Ask Joe & Larry

What does it mean to have a balanced or non-balanced regulator?

Larry:   When people talk about balanced and non-balanced regulators - they are normally referring to the first stage (the part that screws onto the tank). The diagram shows a balanced 1st Stage. A first stage's job is to take tank pressure (3000 psi) and knock it down to 145 psi over ambient pressure. That means if you go down 33 feet, it actually increases the pressure to about 160, and 175 psi at 66 feet etc. It does this by have either a diaphragm that has water pressure on it that transfers the pressure to the internal parts.


If we take a look at the reg diagram, we see the High Pressure air coming in (HP) and if flows through the little filter (shown in blue) and into the HP Chamber of the 1st stage. The high pressure air is shown in red. The hose that goes to your 2nd stage regulator is attached where it says LP (low pressure - or 145 psi). When you inhale, that pressure drops which then sucks down the black diaphragm which pushes on that blue pin (near the middle) which goes into that black and yellow thingy... known as a seat. Called that because it seats against some sharp pointed brass to block the air flow when you're not inhaling. The black end of the seat is rubber, and that gets cut up in time by the pointy brass part and so gets replaced once a year when you do service.

I know this is a bit confusing - but hang in there... See where the red arrow is pointing?? This is the balance chamber. You can see that they have to drill a hole from the LP area over to that... That's because to achieve a balanced condition it is essential that both ends of the valve head be exposed to identical pressure. If you don't have that balance chamber, you'd have an unbalanced regulator.

An unbalanced regulator suffers from the problem that when tank pressure gets low - around 500 psi, it starts getting harder and harder to breath. Some say, "No big deal - gives you a nice warning you're getting low on air, and you should be going up by then anyway". With a balanced regulator you will get the best performance until tank pressure drops to the 145 over ambient - the intermediate or low pressure.

Ok, now that we've got the air heading down the hose at 145 psi, the air then tries to get to the second stage. I say tries since it stops just shy at something called a 2nd stage seat. Basically a piece of rubber on a little piece of metal or plastic. A sharp metal pipe is at the end of the hose that hits this rubber - the pressure trying to push the rubber away from the pipe... but it can't because there is a spring balanced out to the same pressure behind it. Then when you hit the purge, or inhale, a big rubber diaphragm in the second stage bends in, hitting a lever, that is attached to the back end of the seat which then pulls away from the pipe and allows the air to rush by into the second stage and out the mouthpiece.

Now if you want to get fancy, you can put an external adjustment on this spring tension and viola' you've got an adjustable second stage. Some companies like have regs like the top of the line Aeris Atmos Pro that use something called a pneumatically balanced 2nd stage, which basically means there is a hole in the seat, and a balance chamber behind it that will then have the same pressure air as is coming down the hose. This means they can use a lighter spring and that should in turn make the breathing easier. Check out the Aeris Atmos Pro for an example of an excellent pneumatically balanced second stage that is also adjustable.