The gang has been pumping the swimming pool to protect the house from catching fire, yet the water level is the same as before they started pumping.
Kelly has a flashback to the previous fire she was in, but the first things she envisions are people running down to the main floor from upstairs and out the front door. These are all things that were shown onscreen during that fire, but she wouldn't have seen those things, since she was in the basement the entire time and didn't know there was a fire until it was out of control.
If they were truly trying to save the house they would have removed the nozzle from the end to allow more water to come out of the hose at one time.