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A Moderate from 04/01/07-24/12/12
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I am led to believe that the scubapro mk25 is a good dir reg i.e. ;routing but what about the mk20 also what is a good price for the mk25 second hand .All help is appreciated
Pete
Hopefully NickB will be along cos he is chapter and verse on this.....

The MK20 is essentially a MK25 without the ability to alter the IP from the outside. There was also something about the design which meant you can cause damage if you are a hamfisted service agent....plus a different material used for the piston I think.

My stage regs are MK20 and AFAIAC offer a very economical alternative to the MK25....they are often cheap on eBAY.

It is possible to buy the parts to convert a MK20 into a MK25.

HTH
Mal
 

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The MK20 is essentially a MK25 without the ability to alter the IP from the outside.
Spot on. The Mk25 evolved from the Mk20 with the addition of an IP adjustment (sort of). Really, you don't get much adjustment; plus/minus one bar is about it. Major adjustment is still done by adding or removing shims inside the reg, but once it's set (in the factory), it doesn't shift by much.

It continues to evolve: the ambient pressure holes have gradually elongated, the piston is now a composite plastic affair, rather than brass and it also has a much sharper HP end and an anti-freeze teflon coating. The ambient pressure chamber is now ribbed, not for extra pleasure, but for improved anti-freeze characteristics (hence the Mk25AF name).

It is possible to buy the parts to convert a MK20 into a MK25.
Correct, but buying a Mk20 and all the parts you'd need to convert it to the latest Mk25 spec would cost more than buying a Mk25 to start with. The new piston is a very worthwhile upgrade and your service technician should swap it out for free during a service. I service my own and my LDS will swap an old brass piston for a new one for free.

I use Mk25AFs for my backgas and Mk20s for my deco regs.

I may try to gather together some images of the various generations of Mk20/25s to aid identification.

Watch this space.....
 
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