Frustrated with adding concentrate to a gallon when you have a exact number of gallons of volume in a sprayer . I would suggest adding 1.5 gallons of water first then adding 1.5 Quarts to it . ( 48 fluid ounces ) This leaves only 16 oz of spare volume .. Then mark on the side the fill level so next time it does not require exact measurement of the concentrate . Alternately if you have a smidgen left of working solution in the sprayer add the 48 0z by measurement then fill to the 2 gallon mark .