: can you tell me what the purpose of the copper tubing that tee's off from the lines to my sink faucet they are about18 inches long and have caps soldered on the ends. thank you

Richard,
those are air chambers for reduction of water hammer. If or rather when they become waterlogged, they no longer serve that function.
Water hammer arresters will not waterlog. For those of you with the air chambers, shutting off water to the home, and draining down will replenish the air in the chambers.
Terry

• water hammer arresters