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.
You enter the sewer through the restrooms in the park (boys use the boys' room, girls use the girls' room).
Both restrooms (boy and girl) lead to the sewer where Ratman is hiding.
There is a sewer in Early Poptropica, below Main Street, with lots of spiders. The sewer in Super Power Island is under the restrooms in City Park. Go down from inside either one (gender specific).
Ratman is hiding in the sewer under City Park, with his pet rats and stinging flies.
The toilets in Poptropica are decorative, except that the restrooms on Super Power Island lead directly to the sewer where Ratman is hiding.
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)
You should be transported to the Prison when you beat him, and receive a sticker on your Superhero ID card. If this doesn't happen, you can leave the way you came in : left to the control door, right through the flooded sewer, and up through the restroom floor.
The girls' restroom is to the right side at City Park on Super Power island. You can only enter the restroom that matches the gender of your avatar, boy or girl. Either restroom leads to the sewer where Ratman is hiding.
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.
No. Your Poptropican will never poop. However, on Super Power Island, you have to enter the park restroom to reach the sewer where Ratman is hiding.
Ratman is on Super Power Island. There is a large rat in the sewer entrance to the factory on 24 Carrot Island (climb up into the bypass pipe to elude him).
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.