how many CFM at 80PSI? thats the key. You could have 10000 gal, but once that tank is empty, if you dont have the CFM to keep up with the blaster your pressure drops a ton and it doenst effectivly blast. Siphon setups use atleast 15cfm at 80PSI. or 18-20 at 100-110psi with a large nozzle to flow alot of sand. 80psi with med nozzle will blast paint off fine, light rust OK, heavy rust sucks, powercoat is just as bad as heavy rust, and it wont touch undercoating. Even at 110psi it starts to take heavy rust off, will cut through powercoat but its slow (1 inch aobut 1-2 minutes+), and will take 5 minutes to get 1 inch of undercoating off.
A pressure pot is about 4 times as effective as a siphon setup, but the CFM has to be there. The small nozzles for 13-15cfm will let the compressor keep up, but the blast radius is about the size of an pencil so you will be there forever. A med nozzle for 15-20 cfm will do about a 3/8" dia blast circle. 20-30 cfm nozzle will do about 1/2". I ran my pressure pot with the nozzle size my compressor could keep up with and got close to 1/2" dia shot out of it. Those rear trailing arms were mostly painted, some light rust and some heavy undercoating in spots. Took me 30+ mins a pop, and about 150lbs of media (i reclaim mine the best I can). I loose money blasting with my current compressor and pressure pot.
blasting sucks! 