Does anybody know the flow rate of the mk5 and mk10?
I was wondering how close it was to the mk20's and mk25's.
I was wondering how close it was to the mk20's and mk25's.
Scubapro Regs... What's the difference? Which one to get?
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I am working from memory here (about 20 years worth) but the Mk 10 has a flow rate around 110 SCFM and the flow rates stays pretty constant as tank pressure falls to 300 psi.
The MK 5's flow rate is very slightly less at high tank pressures (around 100-105 SCFM) but falls off to around 65-67 SCFM at low tank pressures. The Mk 5 does however have a large diameter piston head (similar to the Mk 15, 20 and 25) and is very responsive, so I could never tell any difference between a Mk 5 and Mk 10 even at low pressures.
The Mk 5 and Mk 10 were both regarded as benchmark regulators against which everything else was compared and they both had a reputation for bullet proof reliability. In fact I read a review once where they compared the Mk 10 to the AK-47. Not the best in the world perhaps, but simple, rugged, and utterly reliable even when abused.
The Mk 10's flow rate is significantly less than the 300 SCFM that a Mk 20 or 25 can produce. But to put it in perspective, 100 SCFM is generally regarded as being more than enough for just about any diving situation. So while you can get more performance, it's questionable that you would ever actually need more performance.
The MK 5's flow rate is very slightly less at high tank pressures (around 100-105 SCFM) but falls off to around 65-67 SCFM at low tank pressures. The Mk 5 does however have a large diameter piston head (similar to the Mk 15, 20 and 25) and is very responsive, so I could never tell any difference between a Mk 5 and Mk 10 even at low pressures.
The Mk 5 and Mk 10 were both regarded as benchmark regulators against which everything else was compared and they both had a reputation for bullet proof reliability. In fact I read a review once where they compared the Mk 10 to the AK-47. Not the best in the world perhaps, but simple, rugged, and utterly reliable even when abused.
The Mk 10's flow rate is significantly less than the 300 SCFM that a Mk 20 or 25 can produce. But to put it in perspective, 100 SCFM is generally regarded as being more than enough for just about any diving situation. So while you can get more performance, it's questionable that you would ever actually need more performance.
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Dear DA Aquamaster,
I just read one article about DIR reg setup at http://www.gasdiving.co.uk/pages/misc/kit/regs.htm
We use either Apex Tx50 or the Scubapro G250 - remember to remove the front locking pin on the G250.
What does it mean remove the locking pin? Why?
Thanks,
I just read one article about DIR reg setup at http://www.gasdiving.co.uk/pages/misc/kit/regs.htm
We use either Apex Tx50 or the Scubapro G250 - remember to remove the front locking pin on the G250.
What does it mean remove the locking pin? Why?
Thanks,
The locking pin is a small plastic pin that is inserted through the body into the cover, holding the cover in place. The older G250's didn't have them, but the newer ones do.
Thanks for the info DA, I wouldn't have thought that there was such a big difference. Does anybody know why their is such a difference?
The mk5 is so similar to the mk25 that I thought it would have been closer.
I will have to test my mk5 against the mk20 someday soon.
The mk5 is so similar to the mk25 that I thought it would have been closer.
I will have to test my mk5 against the mk20 someday soon.
With the pistons currently in use in the Mk 15, 20 and Mk 25, (all basically incorporating knife edged seating surfaces) the flow rates are very similar for the Mk 15, 20 and 25.cnctina:
The Mk 15 uses the same basic high pressure bushing idea as the Mk 20 and 25 but in the Mk 15 the bushing on the end is permanently installed. This has of course not prevented the occasional tech from trying to remove it with the resulting need to replace the entrie first stage body. The Mk 15 also uses a C-clip to hold the bushings in place and this requires a modified set of snap ring pliers to remove and install so in general is is more of a pain to work on than the Mk 20 or Mk 25.
But essentially the Mk 15 and Mk 20/25 are nearly identical in terms of operation and performance. They all use concave seat deisgns and pistons with larger stem diameters to greatly improve flow rates compared the Mk 5 or Mk 10. And the replaceable bushings mean tighter tolerances can be maintained which eliminates high pressure o-ring crimping as a problem and in turn allows 300 Bar (4350psi) service pressures in all three regs (as long as they are equipped with DIN fittings.) The repalceable bushings also mean that wear occurring in the hp o-ring groove will not be a problem over time. For the Mk 5 and Mk 10, wear in this area eventually results in increased HP o-ring crimping and leaks that can only be resolved by replacing the first stage body which may not be cost effective.
Popularity is often a function of reputation and the Mk 15 introduced the concave seat design which greatly improved airflow compared to the Mk 5 and Mk 10. But Scubapro unfortunately had problems with the seat material initially used in that design with the result that early Mk 15's had a relatively high rate of seat failures. I believe there may have even been a recall to replace the seats.
So even though the Mk 15 now uses the same seat design and material as the Mk 20/25 and is equally reliable, the Mk 15 is still asscociated by many divers with its initial development and reliability problems which is in some cases complicated by derogatory comments from techs that prefer to work on something else.
The finish was also a different darker colored matte chrome. I think it is equally attractive, but this may be part of the popularity issue. The Mk 15 also did not incorporate the rubber trim boot on the back of the first stage like the Mk 20 and Mk 25 so this area tends to get dinged which chips the chrome and makes it cosmetically less appealing to someone buying one used.
You bring up a good point indirectly. The Mk 5 and Mk 20/25 all use the same diameter piston head which helps responsiveness and IP stability.sailingking:
SP has also went with concave seat designs on the Mk 20 and 25 that improve flow rate significantly. However SP has also since incorporated this same design on current seats for the Mk 5 and Mk 10. So the flow rates for Mk 5's and Mk 10 with the new seats are probably higher than the 20 year old numbers quoted above, although I am not sure by how much. (I would hazard a guess a Mk 10 with a new seat would have flows in the 150 SCFM range.)
The remaining major difference between the Mk 20/25 and Mk 5 is that the piston stem diameter is larger in the Mk 20/25. As all of the air flows though the piston stem, this difference has a big impact on flow rate. Due to area and flow dynamics the increase in diameter also has a non linear impact on flow rate, much like how a 5 inch fire hose will pump more water than two 3 inch fire hoses.
DIY flow rate testing gets complicated by other potentially limiting factors such as variations in supply pressures and limitations in valve design which can limit flow rates more than the first stage being tested. And of course, if you have a reg that will flow 300 SCFM but tank valves that will only flow half that amount, there is little real world advantage to having a first stage with that level of perfromance. So in the real world, there probably is not that much difference between a Mk 5,10, 20 or 25 and they all deliver enough air for nearly any situation.
The mk25 is the current version of the regulator, and is essentialy an upgraded mk20.
The mk 25 has an external intermidiate pressure adjustment, which is nice for service technicians because the first stage no longer has to be taken apart to add or remove shims to change the intermidiate pressure.
There have also been a few changes to the piston for cold water use.
There are also some minor cosmetic changes between the mk20 and mk25.
The mk 25 has an external intermidiate pressure adjustment, which is nice for service technicians because the first stage no longer has to be taken apart to add or remove shims to change the intermidiate pressure.
There have also been a few changes to the piston for cold water use.
There are also some minor cosmetic changes between the mk20 and mk25.
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