Why has my 10 year old had poo like water for 7 day and he is ok in every other way please help?

Diarrhea diet: Most pediatricians will recommend the BRAT diet for children with diarrhea ( Bananas, Rice, Applesauce, Toast). Most vegetables are fine to feed during this time, but excessive fruits (especially those low in fiber or acidic) may contribute to or make diarrhea worse. Diarrhea lasting more than a few days or diarrhea with blood warrants evaluation by a doctor.