Rubber DIN Dust Caps: Leaky Nightmare, or Master Sealer?

[iointerrupt]

Do rubber DIN dust caps leak when rinsing regulators with them? Should they be banished to the landfill, replaced with the one true dust cap, the screw-on cap? Are there more important things I should be working on?

These are the questions that have been plaguing me for the last months. I have seen many (ok, a few) claims, that rubber DIN dust caps, as supplied by regulator manufacturers, are unsuitable for anything but keeping dust out of a first stage regulator. That when left submerged, water will leak past the cap and into the regulator body. And so only by using screw-on caps, which seal against the DIN o-ring, can you safely dunk.

Given these ideas, I set out to find out for the truth. The experimental setup I decided upon is as follows: A 5 gallon bucket with 12" (30cm) of water, two "volunteer" regulators with their factory rubber dust caps on, and then 30 days of waiting:



After a month of staring at the bucket, waiting, not working on more important things, here are the results:

First up, the ScubaPro Mk2:



First we note that there is water in the dust cap! However, the back half of the cap is dry. As for the regulator itself? Not a single drop inside.

Next up, the Poseidon 2960:



Here again, the same result. Water gets into the dust cap around the threads, but not a drop makes it past the DIN o-ring into the regulator body.

So there you have it. Make sure your dust caps are fully seated against the DIN o-ring, and you'll be good to soak for at least 30 days.

Actually, probably want to soak them for less than that, as these regulators came out with a nice layer of slime algae growing on all the rubber parts...

 

[Bigbella]

I've serviced any number of regulators over the years, where the owners either didn't possess your prowess or plain good luck, and experienced all manner of water intrusion from both rubber and screw-on DIN caps, during soaking.

I'd also like to see some subassemblies of those first stages of yours, after thirty days, beyond that of just the connecting stems, since corrosion that I typically saw, especially with the Poseidon 2900 series, didn't really begin there, but made its way down to both the piston and the balanced housing portions.

Scuba manufacturers, as a rule, are a real mercenary lot; and I would bank that Poseidon, for example, would openly advertise it, scream it from the Göteborg rooftops, that their throwaway US 6.00 rubber DIN caps, gotta be the cheapest thing that they produce, could reliably prevent water intrusion to their pricey regs for, what, thirty days?

Instead, they don't -- and clearly instruct end-users to soak their regulators only while pressurized . . .

 

[lowwall]

Knowing humans, I would guess it's more likely that the water was introduced without a dust cap in place and then the cap was put on.

Manufacturer recommendations are based on avoiding liability for customer carelessness rather than actual requirements.

To the OP. Screw on caps avoid accidental movement of the cap while it's being handled in the water. Think of so called "valet" service which probably means 20 regsets being tossed in a trash can full of water, stirred around a few times and left to sit.

 

[happy-diver]

What I have found is when I punch out a thin disc of silicone to stuff in the end of a cap
but I'm only talking screw on caps for oxygen sensors that last years longer risk it or not