MK20 -How cold is too cold?

[Benthos]

During periods of strong upwelling I occasionally encounter sea water temperatures of 38'F at depth. Temperatures are more typically in the 40-50 range, with air temps in the 60's. I recently heard a report about a second stage free flow causing a first stage freeze up at similar temperatures.

Would anyone feel they need a sealed diaphragm like an MK17 for 38'F water or is the MK20 just fine?

What do people consider the cut off for salt vs. fresh water?

Opinions?

Thx.

RT

 

[DA Aquamaster]

It depends. I have used Mk 20's and Mk 25's successfully with D400 second stages in 35-38 degree water at 150 ft depths. However, I have seen Mk 20 and Mk 25 first stages used with the S600 second stage freeze on a frequent basis in the same conditions.

If you use low pressure tanks (2250-2640 psi), a good cold water second stage (D400, G250HP, X650, Balanced Adjustable) and good cold water technique the Mk 20 may work well for you at temps below 40-45 degrees. But...I switched to the Mk 17 because "may" just did not leave me feeling very inspired. And in fact prior to the release of the Mk 17, I reverted to using the SPEC system on my Mk 20's as it is much more relaible in cold water than the TIS system.

 

[spectrum]

FWIW I have seen 42F referenced a few times as the point where you want to be considering a cold water rated system.