Question:
Water worked fine up until about two weeks ago.

Kitchen faucet is two handle Moen. House is 30 years old but kitchen remodeled about a year ago. Copper water pipes throughout house.

Have GE dual filter water filtration system tapped into the cold water line with separate faucet for the filtered water mounted to sink.

Filters changed about 3 months ago (6 month lifecycle)

Meanwhile, the hot water side works fine.

Cutting off the water line to the filter (it has a cutoff where it's tapped into the cold water line), has no effect. The cold water will still shut off with a clunk after 10-15 seconds.

No other water lines in the house has this problem.

Any ideas what may be causing this?

Answer: That would be my first guess, but he said the hot water works fine. Could be the filter cartridge though, is somewhat clogged giving a pressure drop and causing the spray diverter to block the line.

My first step would be to change the filter, then check the diverter, then the washer/cartridge for the cold water tap.

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.