You have to have pressure on the sand in the pot top (to push sand down), you have to have a valve ( at the bottom) to regulate the amount of sand coming out to nozzle. there should be a little less pressure pushing the sand down and an more on the nozzle to help suck the sand into the hose. Remember, more pressure the harder it cuts and , more sand, less cutting and heat it will create on the part. Your air supply has to be dry or it'll cause the sand to ball up. You really need a receiver tank to give the air time to let the moisture steal out. intake from air supply on top, discharge on top a drain **** on the bottom open just a little to help keep the moisture running out. It take a lot of air flow and pressure (80 psi or better) to sand blast.