Generally a bladder type water tank due to costs. If the intension is to just use HPA and not a cross of HPA & Air assist then you would want a higher pressure capacity in most cases for the nozzles.
Amtrol has a very good tank. Here is a video on there manufacturing process.
Note: Set the bladder pressure 2LBS lower then the water pump cut in.
THERM-X-TROL ST-25V Expansion Tank (10.3 Gallon Volume)
THERM-X-TROL ST-25V Expansion Tank
WX-201 (143S29), 14 Gal WELL-X-TROL Well Tank (Stand)
JABSCO 1 LITER ACCUMULATOR TANK W/ INTERNAL BLADDER
Pressure: 125 psi, Volume: 1 liter Tank
Jabsco 1 Liter Accumulator
SHURflo’s Pre-Pressurized Accumulator Tank
Maximum PSI : 125 PSI [8.75 BAR]
SHURflo Water Tank
SHURflo 2 Gallon Stainless Steel Accumulator
Maximum PSI : 100 PSI [7.0 BAR] (Some sites have stated 120psi max.)
Shop for pricing on everything obviously.
Shurflo: Pre-Charged Stainless Steel Accumulator Tank
that first tank is the one I have. I was charging it to 100 psi and the cut in pressure was 60 psi, so the air valve on the top I should have it pumped to 58 right?
yup, 58psi after making sure it was empty of water and with the tank valve open to the air.
ok thanks atom Ill be sure to do that for my hp aero veg chamber
now to construct my AA rig!