1st Stage Reg, Piston vs Diaphram

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leeblackman

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Are there any important differences that I would need to know between a piston and a diaphram first stage regulator, being the new diver that I am. And what does a ballanced reg mean?
 
You may find a balanced reg easier to breathe than an unbalanced reg at depth and when the tank is nearly empty.

You may also find that a piston reg is more expensive to buy but less expensive to maintain.
 
A balanced reg has a design that maintains a constant intermediate pressure (over ambient pressure) which means the air being delivered to the second stage is always at the same pressure ove ambient pressure and allows more preceise tuning of the second stage inhalation effort.

In most cases, it also means the first stage can use a larger orifice and have a higher flow rate which improves performance at depth.

The choices are balanced piston, balanced diaphragm or unbalanced piston.

Unbalanced piston regs are very simple and tend to be inexpensive, but are very reliable and offer enough performance for recreational depths.

Balanced piston regs offer high performance and a fairly low parts count, but most are not environmentally sealed and amny of those that are tend to have fairly complex sealing systems or rely on silicone grease or christolube to fill the ambient chamber.

Diaphragm regs very from ok to excellent in terms of performance and some, but no where near all, are available with dry sealed ambient chambers that make them very well suited for cold water diving.
 
I agree with the above but to help tanslate a little clearer.
Unbalanced regulators do have a change in the breathing when you are low on air and at depth. They are typically the lowest price of a line's regulators and are found in a lot of rentals at dive stores.
Balanced regs are good until the last drop as far as breathing from lower tank pressures and at depth.

Piston regulators need a little more care by the owner when rinsing the first stage as they are unsealed and and could get sand, grit, dirt and whatever in the unsealed portions as water travels through them. This is often a place for unseen salt water corossion for regulators that are not regularly maintained.

Diaphragm regulators are great for colder water as well as warm water and require less maintenance following a dive as the innards are protected from the elements. This makes them ideal for a multitude of diving situations warm or cold.

Realize that no manufacturer can afford to make a bad regulator but some of the features that companies offer on their various regulators such as Oceanic's DVT (Dry Valve technology) on their first stage do have their advantages for the diver as well as the service personnel working on the regulators on their inspections.

Do your research which, by asking on here, has already begun.
 
Not all diaphragm first stages are sealed. Most in fact are not sealed and require about the same rinsing as a piston first stage. All diaphragm first stages (currently in production) are however balanced.
 
Some of the highest performance regulators have been flow through balanced piston type. The Mk V type and it's many clones are examples. Most such units are open to seawater. The spring and internal area of the bore and spring cavity can become contaminated in dirty water or from lack of careful flushing after dives. The current fascination with sealed first stages and cold water diving tend to favor the diaphragm type. N
 
Are there any important differences that I would need to know between a piston and a diaphram first stage regulator, being the new diver that I am. And what does a ballanced reg mean?

Balanced regs are designed so that the supply air pressure acting on the reg is counteracted by re-routing some of the air pressure so that it exerts a force in the opposite direction, thus removing some of the effect of the supply pressure. The effect in diving is that with unbalanced piston 1st stages, as the tank empties the pressure needed to close the valve will be lower, because there's less force from the tank pressure trying to open it. This results in air being sent to the 2nd stage at slightly lower pressure with a near empty tank. That will make 2nd stages a little more resistant to opening, or slightly higher breathing effort. This effect is more noticeable with unbalanced 2nd stages as well.

Balanced vs. unbalanced has absolutely nothing to do with depth. All regs are depth compensating; they would not work otherwise. When people say that unbalanced regs, by design, do not breathe as well at depth they are incorrect. However, there is a higher flow demand on all regs at greater depth, and since most unbalanced regs have lower flow rates, you'll notice any limitations in flow in any reg at depth.

If you find yourself at significant depth with very little air (say less than 500PSI at 100ft) an unbalanced piston reg (like the SP MK2) will deliver noticeably less air than a higher flow balanced reg like the MK25, or many others. This is hardly a purely negative attribute, because if you're that deep with that little air, chances are you could use a "reminder" that it's time to head up. There was recently a thread about a guy who was thrilled with his great improvement in air consumption when he noticed late in a dive that he still had 900PSI. A few minutes later, he suddenly couldn't get any air; his SPG had stopped working and he had no idea he was dangerously low on air. An unbalanced piston 1st stage would probably have prevented that.

The debate about piston vs diaphragm regs is one of the longest running discussions on SB. There are excellent regs of both designs; there are advantages to both designs, and there is a wide range of quality and performance among regs of each design. In short, there are good piston regs and not-so-good piston regs, and exactly the same is true with diaphragm.

I'm certain that reg performance in the real world of recreational diving has much more to do with how well the reg is maintained and adjusted. I have a friend who recently bought a sherwood SR1, which is touted as one of the easiest breathing regs on the market. We put the brand new reg on a tank and found it had a higher cracking effort than my MK2/R190, which is much lower flow, "entry level" reg, but maintained and tuned well. Obviously the dealer at which he bought the SR1 did not bother to tune the reg at all.
 
https://www.shearwater.com/products/perdix-ai/

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