Can I use the gallon concentrate to re fill the 32z hose end sprayer ?I don't want to get on roof to hit high spots and can do 75% with pump sprayer.

If both spray end and concentrate dilute at 5:1 how can using gallon concentrate as refill over dilute?

The hose end sprayer is calibrated specifically for the Roof Cleaner formula to siphon out at a 5 to 1 mix ratio. If you were to purchase the concentrate, you would manually mix at a 5 to 1 ratio (1-part product to 5-parts water or 21 oz. of product to every gallon of water) and apply with a hand pump garden sprayer. It cannot be used as a refill for the hose end sprayer bottle. The formulation would overdilute and you would not get the desired results.