Mk5 - R109

I've only been diving for 15 years, and I just bought a Mk5 - 109, and it is a great setup - don't know if my 109 has been upgraded to balanced or not, but it breathes almost as well as my Mk15 / G200B. I've tried several newer regs over the years, but I can't say for sure any of them breathed better than these old SP's regardless of price.

It's amazing how little good technology changes over time.

Just my humble experience.

The Mk 5 Adjustable was aclassic workshorse reg and the derivative Balanced Adjustable was icing on the cake.

The G250 was derived from the same basic but utilized a MUCH cheaper to produce plastic case with the diver getting the consolation of an adjustable flow vane (that few divers adjust anyway). In terms of second stage design, things pretty much peaked with the G250 and D400.

From that point forward, other than a few advances in sealed diaphragm first stage design, reg design over all has been either stagnant or in decline with most compnaies putting more money into marketing hype on things like the "benefits" of smaller second stages and more and more plastic (cheaper to produce, but oddly more expensive on the dealer shelf) parts than into solid engineering advances.

I also have a Mk5 - R109. I had it upgraded about ten years ago but did select the balanced upgrade at the recommendation of the tech. He stated you would not notice an improvement, I feel he was right. It breathes as good as other balanced regs I used five years ago. Due to it's age, it is not my primary reg, rather a solid backup.

Shows the level of customer support Scubapro provides. To retrofit older equipment to have more modern parts/features. You have to pay for the upgrades. At least you have that option.

Hope it serves you well - Tom

The performance advantage to the balanced poppet upgrade is slight. The Mk 5 and Mk 10 for example are not perfectly balanced (due to the area of the seating edge itself not being compensated for as is the current practice with the Mk 20 and Mk 25) and will experience a drop in IP of 4 to 6 psi as the tank pressure falls from 3300 to 300 psi. So there is some benefit to balancing but not one that a diver would probably notice in the water. There is a very noticeable improvement with an unbalanced fist stage like the Mk 2 or Mk 3 and virtually no difference with the Mk 20, 25, 11, 16, 17 or 18 first stages.

The real benefit is that the upgraded reg will then use the same S-wing poppet and annual service kit as the G200B G250, G250HP, G500, S555 and S600 - which is one of the two most common Sp second stage annual kits around and everyone always has them in stock. The unbalanced duro poppet used in the R109 and G200 is less common and it would be possible to encounter a shop that does not have one in stock as none of the current SP regs use that poppet.

Another significant benefit is that the balanced poppet uses a much lighter spring so the seat does not develop an excessive seating groove as readily over time as can and does occur with the unbalanced R109 with its much heavier spring. So the balanced poppet is much less likely to develop a freeflow issue due to excessive seat engraving over the course of a diving season.

When I take it in the servicing at the dealer, I'll ask them if it's been upgraded. My intent is to use the mk5/109 as a redundant backup, so I'm not sure if an upgraded is in fact worthwhile.

How can you tell what Reg you have...I have several old SP regs--chrome bodies. One of the first stages is a monster block of metal--the other is a more modern configuration.

116fire:

How can you tell what Reg you have...I have several old SP regs--chrome bodies. One of the first stages is a monster block of metal--the other is a more modern configuration.

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Post a photo and someone will be able to ID them for easily.

I just bought a MK5, a G200B, and a 109. It seems each reg I buy is older than the last.

Here's a slight hi-jack, although it does pertain to the idea of reg technology improving, or not. I have a friend who wants to buy a reg that will be able to comfortably tolerate several years between servicing. He's not too concerned about cutting-edge performance, rarely dives deeper than 80 ft, and is excellent with air consumption. I'm torn between recommending a MK2 and a MK5, each with balanced adjustable 2nds. On one hand, the MK2 has fewer parts, and no dynamic o-ring subject to tank pressure. (I finally understood that one once I looked at the Harlow book.) The MK5 seems to have a more robust seat arrangement. So, I guess the question is, if you were stranded on a desert island with unlimited tanks but no repair kits, which reg would you rather have?

116fire:

How can you tell what Reg you have...I have several old SP regs--chrome bodies. One of the first stages is a monster block of metal--the other is a more modern configuration.

Click to expand...

That monster block of metal is a Mk7. The more modern configuration 1sts are likely either a Mk5 (ambient chamber holes are in the cap) or a Mk10 (ambient chamber holes are in the body). The Mk5 and Mk7 may be equipped with light yokes which are not designed to jhandle the pressures of most modern tanks.

The metal 2nd stages are likely either the High Performance 2nd (aka 108 or 080) which lacks an adjustment knob or the Adjustable or Balanced Adjustable (aka 109 or 156) which have an adjustment knob on the side opposite the hose. If you have something that does not match these descriptions (there are others) you will probably need to describe them or post a picture.

mattboy:

So, I guess the question is, if you were stranded on a desert island with unlimited tanks but no repair kits, which reg would you rather have?

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The SP Mk 3, Mk 2, Mk 200, etc are super simple and will go years without an annual service.

But the Mk 10 runs a very close second as does the Conshelf XIV.

Any simple downstream unbalanced poppet regulator is pretty simple and very reliable but most tend to develop leaky seats after a couple years. Most of those seat however can also be flipped getting you another couple years.

The Conshelf second stage (the older all metal Aquarius, Conshelf XII, XIV variety) is however probably the world champ for lenght between servicing without issues.

So...I'd probably want a Conshelf XIV if I were marooned on a desert island with unlimited air and no regulator parts.