I don't know if your FR691V came with a foam pre-filter or not. If not, I would suggest getting one. The manual says to replace the paper filter every 200 hours. I would do it at every 100 hours.
I don't know if your FR691V came with a foam pre-filter or not. If not, I would suggest getting one. The manual says to replace the paper filter every 200 hours. I would do it at every 100 hours.