"Max" wrote in message
there's a "T" valve that has a cut off to the filter. When open, the
water flows from the main water line to both the faucet and the
filter, The valve has a cut-off that will shut the flow of water off
going to the filter but allow water to continue to the faucet.

This ensures no water goes to the filters if either there's a leak or
when changing filters.

It's really nothing more than a three way valve under the sink.

Now I understand. Then I'd say the diverter or faucet cartridge is the
culprit.