Mixing and matching

[vertigolady]

I've never been able to find a straight answer on this. What's the deal with mixing and matching regulators and octos from different manufacturers/of different qualities? If you have a balanced regulator, do you need to find a balanced octo? If unbalanced, do you need to find an unbalanced partner? What about environmental sealing? It's often hard to find this information about octos and I never know...

And I assume if the qualities match, mixing different brands doesn't matter as long as they fit together, yes?

Thanks...

 

[DiveGear4Less]

Manufacturers will have you believe you must use the same brands together because they want you to buy their regs. However, it really doesn't matter. While putting a high quality and low quality reg set together will have an overall effect on the performance of the high quality reg, they will still work together. That being said, don't skimp out on the octo. There are octos out there that breathe horribly. The low profile models come to mind. They tend to breathe wet and hard and are hardly the type of reg you would want to use when you really need an alternate air source.

 

[rcs9250]

It is true. Some regulator first and seconds should not be matched with out some thought first. Some second stages are upstream and would require an over pressure valve (OPV)to be used safely. Some Seconds require higher than typical intermediate pressures as well. Poseidon seconds are the usual suspects for the above features.
Good regulators but different than main stream regs.

 

[herman]

With few exceptions (Poseidon) most any modern first stage can be used with any second stage. Upstream second stages are uncommon today. None of the major regulator manufacturers are currently making upstream valved second stages and few if any have been made since the early 60s. (Poseidon may be the exception- I do not have any experience with them). Even then, an OPV is not required if either of the second stages are a downstream design. 99% of all current regs use an IP (pressure in the hose between the first and second stages) in the 135 to 145 psi range and any second stage can be tuned to work well within that IP range. Pretty much any time a second stage is connected to a different first stage it needs tuning anyway so that is not an issue.
Balancing is a non issue. It is likely the most misunderstood feature on a dive reg. It's purpose is to maintain a constant work of breathing over the entire range of tank pressures, basically the reg breaths the same from 3000 to 300 psi. In an unbalanced first stage the IP will vary by some amount over the range of tank pressure which will intern cause an unbalanced second stage to breath differently as tank pressure changes. The vast majority of divers will not notice the difference in a modern unbalanced reg. From an operation perspective it does not matter which stage, first or second, is balanced and there is no reason to balance both the first and second stage. Balancing either the first or second stage will accomplish the same result, balancing both stages is redundant. It does no harm but it also does no good. Balancing either the first or both second stages will keep the second stage breathing evenly over the entire range of tank pressures and will increase the overall performance of the reg. Bottom line is you can balance the first stage or the second or both but doing both adds complexity to the overall reg with little benefit. Plus, there are 10s of thousands of divers happily diving day in and day out with neither stage balanced.

The biggest reason to keep the brands of regs the same is for service. Many shops will not service several brands so you may have issues getting service but otherwise there is no reason not to mix and match as you like.....most of my regs have 2 or 3 brands of first/second stages installed at any given time. Since I do my own service different brands are not an issue.

 

[rcs9250]

With few exceptions (Poseidon) most any modern first stage can be used with any second stage. Upstream second stages are uncommon today. None of the major regulator manufacturers are currently making upstream valved second stages and few if any have been made since the early 60s. (Poseidon may be the exception- I do not have any experience with them). Even then, an OPV is not required if either of the second stages are a downstream design. 99% of all current regs use an IP (pressure in the hose between the first and second stages) in the 135 to 145 psi range and any second stage can be tuned to work well within that IP range. Pretty much any time a second stage is connected to a different first stage it needs tuning anyway so that is not an issue.
Balancing is a non issue. It is likely the most misunderstood feature on a dive reg. It's purpose is to maintain a constant work of breathing over the entire range of tank pressures, basically the reg breaths the same from 3000 to 300 psi. In an unbalanced first stage the IP will vary by some amount over the range of tank pressure which will intern cause an unbalanced second stage to breath differently as tank pressure changes. The vast majority of divers will not notice the difference in a modern unbalanced reg. From an operation perspective it does not matter which stage, first or second, is balanced and there is no reason to balance both the first and second stage. Balancing either the first or second stage will accomplish the same result, balancing both stages is redundant. It does no harm but it also does no good. Balancing either the first or both second stages will keep the second stage breathing evenly over the entire range of tank pressures and will increase the overall performance of the reg. Bottom line is you can balance the first stage or the second or both but doing both adds complexity to the overall reg with little benefit. Plus, there are 10s of thousands of divers happily diving day in and day out with neither stage balanced.

The biggest reason to keep the brands of regs the same is for service. Many shops will not service several brands so you may have issues getting service but otherwise there is no reason not to mix and match as you like.....most of my regs have 2 or 3 brands of installed at any given time. Since I do my own service different brands are not an issue.

You are now to the dive shops in Raleigh what Osama Bin Laden is to the U.S. military. Watch your back.

 

[herman]

You are now to the dive shops in Raleigh what Osama Bin Laden is to the U.S. military. Watch your back.

I am well know in the LDSs in Raleigh. One of the great things about Raleigh is the dive shops are honest with their customers and work together for the good of the diving community.

 

[MauiScubaSteve]

As an Instructor I actually prefer to have a low profile hard and wet to breath alternate, because then my students all get to experience what most likely they will run into in the real tourist rental insta-buddy world.

As a guide I actually prefer to have a low profile hard and wet to breath alternate, because if those lame KIA vacation divers don't follow the briefing to look at their SPG regularly, tell me when they get to half a tank and when they get to 1000 psi, they deserve a hard and wet to breath alternate.

 

[LeadTurn_SD]

Hi Herman (not sure if you are still following this thread),

What are your thoughts on mix n' matching an over-balanced first with an unbalanced 2nd?

All of my firsts are "normal" balanced 1sts, not "over-balanced", and I'm not sure that I'll own an over-balanced first in the near future.... but I've been curious if there is actually a potential for slight freeflows at depth (if the unbalanced 2nd was tuned too aggressively).

My thought is that if the over-balanced 1st is actually raising the IP more than the increase in water pressure as depth increases, that the potential exists for an increasing IP at the 2nd stage valve... which in an unbalanced 2nd could overpower the resistance of the demand valve spring and result in freeflow.... Or am I just confused about what is happening with an over-balanced 1st ? (Smart money is that I am confused ).

Thanks.

Best wishes.

 

[herman]

Hi Herman (not sure if you are still following this thread),

What are your thoughts on mix n' matching an over-balanced first with an unbalanced 2nd?

All of my firsts are "normal" balanced 1sts, not "over-balanced", and I'm not sure that I'll own an over-balanced first in the near future.... but I've been curious if there is actually a potential for slight freeflows at depth (if the unbalanced 2nd was tuned too aggressively).

My thought is that if the over-balanced 1st is actually raising the IP more than the increase in water pressure as depth increases, that the potential exists for an increasing IP at the 2nd stage valve... which in an unbalanced 2nd could overpower the resistance of the demand valve spring and result in freeflow.... Or am I just confused about what is happening with an over-balanced 1st ? (Smart money is that I am confused ).

Thanks.

Best wishes.

Good question.
To start with, "overbalanced" is an incorrect term IMO. When discussing first stages, balancing is the regulating of the IP to compensate for varying tank pressure as opposed to depth compensating, which is what we are actually talking about. Interestingly, balancing works to keep the IP constant while depth compensation actively varies the IP according to depth. IMO a more proper term would be "over depth compensated" but I guess it does not sound as cool to the marketing folks. In any case, if a first stage is designed to increase the IP in excess of the amount needed to compensate for ambient pressure increases at depth (i.e. "overbalancing") then you are correct, an unbalanced second stage may start to free flow after a certain depth. If, when and by how much would be determined by a lot of factors including how much the IP is increased over the amount needed to compensate for ambient pressure changes. So far, I have not found any information on just how much these regs are "overbalanced". You could easily tune an unbalanced second to not free flow at depth but at the expense of shallow performance. Primary second stages sold with “OB” first stages balanced so you would not see a problem with them and most octos are tuned on the heavy side anyway, esp the unbalanced ones, so odds are you will not see a problem with them unless the tech is tuning them more like a primary second stage. To set up an unbalanced second stage for use with a reg that is “overbalanced” you would really need a value for the increased IP over ambient at depth and then tune accordingly. My guess is the overbalancing is not that much otherwise the manufs would be setting themselves up for a lot of complaints about freeflowing octos at depth. A balanced second stage would be necessary for both the primary and octo second stages if you want to tune both for max performance when attached to a “overbalanced“ first stage..

You have got me curious as to how much excess IP is required to make an octo set at say 1.5” wc start to free flow……dang another project.

 

[scubafanatic]

Hi Herman (not sure if you are still following this thread),

What are your thoughts on mix n' matching an over-balanced first with an unbalanced 2nd?

All of my firsts are "normal" balanced 1sts, not "over-balanced", and I'm not sure that I'll own an over-balanced first in the near future.... but I've been curious if there is actually a potential for slight freeflows at depth (if the unbalanced 2nd was tuned too aggressively).

My thought is that if the over-balanced 1st is actually raising the IP more than the increase in water pressure as depth increases, that the potential exists for an increasing IP at the 2nd stage valve... which in an unbalanced 2nd could overpower the resistance of the demand valve spring and result in freeflow.... Or am I just confused about what is happening with an over-balanced 1st ? (Smart money is that I am confused ).

Thanks.

Best wishes.

...from what I've been told from dive shops whose opinions/expertise I trust, you are correct, mixing an unbalanced octo with an overbalanced 1st-stage is a 'no-no' for just the reason you describe.