In order to keep your rebreather functioning at its best, it's important to keep up with routine maintenance and care. By properly maintaining your rebreather, you will reduce future repair costs, optimize your rebreather's performance and extend its life. While this is not an all-encompassing list of items and most unit specific rebreather manuals or dive training materials explain the basic requirements to clean and maintain your rebreather, here are some regular maintenance needs to keep in mind.
It is much easier to do a basic clean up after each day of diving versus letting sorb dust and moisture build up, mix and dry over several days. After a day of diving (even if you're diving the next day), open up the head and wipe it down; remove any moisture from the cell cartridge and leave it out to dry. Also, wipe down moisture buildup in the canister and clear out any sorb dust if present. After the canister is wiped out and dry, use the CCR canister lid to seal the scrubber in between days of diving and leave the head open to air out.
Keep it dust-free
We mentioned earlier, it's much easier to be proactive versus reactive when it comes to keeping your rebreather clean. Keeping your rebreather free of sorb dust is extremely important! When moisture and sorb dust mix, it sticks to everything inside of your rebreather and dries like cement.
Built up sorb can create O-ring leaks and become more difficult to remove in time. It's much easier to wipe down the head and canister after a day of diving, removing any dust and moisture versus removing built up sorb.
If you find yourself in this position, take a damp paper towel and chip away at the buildup to remove it and keep it clean in the future. If there are areas in the head you cannot access with a paper towel, damp Q-tips work well too.
O-ring care and maintenance
Keeping your O-rings clean and lightly lubricated will make connecting, disconnecting, and sealing items on your rebreather much easier, as well as reduce wear on the O-rings. To keep your O-rings clean and lubed, first remove the O-ring by simply pinching and gently pulling it out of its groove versus using picks to pry it out. Doing so will reduce the chances of damaging your O-rings.
Once the O-ring is removed, use a damp towel to remove any build up sorb dust or debris. Once the O-ring is clean and smooth, place a small amount of lubricant (SubGravity recommends Tribolube 71) on the tip of your index finger then rub the lube between the tip of your finger and your thumb. Remember, a little goes a long way here. Next, you'll simply slide your index and thumb over the entire O-ring to lightly lube it up. Remove any excess lube and inspect for damage and debris before re-installing.
Your rebreather loop and counterlungs are an extension of your body. Specifically, they are an extension of your respiratory system. Studies have shown that loops and counterlungs can build up bacteria leading to lung infections, if they are not kept clean and disinfected after use. This alone should be enough motivation to keep them clean!
If you're doing multiple dives in a day, you can reduce the amount of moisture build up (drool, or commonly referred to a "bio lube" and "lung butter") in the loop by opening them up and clearing it out between dives. If you opt to do this, make sure to, at minimum, do a positive and negative check before doing your general predive check since opening up the loop compromises the seal on the rebreather.
After each day of diving, rinse out your breathing hoses, counterlungs and mouth piece with water and Steramine. If you aren't sure what Steramine is, click here. To use Steramine, all you have to do is mix a single tablet with a gallon of water and once dissolved, flush through your loops and counterlungs. There is no need to rinse out the loops and lungs with freshwater, Steramine kills bacteria upon drying (not while flushing). If you happen to flush Steramine through your bailout valve or DSV (dive surface valve), make sure to rinse the mushroom valves out with fresh water since Steramine has been known to warp and shrink mushroom valves.
While a little off topic from disinfecting, something to think about is if your rebreather is left over night to dry out in an area exposed to bugs, you may consider bunching up paper towels and stuffing them in the opening of your loops and lungs to ensure a bug doesn't move in… While that would make for an exciting pre-breathe, I am sure we can all agree we would rather avoid such situation.
Track the life of your cells
There are definite rules to replacing oxygen sensors. Most manufacturers recommend replacing cells after 12 months of use or 15 months after the date of manufacture, whichever comes first. These guidelines work well; however, it is a common misconception that if the rebreathers electronics pass calibration and the cell is within the "use by" dates, it should be good to go. You need to check for cell linearity regularly as well as track the millivolt (mV) output of each sensor. Over time, you will see the cells begin to degrade slightly. However, you can usually catch a cell that is going bad when it first begins to show a rapid decrease in mV output. If one day a cell read 11 mV in air and 52 mV in oxygen, and the following day it reads 9 mV in air and 40 mV in oxygen, this would be an indication of that cell coming to the end of its usable life. Because we can see the cell beginning to degrade rapidly, it is likely to be current limited at higher PO2s and should be replaced before use even though it is still within the acceptable output range.
Solenoid Care and Replacement
While fairly uncommon, solenoid failures can quickly ruin your dive and pose a potentially lethal scenario. Even though your solenoid typically isn't a user serviceable component, there are still a few things you can do to help avoid a catastrophic solenoid failure on your dive.
Take care of your oxygen first stage. This is the most likely site for moisture and contaminants to enter the solenoid causing corrosion and damage. Always replace the DIN first stage cap anytime the regulator is not connected to a cylinder and ensure the cylinder valve is dry and clean before connecting the first stage.
Inspect for damage. While it is difficult to see what type of condition the inside of your solenoid is in, you may be able to get a good idea by removing and inspecting the hoses from your oxygen first stage. If you see any signs of corrosion or debris in the low-pressure ports of the first stage or the hoses themselves, there is a good chance that the inside of your solenoid looks the same.
Talk to the manufacturer about replacing the solenoid if uncertain. In the grand scheme of things, oxygen injection solenoids are relatively inexpensive. If you are suspicious of its condition, just go ahead and have the factory or service center replace it. You could save yourself a lot of stress, potentially save a dive, and most importantly, reduce risk of a failure in the water.
While this isn't an all-encompassing list of items needed to maintain and care for your rebreather, these can certainly help! Following a regular maintenance and care routine is an important step to keep your rebreather functioning properly for years to come. Doing so will reduce the chance of missing dives due to equipment failures and increase your overall experience while diving your rebreather. Follow your unit-specific rebreather manual for detailed information about the care and maintenance of your unit and consult the manufacturer to see when your rebreather should be serviced.