Compact First Stage Regulator. good? dry bleed?
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Aas far as I understood from what Tanks explained , the Sherwood need to be constantly pressurized to keep the chamber from being flooded on descent (as the gas compresses and more needs to be injected)
Other designs don’t need that — the ambient chamber is wet (unless it’s an env sealed reg, but tht will have a filler and/transducer) and still don’t need constant pressurization
All you need is a simple open/close so that the HP seat is engaged (and water doesn’t go beyond the tank); most cases that will also close the LP seat so no water will come from the 2nd up the hose
Still Kicking
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CG43
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An O-ring that seals against IP can also withstand a slightly larger gap. Some rework is possible without having to replace the piston right away.
It depends if the regulator has an old style sintered filter built into the piston. If that filter is clogged and no longer works to pass air slowly, the piston would likely have to be replaced as it’s very difficult to impossible to clean the filter back to specs. You might have to look for a working donor piston from another regulator that is out of service for another reason, or find new old stock pistons, which could cost more than the regulator is worth.
Used Gear - Used First Stages - Northeast Scuba Supply Store
northeastscubasupply.com
If yoke is OK and you want a compact diaphragm (my preference), he's got a Mares MR12 and a US Divers Conshelf. They are $70 each and are serviced and O2 clean. If you need DIN, give John a call and see what he can do.
The prices are so low that I think John rebuilds some of these older regs as a hobby/charity. Not sure whether it's for divers who can't afford new or because he just can't stand to see a serviceable old reg get thrown away.
Tanks A Lot
Contributor
I want to clear this up a bit, as Sherwood’s dry-bleed system is unique. Just because it’s old doesn’t mean it’s bad. I’d bet an arm and a leg that other companies would’ve jumped on the idea if Sherwood hadn’t patented it in 1980. It’s superior to the flimsy transducer seals that proliferate the market today in pretty much any metric I can come up with.
Sherwood’s system, by design, can only be used with an open cylinder valve upon descent. It is during the descent that gas needs to be added to the dry chamber. As ambient pressure increases, gas must be added to prevent that pressure from overpowering the check valve. It doesn’t matter whether you’re using Sherwood’s dry-bleed with the Schrader valve or the older style with the sintered filter in the piston, the descent requires an open cylinder valve.
Once you reach your target depth, the newer system with the Schrader valve will function just fine even with the valve closed. The check valve doesn’t bleed air, as ambient pressure equals dry-seal chamber pressure. The older style with the sintered filter is a bit more nuanced. The filter allows gas to pass until intermediate pressure equals ambient pressure. It will slowly equalise those two. This isn’t a major concern, because as long as the pressures are equal, water shouldn’t ingress.
Water should never be able to enter a cylinder if the cylinder pressure is above ambient pressure.
Gas would escape from the cylinder towards the water source, preventing anything from getting inside. Consider what happens during a dive: if a diver runs out of gas, meaning cylinder pressure equals ambient pressure, they (hopefully) begin to ascend. As ambient pressure drops, cylinder pressure becomes higher than ambient pressure again. They may then breathe a little more gas to match ambient pressure, and so on. Crucially, a diver can’t create a “vacuum” inside the cylinder that drops its pressure below ambient. That’s why water ingress into a cylinder is very rare and almost always due to poor compressor performance.
The cases I’ve seen involving water ingress from not compressors sources, were due to user error or stupidity. One case involved empty, assembled but partially open cylinders stored in the bilge of a boat. The open ones ingested copious amounts of saltwater. Another involved “technicians” trying to muffle the loud noise of releasing gas from a cylinder when they did their visual inspections.
Saltwater inside a cylinder destroys the internals orders of magnitude faster than water from a compressor. Saltwater can completely ruin a cylinder in less than a couple of months. Water from a compressor isn’t ideal either, but even years of exposure don’t necessarily result in a condemned cylinder, although they might of course.
No regulator is quite like the Sherwood dry-bleed, but as I said, I bet many wish they were. You should keep any regulator pressurised during a dive. Almost all second stages are downstream by design, which means they seal tighter when you descend without gas. That might sound like a good thing, but it really isn’t. It means that not only the full spring force unopposed by intermediate pressure pushes the seat and orifice together, now ambient pressure is acting over the entire sealing surface of the orifice too. While this won’t destroy your seats immediately, it will cause deeper grooves over time, likely requiring an earlier service than usual.
Some designs perform particularly poorly when submerged unpressurised, such as retractable orifices (Atomic Aquatics) or collapsible inserts in some Poseidons (Jetstream / XStream). These can let water in.
Indeed, the “loss” of gas is negligible, even with constant flow through the orifice and sintered filter. We’re talking about 0.8 to 1.6 litres per hour. That means you’d need to leave it pressurised for around 10 hours to lose just 1 bar on most cylinders. Divers hate bubbles and love to blame even tiny leaks for high gas consumption, which is, of course, nonsense.
Exactly right, descend is the key word here. The flooding would be with regards to the dry-chamber, not necessarily the rest.
That’s a good point! I’ve found cleaning sintered filters to be basically impossible, and I’ve tried a fair bit. The issue is that the particles must be dissolved, you can’t force them out with pressurised air. Salts are often easy enough to dissolve, but sand and grit can also get in, and those are nearly impossible to remove.
In short, Sherwood’s system is ingenious, but it does require an open cylinder valve during descent. Every regulator should be submerged pressurised. While most second stages only suffer a bit of permanent set on the seat, some designs will flood if taken underwater unpressurised.
My suggestion would be to rethink the approach slightly. A pony bottle is most useful when turned on during the dive, and the risk of gas loss is relatively minor. As you correctly noted, the main risk of gas loss is during entry, but even that can be largely mitigated by proper second stage placement.
While I don’t want to assume, I’ve met divers who had Sherwoods with the dry-bleed system on their pony bottles and turned them off during the dive because they were worried about gas loss. Hopefully the 0.8–1.6 L/hour figure makes it clear that this isn’t really a problem. I'm not saying that’s your reason for diving with a closed valve, but it is something I've seen.
What others have said is solid advice too. A Scubapro MK2, or any of its unbalanced piston cousins (Aqualung Calypso, Cressi AC2, Mares 2S), or models from a host of other manufacturers, will serve you well. However, they all expose the main spring to the environment. If you truly want something insulated from water and don’t want to go the Sherwood dry-seal route, you’d need a balanced diaphragm regulator with an environmental seal, or a sealed balanced piston regulator. These are in a different price bracket than simple piston designs and come with their own trade-offs.
In German, there’s a phrase that translates to “egg-laying-wool-milk-sow” and once I find that regulator that does it all without downsides and at a low price, I’ll give you a shout.
Exactly the off chance that I meant, a really “empty” cylinder + a “bad” maneuver (40bar tank + valve drill at 31+m) (that’s just a bad choice regardless)
GODs regulator doesn’t need service, no orings, is always im tune
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It's called a service, there are million people on here to assist you to make these better than any new stuff
And that is if they need a service like my 50 metre Techreational regs that haven't been serviced for years
Have you bought them yet or you going to do that, one step forward three steps back for a while instead
It's a "pony" you're never going to use it, but what you might do is use these as your primary regs instead
Better than a bought one, for people that know their stuff,
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