SP MK 25 IP

[Open Ocean Diver]

Checking the IP of my SP MK-25 because both G250's started to seep air, even with the resistance knobs all the way in. It eventually seemed to lock up around 160 psi on the gauge. Re-adjust 2nds or service the reg? Opinions reg gurus and anyone else with 2 cents to put in? Thanks.

160 is too high. There is another adjustment on the MK 25 where you can bring down the IP, maybe 15 psi, depending on where the adjustment is currently at.

 

[Nemrod]

160 is too high. There is another adjustment on the MK 25 where you can bring down the IP, maybe 15 psi, depending on where the adjustment is currently at.

The Mark 25 has externally adjustable IP. Adjust IP with air off and depressurized. The 160 psi IP is out of spec. I would first adjust the IP to specification. If it continues to creep upward then it is time for service. The Mark 25 does have a somewhat mushy lock up but 20 psi of creep from initial lockup is not acceptable.

The IP should be 125 to 145 psi @3,000 psi and 300 psi. The IP is a 5/32 Hex and it is under the plastic cap. Again, per the SM the regulator is not to be under pressure during adjustment as this can damage the seat and piston knife edge.

 

[halocline]

well that's not THAT bad (still needs service prob), mine 2 minutes from 115 to 130, takes 5 minutes to 140, an hour to 150.. bad creep

Not that bad? 20 PSI of creep, likely only stopped by the 2nd stage leaking…..that’s not anything I would dive with.

The OP’s regulator needs to be rebuilt. I keep my SP balanced piston regs on the low side, usually around 127-130 PSI, with zero creep.

 

[Mobulai]

Not that bad? 20 PSI of creep, likely only stopped by the 2nd stage leaking…..that’s not anything I would dive with.

The OP’s regulator needs to be rebuilt. I keep my SP balanced piston regs on the low side, usually around 127-130 PSI, with zero creep.

Oh forgive me I misworded it- I meant to say the “profile” mushiness of lockup in comparison to what I’m experiencing (115 to 150 from instantaneous to 2 hours) isn’t as bad, but still bad
We both need rebuilds for sure

 

[halocline]

Oh forgive me I misworded it- I meant to say the “profile” mushiness of lockup in comparison to what I’m experiencing (115 to 150 from instantaneous to 2 hours) isn’t as bad, but still bad
We both need rebuilds for sure

Forgive me for oversimplifying. That amount of creep, or anything more than a few PSI, is unacceptable in my opinion. When I rebuild or even just check a first stage, I’ll leave it pressurized for an hour or longer, and if there is any appreciable creep, that stage gets a new seat. If it creeps with a new seat, then it gets a new piston or I resurface the piston edge. (that procedure has been carefully and thoroughly described by rsingler)

I’ve worked on lots of the SP balanced piston regs, and excepting MK10+ or the middle generation MK20 brass tip piston, I have never had any problems getting rid of IP creep.

Virtually all of my diving for the last several years has been in caves, with two tanks and sometimes a stage. This means I need regulators to hold steady pressure without being breathed on every few seconds. But even for single tank, recreational diving there’s no excuse for tolerating IP creep. It’s easy to fix.

 

[Johnsonsa93]

Checking the IP of my SP MK-25 because both G250's started to seep air, even with the resistance knobs all the way in. It eventually seemed to lock up around 160 psi on the gauge

It's not that the IP has locked up it's that the amount of air leaking from the 2nd stage(s) at 160 PSI is equal to the increase in IP from the creep that is happening. Remove both second stages and put plugs in those LP ports and check the IP again, I bet it continues it's creep above 160. (please don't do this unless your IP gauge has a OP valve on it as if the IP were to creep too high you could blow the LPI hose.)

The Mark 25 has externally adjustable IP. Adjust IP with air off and depressurized. The 160 psi IP is out of spec. I would first adjust the IP to specification. If it continues to creep upward then it is time for service. The Mark 25 does have a somewhat mushy lock up but 20 psi of creep from initial lockup is not acceptable.

The IP should be 125 to 145 psi @3,000 psi and 300 psi. The IP is a 5/32 Hex and it is under the plastic cap. Again, per the SM the regulator is not to be under pressure during adjustment as this can damage the seat and piston knife edge.

This is the correct advice right here. But it sound like your piston tip & seat have been worn too far for this issue to be fixed from using the 1st stage adjustment screw.

As everyone else has mentioned in the thread it's time to service your reg. At least your seat needs to be replaced. From my experience though both MK25 pistons and Atomic Piston can get a lot of micro scratches over time and can still have a decent amount of creep after servicing and changing out the seat, what a lot of people refer to as a "Mushy IP" after service.

A tip I picked up from the people at Atomic is to polish the piston with Dremel 421 compound. A little bit on the tip of the piston polished with a paper towel can help a bit. I put some on the piston tip & some on a Q-tip which I use fitted in a drill to get a nice polish on pistons. Don't think this will take out major dings or scratches in the piston but it can give a heavily used piston a bit more life. I've attached a before and after picture of an atomic piston I've done this to recently to give you an idea.

 

[NitroxSam]

Thanks for that advice. I'm going to definitely have it serviced. I guess if the piston was really bad it could just be replaced along with the HP Seat?

 

[davehicks]

Thanks for that advice. I'm going to definitely have it serviced. I guess if the piston was really bad it could just be replaced along with the HP Seat?

At extra cost. The piston is not a part of the service kit and might need to be ordered.

 

[Johnsonsa93]

At extra cost. The piston is not a part of the service kit and might need to be ordered.

I think NitroxSam mentioned that his reg was a MK25. if he is in the parts for life program the tech can get the piston replaced at no charge if the creep is enough that the technician servicing it deems it an issue.

I just checked the repair guide and ScubaPro has no allowable creep listed. If you go off Atomic's suggestion I believe it's 8 PSI, which used to be 5 PSI but I'm guessing they were seeing a lot of people have issues keeping the creep under 5 PSI.

 

[NitroxSam]

It's a old reg thst I purchased used, so I guess the costs will be on me.