I had a Makita at the rock farm, it just showed up one day from the boss, could have been kickbacks involved with the supplier :lol:. It took some experimentation and practice to get the pump to regain it's suction after running the previous tube empty.
The usually have a bleed valve to get the air out. I had great luck selling the DeWalts. A lot of farm implement techs greasing combines gave them a good test.