I put the cucumbers, onions and peppers in chunks into my food processor and whirred them around until they were in small pieces, but you can also hand chop your vegetables.
Place vegetables in a large bowl. Sprinkle with salt and mix around. Cover with cold water and let stand 2 hours, or overnight.
Drain and press out excess liquid in a colander.
Combine sugar, vinegar, celery seed and mustard seed in a non-reactive large pot. Bring to a boil, stirring to dissolve sugar.
Add drained vegetables and bring to boil again. Lower heat and simmer 10 minutes.
Pack into hot sterilized pint jars, leaving 1/4 inch head space. Place caps on and tighten. Place in hot water bath and process for 10 minutes.
Makes 4 pint jars.