Six-Pack of replacement filters for your Doodip tub. How often do you need to change the filter? A lot depends upon usage — are you a daily dipper or just a couple times a week? Does more than one person use the tub? Some people change filters bi-monthly while others wait 60 days. We don’t want to make you pay for filters more often than you need so there is no set replacement recommendation. When it’s dirty, replace it. If you notice the water isn’t circulating well, that’s a good indication that your filter is dirty and ready to be changed.