Updated: Aug 9, 2022
Often it is the simplest of things that can cause problems, such as basic pressure adjustments. For proper function, a dental delivery system needs the correct air and water pressure supplied to the unit from the source (junction box). The main pressure must be correct. The gauge on the front of your unit is for the handpiece drive air pressure and is not what you want to check you need to check the gauges in your junction box (if you have bottles as the sole source of water, check for a gauge on the bottle).
Typical main pressure settings are 80 psi for the air, and 40 psi for the water. The key is that the air pressure is at least double the water pressure. Given the greater density, water pressure must be dramatically lower as it is air activated.
To adjust the pressure, you'll need to find your junction box and the regulators therein. There are usually gauges attached to the regulators to indicate the pressure settings. To change the pressure, there is going to be some sort of knob or screw. Before turning the pressure adjustment, have an assistant depress and hold down the buttons on the air water syringe. You can't adjust the pressure unless you have an "active flow" i.e. the air and water must be moving. If you attempt to adjust the pressure while static, it simply won't take effect. While air and water are flowing out of the syringe, you can turn the adjustment as appropriate until the pressure setting is as desired.
Most knobs are marked with the direction to turn to adjust the pressure, but it is usually a matter of turning the knob IN (clockwise) to increase the pressure and OUT (counter-clockwise) to decrease the pressure. This is somewhat counter-intuitive. "In" to "INcrease" is a handy mnemonic device to keep this straight.
The attached photo shows an a-dec junction box with the air regulator called out. You can see a sticker with the letter "A" indicating this is for air. I've also called out the cylindrical filter housing. These filters are used in many brands of equipment and should be checked quarterly and replaced as necessary or annually at a minimum. Often a clogged filter can lead to inadequate pressure or pressure dropping off dramatically after a short time.