Second diagram? Where? All i found were pictures with arrows which was obvious in few seconds.
Then i found hint to blue room - five in a row - which turned green light in blue room on, but nothing else.

There are diagrams on the wall. The first shows a (4) leaf clover, (2) people, a (3) pronged trident, then (1) tree. The code is 4231

The second diagram shows shapes divided into segments. The first is a circle split into (3), then a square with (1) area, followed by a diamond split into (2), then a square split into (4). The code is 3124.

The secret diagram shows shapes and tally marks. The tally marks represent how many fumium pipes are behind each valve. The LEDs above the valves are irrelevant for this code. The shapes are Square - (4) lines. A 45degree angle - (2) lines. A single line - (1) line. Then a triangle - (3) lines. If these are entered into the appropriate valves based on the number of fumium pipes behind each one - the code is 1342

I would love to actually understand this puzzle. Can anyone explain each of them?

It should have been a simple puzzle with visual cues of the liquid flowing. terrible puzzle.

Do you know what the pressure plates on the floor are for?

Indeed. A bunch of us (myself included) just did that TBH.
But if you're going to give up on a puzzle and brute force it, might as well just get the codes directly.

Not that hard even to brute force. Only like 256 combinations

I found all the emoji,
I didn't understand the theory of regular route puzzles.
However, after thinking about it, I finally understood it.
Thank you for your reply.

@Meat Man
There's three different scrbbles on walls to find that hint to the various codes.

I found the other code from the hint,
Valve with one light => 3 lit leds
Valve with two lights => 1 lit led
Valve with three lights => 2 lit leds
Valve with four lights => 4 lit leds
Only this, I did not understand the theory until the end.
Is there a hint somewhere?