TUSA

TUSA RS-790 (DIN)

TUSA's environmentally sealed, cold-water-ready balanced diaphragm reg built around a dry ambient pressure chamber and anti-freeze system.

Environmentally sealed, cold-water rated

Sealed first stage keeps water and ice crystals out of the internal mechanism, the standard for diving below 50°F/10°C.

TUSA RS-790 (DIN)
4.1Comparison Score
$529
Buy on Amazon
Released2012
First stagediaphragm
BalancedYes
Environmentally sealedYes
Cold-water ratedYes
ConnectionDIN
Max pressure300 bar
HP / LP ports2 / 4
Adjustable 2nd stageYes
Weight850g
Nitrox-ready (EAN40)Yes
Octo includedNo

"HP / LP ports" is the number of high-pressure and low-pressure ports on the first stage, which caps how many accessories (transmitter, SPG, inflator, second second-stage) you can run at once.

Pros
  • Environmentally sealed R-700 first stage with a dry ambient pressure chamber and anti-freeze system, cold-water rated out of the box (no separate kit needed, unlike the RS-681 or RS-609)
  • Two of the four LP ports are TUSA's high-flow spec, rated for up to 15% more airflow than the standard ports, the same high-flow spec used on the RS-1001
  • Factory nitrox compatible up to 40% EAN without a separate O2 service
Cons
  • S-90 second-stage case is composite rather than metal, so it doesn't feel as premium in hand as some competitors at this price
  • TUSA doesn't publish an official weight spec for the R-700/S-90 combo on its own site
  • Sold as a first-and-second-stage set only, no octopus/backup second stage included
Diver community sentiment
Mostly positive

Divers on Scubaboard describe the RS-790 as a solid, reliable, no-drama regulator rather than a top-tier performer, several times summarized as "a good regulator... far from the bottom." One instructor with 500+ dives reported using a pair in the Great Lakes for three years with no problems. A recurring theme is that the RS-790's internals are essentially the same as the Scubapro MK17/S550, so parts and service kits are interchangeable. In head-to-head threads against the Atomic Z3, posters tended to recommend the Atomic instead for a modest premium, citing better hose routing and an adjustable second stage, plus a longer service interval. No complaints about free-flow or reliability failures turned up.

Scubaboard: RS-790 owner feedback threadScubaboard: RS-790 vs Atomic Z3 comparisonScubaboard: shared first-stage design with Scubapro MK17

Summarized from public forum discussion (Scubaboard, Reddit, and similar), not a survey we ran ourselves. See the linked threads for the original conversations.

The RS-790 is TUSA’s dedicated cold- and contaminated-water specialist, built around the same environmentally sealed, dry-chamber R-700 first stage design TUSA later carried into the RS-1001. It’s sold in both DIN and yoke configurations (this entry covers the DIN version) and sits alongside the RS-1001 as one of TUSA’s higher-tier balanced diaphragm regs, rather than a step below the RS-681.