Best Reg at 100ft?

[jwlast]

I'm currently diving a Sherwood Oasis. Love the reg down to approx 70ish ft. About 100ft or so I feel the performance starts to drop off, breathing becomes a bit tougher with the Oasis.

Question is, based on experience, what reg gives the best performance in the 100-120ft range? All my diving is warm water (Hawaii). I know there are a few variables to consider here, but what reg would folks recommend that doesn't suffer a performance drop off below 100ft?

Thanks.....

 

[DA Aquamaster]

jwlast once bubbled...
I'm currently diving a Sherwood Oasis. Love the reg down to approx 70ish ft. About 100ft or so I feel the performance starts to drop off, breathing becomes a bit tougher with the Oasis.

Question is, based on experience, what reg gives the best performance in the 100-120ft range? All my diving is warm water (Hawaii). I know there are a few variables to consider here, but what reg would folks recommend that doesn't suffer a performance drop off below 100ft?

Thanks.....

I have used Scubapro Mk 10's, Mk 15's and MK 20 and 25's down to 150 ft on a regular basis with no problems. Any of these first stages deliver more than enough air. I have used Balanced Adjustable, G250 and D400 second stages at depth and all are more than adequate.

 

[liormic]

My sets are also Scubapro.
I would sujest you go for the MK2. An old one but works great at those depth even when shering the octopus with your buddy, it still delivers a good amount of breathing gas for the both of you.
I have an old version of it (15 years old) and still works great. Never fails.
There's also SEPA wich I didn't use yet but a very reliable friend of mine has tham and according to him, they're also great.

enjoy.

 

[scywin]

I used to dive the Oasis and then bought a ScubaPro reg when it was time for an upgrade. I found it more comfortable, but I also replaced my first stage at the same time. The advice I was given is if you are only going to replace one, do the first stage. Otherwise you won't get the full performance from the second stage no matter what model it is.

You might find if you replace your first stage the Oasis is fine.

 

[keyshunter]

which Oasis do you have? I have an old Blizzard circa 1991,(basically the same as an Oasis) which had literally hundreds of dives on it in the early 90's at least a dozen beyond 150' and it breathed fine. All I did was have the IP increased when I moved to a warm water area. We still use this old reg quite frequently. It is going to the Caymans as a backup next month.

I have a newer Oasis, about 1999 which is just miserable at anything approaching 100'. It has been worked on by a tech at least 5 times and is better, but not very good. We use it as an absolute --everything else down--last ditch reg. This unit has driven me to USD ( sold and serviced by the same shop). I thought I had just gotten a bad one, but maybe not.

 

[jwlast]

You raise an interesting point about replacing the first stage. With the Oasis (2003 model) I'm using a Genesis GS2000 first stage. Originally had the GS2000 second stage, hated its performance in the 100ft range, assumed it was the second stage, and made the swap to the Oasis. Still not getting good perforamce in the 100ft range. Might be time for a complete change (first and second stage).

Anybody using the CRESSI-SUB Air Plus?

 

[DeepTechScuba]

I am not familiar with Sherwoods other than that they have a good reputation. You need to ask your Sherwood dealer if your reg is "balanced" or "unbalanced."

I dive with a ScubaPro Mark 20 first stage and 2 ScubaPro S600 second stages attached to it. This is a balanced reg.

I also have a ScubaPro Mark 2 first stage which I will match up with a ScubaPro S600 second stage for a pony or stage bottle. The Mark 2 reg is NOT balanced.

A balanced reg should perform well all the way down to 150 ft.

An unbalanced reg with start to show breathing resistance anywhere deeper than 50 ft.

If you are going to start diving deep, defined as more than 50 ft, then you need a balanced reg.

 

[scubafool]

jwlast once bubbled...
You raise an interesting point about replacing the first stage. With the Oasis (2003 model) I'm using a Genesis GS2000 first stage. Originally had the GS2000 second stage, hated its performance in the 100ft range, assumed it was the second stage, and made the swap to the Oasis. Still not getting good perforamce in the 100ft range. Might be time for a complete change (first and second stage).

Anybody using the CRESSI-SUB Air Plus?

jwlast, I'm curious if you ever noticed reduced flow with your GS2000 when you rolled over on your back? If so, did you notice a change when you changed your second stage? I ask because I also have a GS2000, and that is my biggest gripe about it . I guess breathing patterns vary, but I've had mine to 130' with no complaints. It doesn't supply 2 people very well @ 60" though.

 

[jwlast]

When you talk balanced, are you talking the first stage, the second stage or both?

 

[DA Aquamaster]

The flow rate of the first stage at depth is the controlling factor in most cases. Most decent quality second stages will perform well at depth, but a pointed out above, the worlds best second stage will not perform well if the first stage cannot supply it with enough air at the full intermediate pressure. Boosting the IP can also boost the airflow of the first stage, so you may want to have your IP checked and possibly adjusted before decidig to upgrade.

I have used the Scubapro Mk 3 and early production Mk 2 and both are fine regs with bullet proof reliability, but can be out breathed when working hard at depth. The Mk 2 Plus has a little higher air flow, but it still would not be my first choice for a deep diving reg. Many tech divers use them on stage bottles, but then He mixes flow through them much easier than air.

A balanced first stage will have a more stable intermediate pressure than an unbalanced first stage. In an unbalanced first stage the high pressure air from the tank presses directly on the HP seat in the first stage and provides some assitance in opening the seat. As tank pressure decreases, so does the amount of assist, and the intermediate pressure consequently falls slightly as tank pressure decreases. With a standard non adjustable downstream second stage, this means the cracking effort will increase slightly as tank pressure falls. In the early days of diving this was useful for "feeling" when your air supply was getting low.

A unbalanced second stage is similar to an unbalanced first stage in that the LP air feeding the second stage presses directly on the seat and provides an assist in opening the seat. If intermediate pressure falls, like it will in an unbalanced first stage, the breathing effort increases slightly.

A balanced second stage uses a balance chamber on the other side of the poppet holding the seat to ensure the force on the seat remains equal regardless of IP. However, this is really not completely balanced as for saftey it must still maintain a downstream design where an overpressure in the LP hose (from a frozen first stage for example) will force the seat open before the max pressure tolerated by the LP hose is exceeeded.

High performance regs tend to also have balanced first stages and in many cases balanced second stages, but balancing in and of itself does not make a reg high performance.