How does a balanced scuba diving regulator work? That can be a complicated question that I’m going to try and answer as simply as possible.
Forget right now whether we are talking about a piston type diving regulator or a diaphragm type. The principle is the same even if the actual hardware is different.
The purpose of The first stage of a scuba regulator is to take the high pressure in the tank, which you can’t breathe, and reduce it into low pressure air which you can.
A balanced regulator keeps the pressure of this breathable air the same, 145-150 psi above ambient pressure, no matter what depth you are at or what the pressure of the air is in your tank.
When you go up or down the pressure of the water around you (ambient pressure) changes, and as you breathe the pressure you have in your tank drops. A balanced diving regulator should “breathe” the same no matter what.
Balanced Piston Scuba Diving Regulator
Here is a simplified balanced piston style scuba regulator diagram.
At rest the pressure in the Intermediate chamber is greater than the Ambient water pressure. This is pushing the piston to the right, against the spring and seating the valve firmly, cutting off the HP air flow from your tank.
When you take a breath trough the second stage, the pressure in the intermediate chamber drops and the ambient water pressure and spring push the piston to the left, unseating the valve and letting air flow through the valve from the HP chamber.
When you stop taking air from the second stage, the pressure in the intermediate chamber rises and works to push the piston back to the right, seating the valve and stopping the air flow.