The first red wheel is to the left as you enter the sewer, but it only lowers the water level. There are two more wheels as the water goes down : one to the right and one to the far right. If you catch the closer one, you can raise the water where it needs to be to reach the control room door. If not, the one at the far right will raise you to the other wheel level. Do not touch the wheel that is nearest the control door, or you will reset the sewer level.
The one by the door at the upper left is one that you do NOT want to turn: it resets the sewer to when you arrived!
Swim left to the red wheel and turn it, and the water goes down. Swim right, and you may get to the middle wheel as it appears, so you turn that one. If not, turning the one at the far right will lift you up to it. When you have turned the center wheel, you can swim under the wall at left to reach the control room door. Do not click the wheel next to that door. Click on the door.
Beneath the restroom at City park, cross the sewer to reach the first red wheel, which lowers the water. Then find the other two that raise it. When you can reach the control room door at upper left, do not click the red wheel there : just open the door.
Go left and lower the water level with the red wheel. Then raise it again until you can reach the door at the upper left (do NOT turn the wheel there!). Go through the door to find Ratman.
There are three red wheels that lower and raise the water in the sewer. But the one you use in the Control Room is at the upper right, and you have to jump past three rats to reach it.
Ratman is hiding in the Sewer Control Room below City park. Enter the sewer through either of the restrooms. Go left and turn the red control wheel to lower the water. Another red wheel will appear on your right to raise the water again. Swim to the control room door. (see related question)
There are no green wheels. (see related question)
Yougo down into the sewer where Ratman is hiding with his pet rats and stinging flies. Go left and find the red water-control wheel. This will lower the water until you can see another red wheel, to the right, which will raise the level again. Now you can swim over to the left side where the Sewer Door is. Entering the sewer, go on the right side and jump over the biting rats to find the red wheel that drains sludge onto Ratman.
There are 4 in the sewer and one in the control room. Entering the sewer, you go left to find the one that lowers the water. Then you use one or both of the ones that appear on the right, to raise the water level. You do NOT use the one next to the door. Just go inside. The final red wheel is at the upper right, so you have to avoid the three rats there. Turning the wheel dumps sludge on the flies around Ratman, and you can dodge them to reach and capture him.
Turn the red wheel on top of the last ledge.
The door is at the upper left in the main sewer chamber, and you cannot reach it. Use the red control wheel at the left side to lower the water level. Then use the other two red wheels (far right, middle right) to raise it again, to where you can swim under the barrier and reach the stairs.
The first red control wheel is to the left as you enter the water in the sewer room. this wheel lowers the water level. There are 2 more wheels back to the right as the water lowers. The far right one raises the water slightly, to the level of the wheel not as far right. When the water level is just below the Control Room door at upper left, duck under the wall to reach the door.*Do NOT turn the wheel nearest the door, or you will start the cycle all over again.
There are 4 red control wheels in the sewer and one in the control room. Entering the sewer, you go left to find the one that lowers the water. Then you use one or both of the ones that appear on the right, to raise the water level. You do NOT use the one next to the door. Just go inside. The final red wheel is at the upper right, so you have to avoid the three rats there. Turning the wheel dumps sludge on the flies around Ratman, and you can dodge them to reach and capture him.
Ratman is in the sewer control room, under City Park. Enter the restroom at City Park, and go down the drain. When you reach the sewer, swim left to the red control wheel. Turning it lowers the water level. There will be other wheels to the right that raise it again, so that you can swim under the wall to the upper left and reach the Sewer Room door. (see the related question)