Scubapro Mk11 lack of environmental sealing?

[SaltyWombat]

I thought all diaphragm regulators were environmentally sealed, but then learned of the Scubapro Mk11. How can it be unsealed? I thought the point of diaphragm regs was the seal.

So is the Mk11 unsealed in the way the Mk25 is?

 

[davehicks]

All diaphragm regs are partially sealed, some are fully "environmentally" sealed. The Mk25 is a piston reg and not sealed.

In a diaphragm 1st stage the moving parts are all sealed under the diaphragm with just an opening for ambient water pressure to push on the outside of the diaphragm. Environmental sealling adds a second external diaphragm and pressure transmitter that applies ambient pressure to the main diaphragm.

In an unsealed piston 1st stage the moving piston and spring are exposed to water.

 

[lowwall]

Go read these two posts from me and @tbone1004 to understand the difference between standard diaphragm first stages like the MK11 and environmentally sealed diaphragm first stages like the MK17. As a bonus you'll see how that compares to piston regs:
- Piston or diaphragm 1st stage ? - post 10
- Piston or diaphragm 1st stage ? - post 11

I'll include the pertinent illustrations below if you have any other questions:

Standard diaphragm first:

Above with environmental seal drawn in on the right side of the reg. The hand drawn purple diaphragm transmits the ambient pressure to the spring. Note that there should be no water in the main spring section between the two diaphragms (although a few older types of environmentally sealed first stages require that this space be filled with a liquid with a low freezing point, typically oil or alcohol).

 

[SaltyWombat]

So basically:

• Sand in the Mk25 (piston reg) ambient chamber can cause damage since an o-ring is exposed there
• Sand in a Mk11 (non-environmentally sealed) ambient chamber won't cause problems
• Sand can't even enter a Mk17's environmentally sealed ambient chamber

 

[BoundForElsewhere]

I love my MK11T. Thank you, Lex.

 

[ScubaBadger32]

So basically:

• Sand in the Mk25 (piston reg) ambient chamber can cause damage since an o-ring is exposed there
• Sand in a Mk11 (non-environmentally sealed) ambient chamber won't cause problems
• Sand can't even enter a Mk17's environmentally sealed ambient chamber

mk 19 too right? same with mk17

 

[rhwestfall]

mk 19 too right? same with mk17

The MK-17 and MK-19 are "basically the same" in regard to being: (1) a diaphragm regulator and (2) a dry environmentally sealed ambient chamber.

 

[John Trecker]

Looking for a new reg for rec diving only. Looking at getting MK series. Is there a strong reason to choose one over others due to these points and worth additional money?

 

[rhwestfall]

IMHO - Sealed (17/19) is more tolerant to sub-par rinsing.. Also the better choice for true cold water....

 

[Jake 10]

Go read these two posts from me and @tbone1004 to understand the difference between standard diaphragm first stages like the MK11 and environmentally sealed diaphragm first stages like the MK17. As a bonus you'll see how that compares to piston regs:
- Piston or diaphragm 1st stage ? - post 10
- Piston or diaphragm 1st stage ? - post 11

I'll include the pertinent illustrations below if you have any other questions:

Standard diaphragm first:

Above with environmental seal drawn in on the right side of the reg. The hand drawn purple diaphragm transmits the ambient pressure to the spring. Note that there should be no water in the main spring section between the two diaphragms (although a few older types of environmentally sealed first stages require that this space be filled with a liquid with a low freezing point, typically oil or alcohol).

Excellent information