[bewaretheirs]

At one point Brita distributed a spring-driven mechanical ratchet counter that would sit on top of the filter cartridge; it had some sort of diaphragm arrangement that would sense the water level and "tick" once per refill cycle and tell you when it was time to swap in a new filter.

[ska]

I wonder why they go rid of it. Was this shipped with every filter or was it a think you reset and put on again? Do you recall if it could tell the difference between a partial fill and full fill?

What you really want is to measure the volume through the filter, but I can't think of a way to do that cheaply and mechanical only.

[bewaretheirs]

It was reusable. You would turn it back to the start to reset it when you'd pull it off the top of the old filter and stick it on top of the new one.

I don't recall whether it came with the pitcher or as a bonus item included in a filter-multipack. It just counted one "tick" on a ratchet per fill/empty cycle, no attempt to measure volume or fractional fills.

[lozenge]

They probably consider the electronic version more "modern". Even though it contains a non replaceable, non rechargeable battery.