MK25 S600 breathing hard

[tceylan]

I have a new single tank setup of scubapro mk25 and 2 x S600's. I've been pretty
happy with the performance so far (about 70 dives). Recently I have realized
that my primary second stage was breathing hard and took it to my LDS. They said
first stage was close to being serviced and serviced it for me. The tech said the
second stages were breathing fine and they were well within specs.

However, my second stage is still not breathing like it used to be. The tech told
me that I should not keep the adjustment knob turned down all the way to avoid the reg to develop a groove.. I did not know this and I kept this knob turned down
at max performance at all times (dives+storage).

For my backup reg, the knob is always set to lowest performance.

When I compare the performance of my second stages (with adj. knob adjusted for lowest performance) my primary breathes harder than my backup.

I know I could swap my backup reg with my primary, but having spent
all this money on these expensive gear, I'm expecting to
get top performance from both of the second stages.

I did read the manual for S600's and I don't think there's anything regarding keeping
this adjustment turned up (lowest perf) to avoid a permanent groove, etc.

What do I do now?

 

[Buccaneer]

Bummer! I use the exact same regs and set-up, and I too have the primary dial opened up and the back-up dialed down ( I get free flows using a necklace if I don't) Fortunately, I haven't ran into any probs. What is this "permanent groove" thing all about? I have never heard of it, and can't imagine that you can't adjust the knob to any setting you see fit.

 

[redacted]

I have a new single tank setup of scubapro mk25 and 2 x S600's. I've been pretty
happy with the performance so far (about 70 dives). Recently I have realized
that my primary second stage was breathing hard and took it to my LDS. They said
first stage was close to being serviced and serviced it for me. The tech said the
second stages were breathing fine and they were well within specs.

However, my second stage is still not breathing like it used to be. The tech told
me that I should not keep the adjustment knob turned down all the way to avoid the reg to develop a groove.. I did not know this and I kept this knob turned down
at max performance at all times (dives+storage).

For my backup reg, the knob is always set to lowest performance.

When I compare the performance of my second stages (with adj. knob adjusted for lowest performance) my primary breathes harder than my backup.

I know I could swap my backup reg with my primary, but having spent
all this money on these expensive gear, I'm expecting to
get top performance from both of the second stages.

I did read the manual for S600's and I don't think there's anything regarding keeping
this adjustment turned up (lowest perf) to avoid a permanent groove, etc.

What do I do now?

You use the terms "turned up" and "turned down" and I'm not sure but it sounds like you may be adjusting the knobs opposite of how they need to be adjusted. The S600 should be stored with the adjustment knob all the way out (knob turned counter-clockwise to the stop). With the reg in your mouth, that is turning the top of the knob away from you. This reduces the force on the spring and reduces the tendency of the LP seat to take a set. This is also the EASIEST breathing position. Turning the knob "in", or clockwise, or top of the knob toward you make it harder breathing. Your alternate should be turned in a bit to avoid freeflows when not in your mouth. In most situations, your primary should be adjusted with the knob all the way out.

To soak your reg when not pressurized, the adj knobs should be turned all the way in to the hardest breathing position to prevent water from entering the LP hoses. When store, both 2nds should have the knobs all the way out to avoid LP seat set.

You should be able to easily sense the difference in performance between all the way OUT to the easiest breathing position vs all the way IN to the hardest breathing position. Out has almost a 1/16th inch gap between the knob and the body. IN leaves no gap between the knob and the body.

 

[tceylan]

OK, I remember it wrong. Here's the updated story;

I kept my reg turned down/dialed down (lowest performance) at all times during the dives and storage. Now it's breathing hard even if a turn it on to max performance.

What do I do now if the LP seat took a set as you described?
If it took a set then is the reg hosed up now?

(Why I kept it in lowest performance? I don't know, I guess the performance was enough and
to minimize free flows I just turned it down and kept it like that... )

 

[halocline]

So, if I understand right, you're saying that you have 2 S600s, both connected to the same MK25, and one breathes harder with the inhalation resistance knob all the way out than the other with it all the way in? That makes no sense, especially if a halfway decent tech checked it out and said everything was okay. I would guess AWAP is right and you have the knob adjustment confused.

Just on an outside chance, you're not talking about the venturi knob, which is a little higher up, right?

 

[tceylan]

When testing these regs at surface and also at 20-30 ft;

2 regs both their resistance knob all the way out (best performance). One of them breathes
much easier than the other one.

(The hard breather one is the one which was previously stored with resistance knob all the way in.)

Both has venture knob in 'dive' state (not in pre-dive).

 

[redacted]

OK, I remember it wrong. Here's the updated story;

I kept my reg turned down/dialed down (lowest performance) at all times during the dives and storage. Now it's breathing hard even if a turn it on to max performance.

What do I do now if the LP seat took a set as you described?
If it took a set then is the reg hosed up now?

(Why I kept it in lowest performance? I don't know, I guess the performance was enough and
to minimize free flows I just turned it down and kept it like that... )

Storing it "dialed down" will cause the LP seat to take a set and make you work a little harder to get air flowing. But it really should not be a big difference.

As long as you are still comfortable breathing from it, I would just switch the primary and the alternate until it is time for service and the LP seats will be replaced. You might want to get your tech to do the switch as those hose covers are a bit difficult to pull back and the hose connections will require some special tools. Or you could just switch which one you are using if you don't mind the differenyt hose lengths.

 

[tceylan]

So, the question is with same config one of the regs breathes much better. And in the past, I stored/used the reg in question with resistance knob all the way in (lowest perf), what do I do now?

The reg used to breathe excellent before...

 

[tceylan]

Thanks everybody. So, changing the LP seats should fix this issue. How expensive are the LP seats? (I think parts are covered in my warranty, but I wanted to ask anyway...)

The reg is not that bad at the moment. I dive with it regularly. I just got used to it's excellent
performance.

 

[redacted]

So, the question is with same config one of the regs breathes much better. And in the past, I stored/used the reg in question with resistance knob all the way in (lowest perf), what do I do now?

The reg used to breathe excellent before...

Are you saying that you used to USE your primary with the knob all the way in and it breathed excellent? While I'm sure I could adjust one to perform like that, it would free flow very badly if you opened up that knob.