TRUETEXAN
Contributor
I would be interested in hearing everyones preference on first stages and whether or not they like piston or diaphram and why.
Piston vs. Diaphragm
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Hi TRUETEXAN,
I like them both, provided they are high quality & well-performing.
Here's a little piece that appeared in my "Ask RSD" column in the Nov/Dec 1999 issue of "Rodale's Scuba Diving":
"Which first stage regulator design is better -- piston or diaphragm?
In considering the piston v diaphragm issue, remember that the quality of design, material and workmanship is more important than the type of first stage. If you experiment with the best examples of piston and diaphragm models under normal conditions, you are not likely to notice any appreciable difference in terms of breathability, reliability or durability. Divers who do very cold and/or dirty water sometimes prefer the diaphragm type as it may offer some extra protection against freeze up and contamination since it does not allow water into sections of the first stage, but piston types can be protected as well, such as by factory or after market environmental sealing and dry bleed systems. Piston models are, on average, mechanically simpler, making them easier, although not necessarily cheaper, to service than diaphragm regs.
A number of major manufacturers produce both piston & diaphragm designs, and there is a wide choice of excellent models of both designs. Before buying, read reviews, ask other divers and try out those you are seriously interested in whenever possible."
Hope you found this helpful.
DocVikingo
I like them both, provided they are high quality & well-performing.
Here's a little piece that appeared in my "Ask RSD" column in the Nov/Dec 1999 issue of "Rodale's Scuba Diving":
"Which first stage regulator design is better -- piston or diaphragm?
In considering the piston v diaphragm issue, remember that the quality of design, material and workmanship is more important than the type of first stage. If you experiment with the best examples of piston and diaphragm models under normal conditions, you are not likely to notice any appreciable difference in terms of breathability, reliability or durability. Divers who do very cold and/or dirty water sometimes prefer the diaphragm type as it may offer some extra protection against freeze up and contamination since it does not allow water into sections of the first stage, but piston types can be protected as well, such as by factory or after market environmental sealing and dry bleed systems. Piston models are, on average, mechanically simpler, making them easier, although not necessarily cheaper, to service than diaphragm regs.
A number of major manufacturers produce both piston & diaphragm designs, and there is a wide choice of excellent models of both designs. Before buying, read reviews, ask other divers and try out those you are seriously interested in whenever possible."
Hope you found this helpful.
DocVikingo
Relative popularity of these two types of first stage regulator have waxed and waned, primarily due to marketing. As stated above, either will perform adequately as long as the quality is there. The mechanical differences, since they are substantial, would be of interest to someone interested in doing their own maintenance; otherwise differences are moot. There are variations of the diaphragm and piston. The type of piston used in a quality reg is the "flow through" type. At this point I should also mention a third type of first stage manufactured by Sherwood. This piston reg features a floating valve seat and is different from the other two. However, quality is first rate if a bit complex.
Scubapro has the most experience in producing pistons. However, they are no longer constructed with only one moving part as in days of yore. User maintenance is probably not practical unless you have a complete schematic and access to parts. The parts themselves are proprietary, even the O rings, and cannot be substituted.
The foregoing also apply to diaphragm regs with exceptions. Several manufacturers have long experience in making these including Dacor, Mares, Aqualung, Poseiden and Apeks. Scubapro also makes a quality diaphragm. The diaphragm regs have about the same number of parts as modern piston regs. However, the parts are very small and require care in handling and assembly. Aqualung parts are easiest to obtain. Some, like O rings, can be generic.
Both types require some special tool or tools depending on model. These can be spanners, circlip pliers, dental tools, etc.
Normally, I use a Scubapro piston reg. However, I also own a USD Conshelf which is a diaphragm type. For most diving, there is no practical difference. However, for extreme exposure, cold water and such, the Conshelf first stage would be my choice.
To summarize, the differences and preferences are mostly of interest to the technician. Parts availability may become an issue to the traveling diver, otherwise the differences are slight. If forced to choose for all around usefulness, the diaphragm may have a slight edge.
Scubapro has the most experience in producing pistons. However, they are no longer constructed with only one moving part as in days of yore. User maintenance is probably not practical unless you have a complete schematic and access to parts. The parts themselves are proprietary, even the O rings, and cannot be substituted.
The foregoing also apply to diaphragm regs with exceptions. Several manufacturers have long experience in making these including Dacor, Mares, Aqualung, Poseiden and Apeks. Scubapro also makes a quality diaphragm. The diaphragm regs have about the same number of parts as modern piston regs. However, the parts are very small and require care in handling and assembly. Aqualung parts are easiest to obtain. Some, like O rings, can be generic.
Both types require some special tool or tools depending on model. These can be spanners, circlip pliers, dental tools, etc.
Normally, I use a Scubapro piston reg. However, I also own a USD Conshelf which is a diaphragm type. For most diving, there is no practical difference. However, for extreme exposure, cold water and such, the Conshelf first stage would be my choice.
To summarize, the differences and preferences are mostly of interest to the technician. Parts availability may become an issue to the traveling diver, otherwise the differences are slight. If forced to choose for all around usefulness, the diaphragm may have a slight edge.
sinners
Guest
Balanced Piston - any good or just myth?
Your opinions please....
Your opinions please....
chuckrt
Contributor
Diver0001,
I have used a piston(bal) in all water conditions ans temps. Most of the people I dive with also use them, SP MK20/25. They get used in winter with water temps at 35-36 deg. just don't breathe with out being in the water.
chuckrt
I have used a piston(bal) in all water conditions ans temps. Most of the people I dive with also use them, SP MK20/25. They get used in winter with water temps at 35-36 deg. just don't breathe with out being in the water.
chuckrt
I have a Sherwood piston that I use as an octopus but it's dry sealed. I dive in water around or slightly under the freezing point (amazingly this is possible, I usually clock several dives a year in -1 or -2 celsius) for several months of the year and I just don't like the idea of having nearly freezing water inside my first stage. You probably have more nerve than I do
R..
What is the Diffrence between a Reg with a Piston and a Diaphragm. Which one is better? Which is more reliable? Which one is easy to mantain. I am looking at geting the Scuba Pro Mk2 Plus/R190 Regulator.
I will be diving in warm waters off the Ga coast And Fl coast.
I will be diving in warm waters off the Ga coast And Fl coast.
DIR Tec Diver
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Since you will be in warm waters you will probably have good times with your first stage, but the R190 is not really a good option. It is a cheap reg, big, bulky and prone to free flow.
Diaphram regs are more sensitive and generally give better performance. They are also necessary for cold water diving to prevent freezing of the moving parts found in piston regs. Even though some piston regs come with cold water kits they rarely work (I know from experience).
It comes down to the types of diving you will do and your personal preferance. I personally prefer the diaphram regs where especially when I am deep I notice the differences in performance and since I dive in really cold water a lot the safety aspect is there as well.
In regards to your second stages get better than the R190, you will be glad you did
Diaphram regs are more sensitive and generally give better performance. They are also necessary for cold water diving to prevent freezing of the moving parts found in piston regs. Even though some piston regs come with cold water kits they rarely work (I know from experience).
It comes down to the types of diving you will do and your personal preferance. I personally prefer the diaphram regs where especially when I am deep I notice the differences in performance and since I dive in really cold water a lot the safety aspect is there as well.
In regards to your second stages get better than the R190, you will be glad you did
I have to give a dissenting opinion here. I dive with piston regs and feel that they offer advantages in terms of both flow rate and performance and the freeze issue has been a non issue with me.
I dive in water in the low thirties in winter and in the mid to upper forties at depth in summer and have not had a problem with the Scubapro MK 3, MK 10, MK 15 or more recently the MK 20 or Mk 25 first stages.
The TIS kit (Thermal Insulating System) used by Scubapro is not, in my opinion, as effective as the SPEC (Silicone Protected Environmental Chamber) kits used on their older MK, 3, MK5, MK 9, MK 10, or MK 15, but it seems to work for me.
The piston reg is also bullet proof with essentially one moving part (the piston) and very few critical o-rings subject to wear (two, 1 high pressure and 1 low pressure, on most designs) from the moving piston. They are easy to maintain, require minimal service and are easy work on for annual service.
In terms of mechanical relaibility, they have a distinct advantage over more complex diaphragm first stages and will maintain peak performance bewteen regularly scheduled servicing with no potential for degradation caused by stiffening rubber diaphragms, etc.
Some divers do have problems with the newer MK 20 and 25 in cold water, but other don't and I think it relates to breathing rates or patterns. With the older MK 3 or MK 10, I can fill a 200 lb lift bag at 140' in 40 degree water and not freeze one up.
But if you are diving warm water, I would choose a good piston reg hands down over a diaphragm reg just for the increased reliability and performance.
The MK2 is basically a redesigned MK 3 that is DIn compatible and has an extra LP port. It is not really a great performer at depth but is simple and relaible.
The R190 is not balanced and if not adjusted properly can freeflow, particularly with an unbalanced first stage like the MK 2. If you get one, it needs to be adjusted for minimum breathing effort on a full tank. The intermediate pressure varies a bit from full to empty tank on an unbalanced reg as the high pressure air from the tank acts directly on the seat mounted on the bottom of the piston.
What often happens is the reg gets adjusted on a shop air tank at far less than 3300 psi. the result is that when attached to a full tank, the intermediate pressure is slightly higher than when the second stage was adjusted and the reg then has a slight freeflow. (Some techs are really poor at their job and the reg unfortunately gets blamed) With proper adjustment freeflow is not an issue but, being unbalanced, it will breath slightly harder at low tank pressures.
The R380 is a balanced second stage and offers consistent performance with varying intermediate pressure, but I would go with a G250. It's balanced, adjustable, bullet proof, and well matched to the Mk 25 first stage. Although it is not marketed this way by Scubapro, it also works well with the Mk 2 first stage and if set up properly the G250's adjustment allows you to maintain minimum breathing effort as tank pressure falls.
With either a G250 or an R380, you would have great performance at moderate depths for relatively small bucks.
I dive in water in the low thirties in winter and in the mid to upper forties at depth in summer and have not had a problem with the Scubapro MK 3, MK 10, MK 15 or more recently the MK 20 or Mk 25 first stages.
The TIS kit (Thermal Insulating System) used by Scubapro is not, in my opinion, as effective as the SPEC (Silicone Protected Environmental Chamber) kits used on their older MK, 3, MK5, MK 9, MK 10, or MK 15, but it seems to work for me.
The piston reg is also bullet proof with essentially one moving part (the piston) and very few critical o-rings subject to wear (two, 1 high pressure and 1 low pressure, on most designs) from the moving piston. They are easy to maintain, require minimal service and are easy work on for annual service.
In terms of mechanical relaibility, they have a distinct advantage over more complex diaphragm first stages and will maintain peak performance bewteen regularly scheduled servicing with no potential for degradation caused by stiffening rubber diaphragms, etc.
Some divers do have problems with the newer MK 20 and 25 in cold water, but other don't and I think it relates to breathing rates or patterns. With the older MK 3 or MK 10, I can fill a 200 lb lift bag at 140' in 40 degree water and not freeze one up.
But if you are diving warm water, I would choose a good piston reg hands down over a diaphragm reg just for the increased reliability and performance.
The MK2 is basically a redesigned MK 3 that is DIn compatible and has an extra LP port. It is not really a great performer at depth but is simple and relaible.
The R190 is not balanced and if not adjusted properly can freeflow, particularly with an unbalanced first stage like the MK 2. If you get one, it needs to be adjusted for minimum breathing effort on a full tank. The intermediate pressure varies a bit from full to empty tank on an unbalanced reg as the high pressure air from the tank acts directly on the seat mounted on the bottom of the piston.
What often happens is the reg gets adjusted on a shop air tank at far less than 3300 psi. the result is that when attached to a full tank, the intermediate pressure is slightly higher than when the second stage was adjusted and the reg then has a slight freeflow. (Some techs are really poor at their job and the reg unfortunately gets blamed) With proper adjustment freeflow is not an issue but, being unbalanced, it will breath slightly harder at low tank pressures.
The R380 is a balanced second stage and offers consistent performance with varying intermediate pressure, but I would go with a G250. It's balanced, adjustable, bullet proof, and well matched to the Mk 25 first stage. Although it is not marketed this way by Scubapro, it also works well with the Mk 2 first stage and if set up properly the G250's adjustment allows you to maintain minimum breathing effort as tank pressure falls.
With either a G250 or an R380, you would have great performance at moderate depths for relatively small bucks.
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