Bring large pot of jars back to a boil. Add lids and rims, and remove after one minute. Tip water out of the jars, and set out to fill.
Set jars into same pot used to sterilize. You’ll probably need to remove about 4 quarts of water – leave enough so jars are covered by an inch or two of water. Bring to a boil, cover with the lid, and process in vigorously boiling water for 45 minutes.
While jars are processing, pour tomato water into jars, seal, and set in the fridge. Within a day, you’ll want to strain the tomato water.