My "new" independent doubles setup

[Open Ocean Diver]

The MK 5 is a balanced 1st stage the IP stays the same regardless of tank pressure above the IP.
The IP is changed by adding or subtracting main spring shims not by tank pressure. The IP needs to be similar on both MK5s as it is on mine 135 psi on both MK5. The IP hasn't changed since I last serviced them in 2017. They are over due but that's one of the beauty things about MK5's they are very forgiving of neglect to point.

My experience no more than 5 psi from 300-3000 tank pressure.

 

[Kupu]

The MK 5 is a balanced 1st stage the IP stays the same regardless of tank pressure above the IP.
The IP is changed by adding or subtracting main spring shims not by tank pressure. The IP needs to be similar on both MK5s as it is on mine 135 psi on both MK5. The IP hasn't changed since I last serviced them in 2017. They are over due but that's one of the beauty things about MK5's they are viry forgiving of neglect to point.

Thanks for the reply and a very entertaining thread. I enjoy diving AIR1s as well.

I DIY service and use MK5s and MK10s, it is my understanding and experience that IP on piston first stages does drop a bit with tank pressure, despite being balanced. Generally a drop in the range of 5-10 PSI from full tank to empty although that number varies depending on which regulator is being looked at. You have checked the IP on your MK5s and see 135 PSI on both full and empty tanks?

 

[AfterDark]

Thanks for the reply and a very entertaining thread. I enjoy diving AIR1s as well.

I DIY service and use MK5s and MK10s, it is my understanding and experience that IP on piston first stages does drop a bit with tank pressure, despite being balanced. Generally a drop in the range of 5-10 PSI from full tank to empty although that number varies depending on which regulator is being looked at. You have checked the IP on your MK5s and see 135 PSI on both full and empty tanks?

@300 psi as recommended. yes

 

[Kupu]

@300 psi as recommended. yes

What about IP with full tank? If you have 135 IP with 300 psi tank, I would expect to see something in the range of 140-145 at 3000 psi.

 

[Open Ocean Diver]

Here’s my test with and without the switch. Tank 1000 psi, MK2 plus.

Without:

:

 

[AfterDark]

What about IP with full tank? If you have 135 IP with 300 psi tank, I would expect to see something in the range of 140-145 at 3000 psi.

Same @3000 135 psi

 

[Open Ocean Diver]

Delete

 

[Open Ocean Diver]

With switch…2-3 SCFM difference.

 

[Kupu]

Same @3000 135 psi

Very nice, that beats the IP performance of every SP piston first stage I have owned.

 

[James79]

Without switch…2-3 SCFM difference.

View attachment 675646

If I'm reading that right, no inline shutoff is showing 17 SCFM, and with shows 15 SCFM.
If I'm an airhog and using 1 CFM RMI, I can assume that I'm only inhaling half of the cycle, and call it 2 CFM flow on inhale at surface. So I would have to be at 7.5 ATM or greater than 200 ft to reach the with switch CFM limit.
That, and nice PJs!

Respectfully,

James