MK10 - to grease or not to grease, that is the question.

I've just picked up two nice used MK10s which you can see here. Click on the photos to enlarge. These are my first piston regs. The one with the black rubber seal around the ambient chamber is an MK10 rebuilt with the 'plus' components.

The other reg is a standard MK10, looking like it was just driven off the showroom floor — it's a beauty!

Neither have any silicone grease in the ambient chambers.

I dive warm, tropical water. I'm pretty fastidious with my stuff - they'll get soaked in fresh water at the end of the dive day.

I presume the standard protocol for my type of diving is to 'not' put silicon grease in the ambient chamber - yes? no? (My service guy automatically left it out of the MK10+).

In the case of using silicone grease in the ambient chamber, I think that rubber ring with holes is designed to keep some of the grease from oozing out (?). If you use grease, are you supposed to twist the rubber ring so it's holes don't line up with the holes in the ambient chamber? (I would think that pressure would still be able to get through to the interior of the ambient chamber).

I would not grease it at all. I would use a little christo lube and thats it. You can not trun the black band it has a bump on it that lines up to stay in place. If you have it serviced you can get the new thermo sleeve for the piston. just my to cents.

I dive an MK10, but an older model with the metal yoke nut and no indented groove around the barrel (I bought it new a couple of years ago--someone had had it in storage). What exactly is the purpose of the indented barrel groove? I also have a brand new (still in the original box) MK10+, which looks like your MK10s as it has the indented barrel groove.

beachnik:

I've just picked up two nice used MK10s which you can see here. Click on the photos to enlarge. These are my first piston regs. The one with the black rubber seal around the ambient chamber is an MK10 rebuilt with the 'plus' components.

The other reg is a standard MK10, looking like it was just driven off the showroom floor — it's a beauty!

Neither have any silicone grease in the ambient chambers.

I dive warm, tropical water. I'm pretty fastidious with my stuff - they'll get soaked in fresh water at the end of the dive day.

I presume the standard protocol for my type of diving is to 'not' put silicon grease in the ambient chamber - yes? no? (My service guy automatically left it out of the MK10+).

In the case of using silicone grease in the ambient chamber, I think that rubber ring with holes is designed to keep some of the grease from oozing out (?). If you use grease, are you supposed to twist the rubber ring so it's holes don't line up with the holes in the ambient chamber? (I would think that pressure would still be able to get through to the interior of the ambient chamber).

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Mk 10 versus Mk 5

A Mk 10 with a metal trim piece below the yoke is almost certainly a Mk 5 as the body diameters are different and the Mk 5's metal yoke trim piece des not fit the Mk 10. On the other hand the later Mk 15, Mk 20 and Mk 25 ribbed plastic trim piece would probably fit on a Mk 5.

On the Mk 5, the part of the reglator that supports the LP port swivel is longer and the line separating it from the body of the first stage (the part with the yoke in it) will be just under the trim piece. On the Mk 10, this dividing line is just forward of the yoke trim piece and the ambient pressure holes are in the main body, not the swivel cap.

Trim boot

The early Mk 10's just had small holes in the ambient chamber to retain silicone. This worked ok but was not great as over time the silicone woudl leka and ooze out to the point where it would need to be repacked. If you dove a lot, it woudl need to be topped off mid season.

Consequently the boot and a groove to hold it were added to retain the silicone. The boots I have now all have a tab on them that fits in the hole that is otherwise partially covered by the trim piece under the yoke. This prevents the boot from rotating and keeps the holes in the boot aligned with the holes in the ambient chamber. This works well if no silicone is used and the larger holes on this later version make it easier to rinse the ambient chamber. If the chamber is filled with environmental suilicone, the tab would need to be cut off the inside of the ring so that the ring can be rotated to cover the ambient pressure holes.

When SP first got into nitrox compatibility, they went with Christolube and stopped using environmental silicone due to concerns of cross contamination. (This was back when everyone O2 cleaned regs for anythiong over 23% O2. The cross contamination concern is still a valid issue as silicone on the tools or bench coudl contaminate a reg you do want truly O2 clean.) At that time SP techs had a habit of removing the black SPEC boots and throwing them away - leaving a rather unsightly groove for the ring exposed. I do not recall if the original boots had holes in them or if they were solid and/or if they had a tab to prevent rotation. Given that these boots were thrown away I suspect they were either solid or tabless and thrown away to preven the holes from being rotated by the user to block the now empty ambient chamber which would would make rinsing the ambient chamber difficult once it flooded.

If I had one of the later SPEC booted Mk 10's and were using it in warm water, I'd leave it silicone free with the holes exposed as the reg is easier to rinse with the larger holes. With an early Mk 10 without the boot, I'd be tempted to fill it with silicone or Christolube as they are much harder to rinse after a dive due to the very small holes.

In cold water, the SPEC booted Mk 10 with either silicone or Christolube would be the way to go.

That said, it will be very rare to find a SP tech that will be willing to pack an ambient chamber with anything since SP has not done it that way in over 10 years and it is no longer an SP approved technique. A silicone packed chamber is very messy to service as all the old silicone needs to be cleaned out at annual service, so SP policy aside, it annoys amny techs. And the cross contamination issue is still a valid concern and the tech would need to O2 clean all his or her tools and work surfaces again.

Filling the chamber wiuth christolube (the slightly less expensive MCG111 veresion) would be an option but woudl cost about $15-$20 for the Christolube. Apollo used this approach for environmental sealing on their regulators while SP developed the TIS system for their newer models. The old SP SPEC system and the christolube version adapted by Apollo frankly works better though, especially compared to a reg like the Mk 10 that was designed to use a silicone filled ambient chamber that now has virtually no environmental protection.

SP does have a piston bushing to cover most of the piston head, but it is not a full TIS system, it does not cover the piston stem and it does not fit all of the Mk 10 pistons that are out there.

Thank you, DA...another 'tour de force' of an explanation! My MK10 is an early MK10 (not an MK5; the all-metal yoke nut I mentioned is not the trim piece at the bottom of the yoke--that's plastic--but rather the key on top that screws into the yoke and locks it to the tank). I now dive my MK10 (use only air) in warmer waters (upper 60s at the moment)--with no silicone/Christolube packed into it--so I take it the main issue with the smaller ambient chamber holes for me is rinsing--the unit will not rinse as well due to the tiny holes (if I read you right, packing the chamber with silicone even when diving warmer water will protect the inner parts and compensate for the poor rinsing). (I might note that before moving to Hong Kong, I dove this same MK10 in the cold winter waters of northern New England--as low as 40 degrees F and routinely down to 100'+--with no silicone packed into the chamber--never had a problem.)

Hum...now I'm not quite so keen on my MK10--I had thought it the perfect workhorse for my diving (spearfishing, actually) situation here: warmer, mirky, often silty, waters, rarely deeper than 70 feet, and I rinse the reg in a barrel of fresh water on the boat and store the reg on the boat. I'd rather not use and leave on the boat any of my stash of more showcase regs (a new MK10+, two mint MK20s, a mint MK20UL, a new MK18UL, and an MK25). Maybe I should just go with my MK7 honker, which is serviced and ready to dive--how would this hunk of metal hold up with weekly use, quick rinses, and damp storage on a boat? I dive a single AL80, so the heavy honker would help with trim. I use an Air II, so only two LP hoses, which works nicely with the MK7 (I can remove the swivel adapter).

Thanks again!

mahjong:

Thank you, DA...another 'tour de force' of an explanation! My MK10 is an early MK10 (not an MK5; the all-metal yoke nut I mentioned is not the trim piece at the bottom of the yoke--that's plastic--but rather the key on top that screws into the yoke and locks it to the tank).

Maybe I should just go with my MK7 honker, which is serviced and ready to dive--how would this hunk of metal hold up with weekly use, quick rinses, and damp storage on a boat? I dive a single AL80, so the heavy honker would help with trim. I use an Air II, so only two LP hoses, which works nicely with the MK7 (I can remove the swivel adapter).

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The yoke screw (all metal) or yoke screw assembly (metal screw w/ plastic knob).

My Mk7 only has 2 clusters of ambient holes so it takes some extra rinsing and soaking to clean that out. If you damage the seating surface in the ambient chamber, there is no cap to replace. The whole thing becomes a paper weight.

Thanks AWAP...so "yoke screw" is the proper nomenclature...

Okay, so I'll leave the MK 7 on the shelf...perhaps just stick with my MK10 and leave it in the barrel soaking a bit longer...actually, I think as long as I use it weekly I'm okay...

awap:

The yoke screw (all metal) or yoke screw assembly (metal screw w/ plastic knob).

My Mk7 only has 2 clusters of ambient holes so it takes some extra rinsing and soaking to clean that out. If you damage the seating surface in the ambient chamber, there is no cap to replace. The whole thing becomes a paper weight.

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mahjong:

Thanks AWAP...so "yoke screw" is the proper nomenclature...

Okay, so I'll leave the MK 7 on the shelf...perhaps just stick with my MK10 and leave it in the barrel soaking a bit longer...actually, I think as long as I use it weekly I'm okay...

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Another option would be to carefully drill out at least one of the little spec holes on thr Mk10 to the full diameter. Then use a squirt bottle of FW to rinse the ambient chamber a couple times before the soak to get he other nooks and cranies.

Thanks again, AWAP...that certainly sounds sensible...but my relationship to my Scubapro regs is not entirely sensible...honestly I cannot imagine taking a drill to my reg...but perhaps I can work on altering my mindset and viewing this sort of structural modification as strengthening the bond between me and my reg...I'll be thinking about it...

awap:

Another option would be to carefully drill out at least one of the little spec holes on thr Mk10 to the full diameter. Then use a squirt bottle of FW to rinse the ambient chamber a couple times before the soak to get he other nooks and cranies.

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Ah, my favorite first stage... I have a million of them and am always looking for a few more. Never had a problem with these babies. I don't grease em.