In a large enamel or stainless steel bowl, mix the cucumbers, onion, peppers, celery, salt, turmeric, and water. Let stand for 12 hours or overnight, then drain in a strainer, lightly pressing out any excess liquid. Set aside.
Tie up cinnamon, cloves, and allspice in a piece of cheesecloth. In a large, heavy, enamel or stainless steel saucepan, bring the spices and vinegar to a boil over moderate heat. Reduce the heat to low and. simmer, uncovered, for 15 minutes.
Add the tomatoes, increase the heat to moderate, and bring the mixture. to a boil. Reduce the heat to low and simmer, partially covered, until the tomatoes resemble a puree - about 30 minutes. Add the sugar and mustard. seeds, cover, and let stand overnight at room temperature.
Add the drained vegetables to the tomato mixture and bring to a boil over moderately high heat. Then reduce the heat to low and simmer, uncovered, until most of the liquid has evaporated - 25 to 30 minutes. Remove the spice bag.
Ladle into 4 hot, sterilized, 1/2 pint preserving jars, leaving 1/2 inch of head space. Wipe the jar rims clean, seal, and process in a boiling water bath for 10 minutes. Label, then let the relish mellow in a cool dry place for. at least 3 weeks before using. Will keep for up to 1 year. Refrigerate after opening.