US Divers SEA First Stage

[Mark Vlahos]

Hi there folks,

I am in a bit of a quandry. I am getting more into technical diving, and have replaced most of my gear. You know, trading up in quality from entry level recreational gear, through better recreational gear, and finally into high quality technical gear. For those of you who have been diving for very long this path is not uncommon. I am at the point where my regulators are showing signs of inadequacy.

I own two US Divers SEA first stages, and they are paired with the non-adjustable version of the US Divers Micra + second stage. I understand that the second stage is not entirely appropriate for technical diving use. Are the SEA first stages also inappropriate? If I replace the second stages with a high quality adjustable model, from one of the major manufacturers am I good to go? The SEA first stages are configured with DIN fittings and the hose length and port size are not an issue for me.

I do not ice dive so the ability to perform in really cold water is not at issue. Most likely the coldest water they regs will see is in the high 40's (F). They could see depths to around 150 feet, using air or more likely NITROX that is appropriate for the depth in question. I would take them into caves as well.

When I go into a shop, I get the standard response that I should replace the regs entirely. I understand this, the shop is in the business of selling gear, and replacing the entire set is easy, and would certainly work. Unfortunately, I am not made of money. Buying two complete regulator sets (for double tanks, or singles with an H valve) is rather expensive.

So I will restate my question, Is the US Divers SEA first stage inappropriate for my use? Remeber, I would be replacing the second stage with a high quality adjustable version from a major manufacturer. I would have the IP adjusted to pair the two correctly.

Many thanks,

Mark Vlahos

 

[DA Aquamaster]

As a primary or backup first stage, the primary issue for technical diving would be flow rate. Ironically the most demanding situation encountered by a first stage in technical diving would probably be deep air diving. Helium mixes tend to flow through regs much better than air or nitrox, so the use of He will extend the useful range of the first stage. I met a cave diver once who used a relatively low performing SP Mk 2's at depths to 300 ft on He mixes and liked how they performed. Your intention to use them to 150 ft on air or nitrox in the 25-26% range is probably about as demanding as it gets for a first stage in technical diving.

I have never seen any stats on flow rates for the SEA first stage but it is basically a Conshelf XIV with a different port arrangement and the Conshelf series has a long history of solid performance even at the depths you are considering. And personally, I don't see a lot of major differences between the Conshelf design and other diaphragm designs currently considered trendy for tech diving.

In my opinion, the flow rate and general performance of any diaphragm first stage pales in comparison to the flow rate and performance of a good balanced piston design, but that is not the same as saying that any diaphragm first stage is not up to the task of technical diving.

Due to their generally small size however, I think the SEA would make a vey good deco reg, assuming you can get them O2 cleaned. So the best solution may well be to upgrade to a higher performance reg when you get to the point of needing to add a 3rd and eventually fourth regulator for deco/stage bottles.