Blazer Spray Tank Cleaner is mixed at 0.32 oz to a gallon of water. For your 4 gallon tank, you will mix 1.28 oz.
Blazer Sprayer Tank Cleaner is a spray tank cleaner that neutralizes and cleans excess residue from pesticides and fertilizers, which includes residue from herbicides and insecticides.
Per the product label for Blazer Spray Tank Cleaner: : For 100-300 gallon tanks use 16 ounces of Blazer with 50 gallons of water. Close boom valve, add 50 gallons of water to tank, turn on agitation and add 16 ounces of Blazer Spray Tank Cleaner. This breaks down to about 0.32 fl oz per gallon of water
Blazer Spray Tank Cleaner would be more ideal for cleaning 100 to 300 gallon tank sprayers using 16fl oz with 50 gallons of water.
For cleaning smaller tank sprayers, Prime Source's Tank Cleaner Select would be used at 1 fl oz per gallon of water and for large tanks, add 32 fl oz for every 400 gallons of water. View the full product label for more information.