SP MK 25 IP

[halocline]

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

This is a MK25, correct? A new piston will be $70 or so at a dive shop, unless the price has gone up. If this was my reg, I would start by replacing the seat and inspecting the piston edge with a magnifying glass. If there are any small scratches, just polish them out with a mild abrasive. I use a product called micromesh, it’s basically a set of abrasive cloth that starts at 1200 grit and goes to 10,000. It was developed for polishing visible scratches out of acrylic, so it’s very safe for use on steel.

If you’re not doing this work yourself, you need a competent tech. That’s not always easy to find, unfortunately. The training for regulator technicians by the big manufacturers is laughable. You could contact rsingler on this forum; he’s a very good technician and will absolutely get rid of your IP creep.

The SP dealer official policy on this would be to replace the piston. Why…because it’s idiot-proof and they make money on it. In reality, I have never once seen a MK25 piston that couldn’t be polished to work perfectly. However…..there is a different issue with the MK25 piston. Unlike all earlier versions of SP balanced pistons, the MK25 ‘composite’ piston has an internal o-ring seal between the steel shaft and the plastic head. If/when that tiny o-ring fails, the policy is to replace that piston. I have known someone who has carefully disassembled a composite piston and replaced that o-ring, but it’s not a supported procedure.

This thread is getting longer and if you’re not the person with the MK25 that creeps to 160PSI, sorry and you can ignore my reply! But it may be useful information for someone else. IP creep in any decent quality 1st stage is unacceptable and easy to fix. First stages have one job to do; deliver a steady, reliable IP to the 2nd stage. When working correctly, they do that very well.

 

[Johnsonsa93]

This is a MK25, correct? A new piston will be $70 or so at a dive shop, unless the price has gone up. If this was my reg, I would start by replacing the seat and inspecting the piston edge with a magnifying glass. If there are any small scratches, just polish them out with a mild abrasive. I use a product called micromesh, it’s basically a set of abrasive cloth that starts at 1200 grit and goes to 10,000. It was developed for polishing visible scratches out of acrylic, so it’s very safe for use on steel.

If you’re not doing this work yourself, you need a competent tech. That’s not always easy to find, unfortunately. The training for regulator technicians by the big manufacturers is laughable. You could contact rsingler on this forum; he’s a very good technician and will absolutely get rid of your IP creep.

I just checked my shops POS and we have the full piston assembly listed at $90 (I believe you can buy just the piston which will cut $10 or $20 off the price) . If a customer requested me to resurface the piston with MicroMesh I would charge shop time which is in 10 minute ($20) and 30 minute ($36) increments. anything over 40 minutes and it is almost more cost effective to replace the piston especially knowing about the o-ring at the bottom of that piston.

If you're doing it yourself and you don't mind the additional labor time then I can see resurfacing the piston being worth it.

Either way thanks for the useful info, @halocline

 

[NitroxSam]

This is a MK25, correct? A new piston will be $70 or so at a dive shop, unless the price has gone up. If this was my reg, I would start by replacing the seat and inspecting the piston edge with a magnifying glass. If there are any small scratches, just polish them out with a mild abrasive. I use a product called micromesh, it’s basically a set of abrasive cloth that starts at 1200 grit and goes to 10,000. It was developed for polishing visible scratches out of acrylic, so it’s very safe for use on steel.

If you’re not doing this work yourself, you need a competent tech. That’s not always easy to find, unfortunately. The training for regulator technicians by the big manufacturers is laughable. You could contact rsingler on this forum; he’s a very good technician and will absolutely get rid of your IP creep.

The SP dealer official policy on this would be to replace the piston. Why…because it’s idiot-proof and they make money on it. In reality, I have never once seen a MK25 piston that couldn’t be polished to work perfectly. However…..there is a different issue with the MK25 piston. Unlike all earlier versions of SP balanced pistons, the MK25 ‘composite’ piston has an internal o-ring seal between the steel shaft and the plastic head. If/when that tiny o-ring fails, the policy is to replace that piston. I have known someone who has carefully disassembled a composite piston and replaced that o-ring, but it’s not a supported procedure.

This thread is getting longer and if you’re not the person with the MK25 that creeps to 160PSI, sorry and you can ignore my reply! But it may be useful information for someone else. IP creep in any decent quality 1st stage is unacceptable and easy to fix. First stages have one job to do; deliver a steady, reliable IP to the 2nd stage. When working correctly, they do that very well.

I won't be working on it myself, so I'm kind of at the mercy of my LDS. We'll see what they say when they open it up and get eyes on. Hopefully it's just just the seat and the piston is OK. I didn't know pistons were so pricey! Thanks for the info.

 

[Nemrod]

If this is taken as derrogatory towards dive shop service, so be it, but I doubt the shop monkey would know how to polish the knife edge with rouge or Micro Mesh. Most likely this regulator if it is continuing to creep upward will need a new seat and maybe a knife edge polish. But if that is the case they will just give you back a creepy regulator with a new seat and a still slightly scratched piston knife edge or replace the piston and charge you another $90. Call me skeptical, thus the reason I do my own work. But sometimes we are pleasantly surprised, it happens now and then.

 

[NitroxSam]

So far my local has been good. This might just be the true test however.

 

[Johnsonsa93]

but I doubt the shop monkey would know how to polish the knife edge with rouge or Micro Mesh

Sadly this is usually the case. Its more of a symptom from the fact that training / the certification process from manufactures is lackluster at best and that LDS generally cant afford / don't need a full time service tech. LDS's generally have someone who does it here and there along with several other jobs at the shop. The same way you're going to get a lower level of training if you took a sidemount class from someone that only dives and teaches sidemount once a year Vs an instructor primarily dives sidemount and teaches the class 100 times a year.

If possible try to find shops who have a dedicated service tech. As the saying goes, jack of all trades master of none.

 

[buddhasummer]

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

It is that bad.

 

[Mobulai]

It is that bad.

What do I call mine then, Satan? (Also it now whines and squeals and leaks air as well from the ambient chamber — so probably yea)
I defo need to see how them bushings look like, my first mk20/5 to open actually, should be a fun rebuild

 

[Johnsonsa93]

What do I call mine then, Satan? (Also it now whines and squeals and leaks air as well from the ambient chamber — so probably yea)
I defo need to see how them bushings look like, my first mk20/5 to open actually, should be a fun rebuild

The whine / squeal can be fixed by 1) cutting the bushings 2) rotate the seat 90 degrees and 3) flipping the springs. Those tips are from a SP technical bulletin

the leak from the ambient chamber could possibly be from damage to the metal of the 1st stage body where the piston head o-ring seals against the body. Also possible if the piston shaft o-ring is damaged it could be from there. If the sealing surface for the piston head o-ring is damaged you'll need to replace the cap ( p/n: 107.13.012) that connects between the body and the swivel turret.

It's worth mentioning that if you have an IP creep AND an ambient chamber leak (if it's from the piston head o-ring) then your creep is worse than you think it is. Strong chance the piston will need to be replaced if this is the case.

 

[Mobulai]

I hit the motherlode!

It's worth mentioning that if you have an IP creep AND an ambient chamber leak (if it's from the piston head o-ring) then your creep is worse than you think it is. Strong chance the piston will need to be replaced if this is the case.

Didn’t think of all these together like that, thanks for making me aware.
so it is in a curiously bad state lockup wise.

I was suspecting already the piston oring for the leak, got maybe pinched by previous owner/service tech by ramming the piston through.
I just thought my (later discovered whine/2nd test) whine is that oring flapping and „supersonicaly farting“ and leaking to the ambient chamber
The creep is at the edge for sure, common dinom is piston, so probably I have to payout for a new piston if either shaft or blunt edge are scored :/

I hope I don’t need a new cap, I’ll have to hunt for a cheap(er) mk20 to scavenge for that — no shop is gonna sell me that I suspect :laughs frantically with looming anxiety about project paperweight: