Toilet bowl keeps filling
I have a 5 year old Gerber toilet in my basement. I went downstairs today and I saw that the bathroom was soaked in water and water seeped under the molding into my den area. After trying to figure out where the water was coming from, I found out the toilet is running at times without being flushed. It goes over the water piece that fills up the toilet and keeps running, hence, the overflow. It does not have a ball adjustment, seems it's controlled from a pump.
If I adjust the pump to make it stop filling, a few minutes later the water starts going down and then reaches a point and starts filling up again. Obviously, I have shut off the water valve otherwise I'd be having another flood.
Can this be fixed my me or do I need to call a plumber?