diaphragm or piston 1st stage?

[watchoutheyspit]

Would anyone care to explain to me the advantages and disadvantages of a diaphragm & piston 1st stages?

I checked down 10 pages in this section and saw no threads relating to it.

 

[DA Aquamaster]

Piston stages tend to be simpler. Unbalanced "flow by" piston designs are dirt simple, super reliable and have an extremely low parts count. Performance is usually not stellar though and flow rate is virtually always less than 100 SCFM.

Balanced piston designs tend to be very high performance with relatively low parts counts. They are generally simple and reliable but are either not environmentally sealed or rely on silicone filled ambient chambers for cold water protection. Or in the case of newer SP regs on a more involved anti-freeze protection system. A few designs use air rilled ambient chambers with check valves and schraeder valves to maintain ambient pressure and a a dry chamber. At that point though parts count is as high or higher than most diaphragm designs.

Unbalanced diaphragms are exceedingly rare as it is very easy to balance the seat carrier and there is no reason not to do it. Balanced diaphragms offer average to excellent performance but usually not the 200 to 300 SCFM flow rates possible with some balanced piston designs. They have higher parts counts on average and performance can deteriorate a bit more over time due to the dipahragm stiffening with age and use. They are easier to environmentally seal but some still rely on silicone or alcohol filled environmental chambers and they can leak. Some balanced diaphragm stages are also not environmentally sealed even though many divers almost automatically assume a diaphragm second stage is envrionmentally sealed.

Either way, a good quality reg of either design will serve you well.

 

[watchoutheyspit]

Thanks DA Aquamaster !

 

[crpntr133]

There are also many threads that discuss this even further. For the most part, what DA Aquamaster said.
You will find that most cold water divers will use a diaphram reg.