a standard 2000 sqft roof takes me around 30 gallons of mix, More or less depending on how much moss and how steep it is... so a 60 gallon tank "should" get you a couple roofs but don't forget there is a learning curve! When you start you are probably going to use more
Thanks for the replies.. I have a 35 gallon tank lying around and was hoping it would be okay. I really don't have the room for anything larger. So.. I may have to mix on the job... that means carry an extra15-20 extra gallons of SH.
I used a 65gal tank for a long time, but i'd recommend at least 100gallons.
No don't use your buffer tank you don't want any left over SH running threw your pressure washing pumps, IT would be a pain in the ass to rinse plus the SH will eat up the washers on your bulkheads. ALSO do not put any bulk heads in the bottom of your roof cleaning tank when you do get one.
At least 100 so if you get two decent sized roofs in a day or a larger project, you are less likely to need to go refill your chem tank. I run a 150 Gal tank on our big truck and some days use every drop.