Water filters for the Bidet Toilet Seat are not required, but the Bidet Manufactures recommend using either a Sediment or Ion Water Filter for your Bidet Toilet Seat to help keep your Bidet in good working order.
The Sediment Water Filter was designed to keep small particles (particulates) out of the water supply to keep your Bidet Toilet Seat free from clogging and buildup. If you have hard water, then I would suggest the Ion water filter.
Suggested Replacement for water filters are from 6 to 9 months depending on water condition. If you have exceptional water quality or a whole house water filter, then a water filter for your Bidet Toilet Seat won't be necessary.
When you choose 3 Sediment Water Filters the cost is $43.95, giving you a savings of $15.90 over buying just one and no extra shipping charge.
This image is an example of how the Water Filter can be connected to your Bidet Toilet Seat and they can also be connected at the T-connector.