How to lower pressure in air compressor?

Adjust the pressure switch, or replace it if it is non-adjustable.

There are two approaches. The choice depends on your air use (it makes sense to use both approaches simultaneously).

Approach 1. Look into the cover on your pressure regulator (usually located close to air pressure gauge), it is a little box. Take off the cover and you will see adjusting screws, adjust them.

Approach 2. Add a pressure regulator to the output of the compressor, so that even though pressure inside the compressor changes, pressure of the air going to the tools stays constant.

Like I think Ignor meant to say you could either adjust the pressure switch or and add a regulator. If you want to drop the pressure only marginally then I suggest you adjust the switch by reducing the preload on the main adjustment spring. If you want to drop the pressure by a crap load, or if you find yourself making frequent adjustments, then just add a regulator to the pressure output. Adjusting the pressure switch very low will cause frequent start and stops which are not good to do.

Get an air pressure regulator and plumb it into the main line going out to your shop equipment, then you can turn down the pressure to the shop lines wherever you want, and fast. It should have an air filter in front of it, jut in case any dirt or rust gets out of the compressor receiver tank.

If the compressor runs fine as-is, do NOT lower the pressure in the receiver tank by resetting the pressure switch - this lowers the volume of air stored in the tank, and will have the compressor cycling on too often.

You don't want the compressor to cycle more than 5 or 6 times an hour unless you are sandblasting or using a LOT of air for a short period - too many starts per hour over the long term can damage the starting circuit in the electric motor, and the repeated starting surges play hell with your demand load on commercial power services.

If your shop uses a lot of air all day, you may want to upgrade to a 'screw type' rotary compressor, which works like a Roots Supercharger

- during the work day when you use a lot of air they leave the motor running all day and the control system modulates the compressor section from 'off' to 'wide open' to match the loads.

This is the same tech used in the towable compressors used for jackhammers, except they also throttle the engine down to save fuel when the compressor section is unloaded.

-->--