A call for a toilet that was not flushing or filling up, turned out to be solid algae blockage in the piping of the pump to the rainwater tank. This was preventing the rain water pump and piping from allowing water to pass. If you are drinking the filtered rainwater, cleaning your rain water tank is the only option when this happens. Algae will continue regrow and infest the area again and again. If your rainwater tank is only for toilet use, throw a chlorine tablet in the tank periodically to kill any algae from growing.