Wash jars and lids in hot soapy water; rinse with warm water.
Fill canning pot half full of water; add jars and water to cover. Bring water to a boil, reduce heat and simmer.
Place lids in water to cover in a small saucepan; bring water to a simmer. Simmer until ready to use.
Remove and drain jars and lids, one at a time, as needed for filling.
To prepare the peaches:
In a bowl, combine 4 quarts water and lemon juice. Fill another bowl with ice water.
Fill a stock pot ¾ full of water; bring to a boil. Working in batches, add peaches and boil for 20 seconds or until skins easily peel away; remove with slotted spoon and transfer to ice water.
Use a paring knife to slip skin off peaches; cut in half and remove pits. Place in bowl with lemon water to prevent browning.
In a saucepan, combine 1 quart (4 cups) water and Splenda Sweetener; bring to a boil over medium-high heat. Turn off heat; cover saucepan to keep syrup hot.
To can the peaches:
Drain peaches; place into prepared jars. Ladle hot syrup into jars, leaving ½” of headspace at top of jars. Wipe jar rims and threads. Cover with 2-piece lids; tighten bands.
Place jars on rack in canning pot. (Water must cover jars by at least 1”; add boiling water, if necessary.) Cover; bring water to a gentle boil.
Process for 25 minutes. Remove jars and place upright on a towel to cool completely.
After jars cool, check seals by pressing center of lid with finger. (If lid springs back, lid is not sealed and refrigeration is necessary.)
Store in a cool, dark place for up to 1 year. Once opened, store refrigerated and use within 2 weeks.