Mike had been sending this whole time.
Note how they show him swallowing when Robin describes what signals to look for.
And then we seen him looking like he’s thinking back for signals he might have missed. He's also breathing heavier here, like he's realized something important.
Now that Will can see the signals, he decides to try flirting with Mike in the field. Mike responds to the playful shove Will gave him by smiling and looking down bashfully but then getting a slightly uncomfortable look and walking away.
I’ve seen people getting doubt because of this reaction, but it’s totally normal for Mike! He’s used to being the one putting signals out there, and he always gets nervous whenever Will initiates something and he thinks he might get found out. The infamous triple take is the main example of this. He looks over at Will only to find that Will is already looking at him (like that!), gets really flustered, and goes back to digging, ignoring Will.
So, Will finally sees the signals (dent in the pipe), and his flirting is the water coming out of the pipe. He’s finally starting to let some of his feeling (water) show instead of being contained inside himself (the pipe). Note that Mike is the first one to notice that the pipes are leaking when drops of water start falling onto his face.
He sticks his head up into the bathroom and sees that not one, but TWO pipes are leaking!
The first pipe he sees is only leaking a little bit, but the second one he notices is really going. To me, this signals that Will letting a little bit of his feelings show (letting a little water come out of the first pipe, which is the one that hit Mike in the face) is breaking something open in Mike (the second heavily-leaking pipe).
And look how scared Mike is when he sees this! Mike has raging internalized homophobia, and he’s afraid that the leaking water (cough, snowball) is going to turn into a flood (cough, avalanche) that won't be able to be contained and that other people (the guards in the barracks or, metaphorically, the people living in conservative Hawkins) will see, which will cause them to come after him and Will.
Mike and Will try to stop the water coming out together, but they’re getting completely soaked. They can’t stop it from spilling out all over them. It can’t be contained anymore.
Note how Mike asks Will to take off his jacket to patch up the leak.
Mike is also wearing a jacket, so why doesn’t he just use his? I think it’s because Will’s the one who flirted in the field. He really showed his hand for the first time, which is what broke that feeling open in Mike. Now Mike is scared and wants Will to do something to help him put the feelings back inside so that Mike doesn’t have to deal with this sudden flood of emotions he’s experiencing. (See this post for more thoughts on the jackets.)
There are other symbolic things in this scene, like the male orgasm imagery (they’ve got their hands wrapped around a pipe that’s spurting liquid everywhere in a location they refer to as “Dick”…..) and the shot of them trying to keep the guards at bay by blocking the (closet?) door with Derek in between them wearing a rainbowish shirt.
But then the guards get in (which I’m reading as their feelings eventually being discovered by others), and they get hauled out into the main open space in the base. It’s here that the demogorgons start attacking. Venca eventually comes out and taunts Will for being weak, using images of him being distraught because he thinks Mike doesn’t love him back.
But when the Demogorgon is about to attack Mike, Will gets his inner movie of the start of their friendship on the swings, which is THE MEMORY THAT MIKE USED TO REACH WILL WHILE HE WAS POSSESSED IN SEASON 2. I’ve seen a lot of people getting Byler doubt because of Robin’s speech being used during that sequence, and others have rightfully pointed out that Mike isn’t Will’s Tammy because the love at first sight stuff parallels what he told El in the Season 4 “love confession.” There’s also the parallel of him being Vickie, who was in a straight-appearing relationship before getting with Robin.
But I think the most important thing here is that water represents emotions in art, and WILL IS SOAKED IN THE WATER FROM THE LEAKING BATHROOM PIPES (specifically, the pipe that was really bursting, which I think was Mike's feelings for Will) while he’s having this moment of accepting himself and his love for Mike.
Will wasn’t letting go of Mike here. Will saw the signals. He suspects that Mike likes him back, or he wouldn't have flirted. He remembers how special their relationship is and has always been. It's not a coincidence that the first thing we see in his movie was the scene Mike described in Season 2. It was what gave him the strength to break through the possession then, and it's what helped him discover his power now.
AND MIKE IS ALSO STANDING THERE COVERED IN WATER FROM THE EXACT SAME SOURCE! The water connects them. Nobody else in this scene is wet from the flood. It's just them. They're both becoming aware of each other's feelings now, and I think the look of awe and admiration on Mike’s face when he sees Will save him with his new-found powers indicates that he’s going to start to accept his feelings soon too.
Edit: Moved the Keep Reading down to show the main point now that most people have seen Vol 1 & updated tags
