Possible reasons:
(1) The pressure of a single cylinder cannot be increased.
(2) The air tank has less air.
(3) The air tank has less air.
(4) The lower end of the air tank has more sediment, resulting in a smaller air volume.
Troubleshooting:
(1) Stop the pump, open the valve below the air tank to release the slurry, and then replenish the air by yourself.
(2) Remove the pressure gauge connector on the upper end of the air tank and rinse the shower air tank with pressure water.