Why do piston regs cost more than diaphragm regs?

[Eric Sedletzky]

... and why exactly? Honest question. I've heard people say they are "better" for years, but I've never heard a solid argument as to why.

I’m a piston fan myself. And not because of a piston reg being my first purchase or some other sentimental reason. I’m looking at the engineering and simplicity, they are a simpler and more fail proof design. People don’t like them because water enters the ambient chamber and in order to seal them involves a lot of messy grease packing and a way to keep out salt water with a sealing band and/or a dry chamber design etc. But the basic design is what I like. Scubapro has gotten away from trying to seal them and just went back to an open breathable design which is simpler and better. I have a buddy who works in a very busy shop in the LA area. They are a scubapro shop and do a lot of services on UCLA diving program regs which are all Scubapro MK25’s. They don’t ever rinse anything, those regs are abused, thrown around, used in salt, pool, whatever. They come in all crusty and nasty with green corrosion inside and out. He says they clean right up, he rebuilds them, they hold IP, work great and they’re on their way. Maybe it’s the brand? IDK, but when I heard this I though there is nothing to worry about with salt exposure. They’re made for it. I soak mine anyway overnight attached to a tank and pressurized so I’m way ahead.
I don’t like all the soft parts in diaphragm regs. I don’t like the idea of a diaphragm flexing away and holding IP pressure back. I don’t like the way the HP seats are designed on a lot of models. They mount a nylon seat onto a base with a stem and I have heard of them suddenly having a catastrophic failure where IP increases so fast the second stages don’t have time to freefow and the pressure blows out the diaphragm on the first stage. I think diaphragms are overly complicated with two springs, a seat made out of two materials not including adhesive, a pin, a rubber diaphragm, a balancing chamber.
With piston regs you have one moving part, the piston. If you count the one spring then two moving parts. The piston seat (one material) is captured in a carrier and thus would be very difficult to break down catastrophically. There is no diaphragm to blow out or tear. They by design are a much more solid and simpler reg. Simple is good. If the HP seat had a catastrophic breakdown/meltdown sending the IP through the roof instantly then it would have to be very old and brittle or perhaps some aftermarket one that was made out of a material that was completely inadequate for that purpose.
But I’m still confused as to why a simpler design with less parts is more money. Not that I really care but I was just wondering for conversation sake.

 

[BoltSnap]

I’m a piston fan myself. And not because of a piston reg being my first purchase or some other sentimental reason. I’m looking at the engineering and simplicity, they are a simpler and more fail proof design. People don’t like them because water enters the ambient chamber and in order to seal them involves a lot of messy grease packing and a way to keep out salt water with a sealing band and/or a dry chamber design etc. But the basic design is what I like. Scubapro has gotten away from trying to seal them and just went back to an open breathable design which is simpler and better. I have a buddy who works in a very busy shop in the LA area. They are a scubapro shop and do a lot of services on UCLA diving program regs which are all Scubapro MK25’s. They don’t ever rinse anything, those regs are abused, thrown around, used in salt, pool, whatever. They come in all crusty and nasty with green corrosion inside and out. He says they clean right up, he rebuilds them, they hold IP, work great and they’re on their way. Maybe it’s the brand? IDK, but when I heard this I though there is nothing to worry about with salt exposure. They’re made for it. I soak mine anyway overnight attached to a tank and pressurized so I’m way ahead.
I don’t like all the soft parts in diaphragm regs. I don’t like the idea of a diaphragm flexing away and holding IP pressure back. I don’t like the way the HP seats are designed on a lot of models. They mount a nylon seat onto a base with a stem and I have heard of them suddenly having s catastrophic failure where IP increases so fast the second stages don’t have time to freefow and the pressure blows out the diaphragm on the first stage. I think diaphragms are overly complicated with two springs, a seat, a pin, a rubber diaphragm, a balancing chamber.
With piston regs you have one moving part, the piston. If you count the one spring then two moving parts. The piston seat is captured in a carrier and thus would be very difficult to break down catastrophically. There is no diaphragm to blow out or tear. They by design are a much more solid and simpler reg. Simple is good. If the HP seat had a catastrophic breakdown/meltdown sending the IP through the roof instantly then it would have to be very old and brittle or perhaps some aftermarket one that was made out of a material that was completely inadequate for that purpose.
But I’m still confused as to why a simpler design with less parts is more money. Not that I really care but I was just wondering for conversation sake.

Despite the big hoopla about water entering the intermediate chamber some folks make, yet one of the most reliable first stages that has been in the market for almost 60 years is the SP MK2 first stage. A very simple piston first stage. I don't know of any other first stage that has been in the market for this long while maintaining it's reputation for reliability and simplicity.

 

[jborg]

Maybe the Poseidon Cyklon 1st stage, which is also about 60 years old at this point. It’s a diaphragm design, though…

 

[Divin'Papaw]

I’m a piston fan myself. And not because of a piston reg being my first purchase or some other sentimental reason. I’m looking at the engineering and simplicity, they are a simpler and more fail proof design. People don’t like them because water enters the ambient chamber and in order to seal them involves a lot of messy grease packing and a way to keep out salt water with a sealing band and/or a dry chamber design etc. But the basic design is what I like. Scubapro has gotten away from trying to seal them and just went back to an open breathable design which is simpler and better. I have a buddy who works in a very busy shop in the LA area. They are a scubapro shop and do a lot of services on UCLA diving program regs which are all Scubapro MK25’s. They don’t ever rinse anything, those regs are abused, thrown around, used in salt, pool, whatever. They come in all crusty and nasty with green corrosion inside and out. He says they clean right up, he rebuilds them, they hold IP, work great and they’re on their way. Maybe it’s the brand? IDK, but when I heard this I though there is nothing to worry about with salt exposure. They’re made for it. I soak mine anyway overnight attached to a tank and pressurized so I’m way ahead.
I don’t like all the soft parts in diaphragm regs. I don’t like the idea of a diaphragm flexing away and holding IP pressure back. I don’t like the way the HP seats are designed on a lot of models. They mount a nylon seat onto a base with a stem and I have heard of them suddenly having a catastrophic failure where IP increases so fast the second stages don’t have time to freefow and the pressure blows out the diaphragm on the first stage. I think diaphragms are overly complicated with two springs, a seat made out of two materials not including adhesive, a pin, a rubber diaphragm, a balancing chamber.
With piston regs you have one moving part, the piston. If you count the one spring then two moving parts. The piston seat (one material) is captured in a carrier and thus would be very difficult to break down catastrophically. There is no diaphragm to blow out or tear. They by design are a much more solid and simpler reg. Simple is good. If the HP seat had a catastrophic breakdown/meltdown sending the IP through the roof instantly then it would have to be very old and brittle or perhaps some aftermarket one that was made out of a material that was completely inadequate for that purpose.
But I’m still confused as to why a simpler design with less parts is more money. Not that I really care but I was just wondering for conversation sake.

Ok so I hear ‘simpler’. Not sure how any of what you state makes them better. Not at all criticizing your argument or your desire to use piston regs. But ‘simpler’ doesn’t necessarily equate to better IMO. I’ve been diving sealed diaphram regs for 17+ years with zero issues caused by their ‘complexity’. YMMV.

 

[Divin'Papaw]

deleted duplicate post

 

[Shabaday]

I had a Cyklon and Odin first stage....over 30 years they have been just fine...I have mostly diaphragm first stages...SP Mk17 evo, SP Mk19 evo, Apeks XTX 200....I do have two Atomic ST1's with sealed first stages...Haven't had any major issues with either...I got into diaphragm first stages when doing COLD brrrrr water diving

 

[BoltSnap]

Maybe the Poseidon Cyklon 1st stage, which is also about 60 years old at this point. It’s a diaphragm design, though…

Is it still in production today?

 

[jborg]

Is it still in production today?

Yup. Though probably some details and materials have changed along the way, it’s been a while.

 

[Eric Sedletzky]

Despite the big hoopla about water entering the intermediate chamber some folks make, yet one of the most reliable first stages that has been in the market for almost 60 years is the SP MK2 first stage. A very simple piston first stage. I don't know of any other first stage that has been in the market for this long while maintaining it's reputation for reliability and simplicity.

The MK2 is my desert island reg. If I was stranded on a desert island the MK2 would be my choice.
In fact, if I didn’t get suckered into buying that MK20 by the hot shot salesman I probably would have bought the MK2 and been happy. But I can’t complain about the MK20, it’s been an excellent reg and going for 25 years now, no problems, no creep, perfect.
The only diaphragm reg I have is a Conshelf (actually two) and I can’t complain about them either.

 

[MrVegas]

Are pistons more expensive, though? There are inexpensive unbalanced pistons out there (Edge\Sea Elite, Cressi, Oceanic, Tusa) and the Scubapro Mk2 is lower priced than any diaphragm regs in the Scubapro line, isn't it? Sherwood has balanced pistons designed for cold water that are considerably less expensive than the Mk25.

The Mk25-style designs do have the swivel turret and extra ports and I assume there are also some design differences in the second stage. From what I can tell, unbalanced pistons are usually the cheapest, followed by the diaphragm designs, followed by the balanced pistons. I usually rent gear for salt water diving, and the regs are almost always unbalanced pistons. I will admit, the only time I ever said "wow, that reg breathes great" was a few years back when I rented a Sherwood balanced piston from a local quarry. Of course, it might just have been tuned perfectly, too.