mixing and matching brands

[rescuediver009]

Not to nit-pick, but are you sure the MK25 increases IP at depth more than the increase in ambient pressure? I just read a post that said that "overbalanced" in some cases refers to the design of the piston and seat which prevents the slight drop in IP that even balanced regs experience at really low tank pressures. Just curious here, because I haven't heard of true overbalancing in SP piston regs before.

Yes, it does refer to the prevention of the drop in the IP or it increases the IP to make up for the loss (6 in one hand, half dozen in the other). So, while I am not as familiar with these as I am others, I assume that the overbalancing is an industry standard term that refers to this same effect on Apeks regs which, I am very familiar with. They are all overbalanced.

If you haven't seen the mention of the overbalancing before, take a look.

 

[The Chairman]

You know... I can handle a trickle.

But if you put an upstream secondary reg (like a Poseidon) on any other than a primary that is equipped with either a downstream safe second or safety released valve, then you could have an issue with an IP creep... like the inability to breathe at all.

Frankenregs have been a part of Scuba Diving since we had a second reg manufacturer.

 

[DennisW]

I was told by a UK diver, a while ago, that it was against the law to mix regulators. Why? I haven't a clue. I asked him the same question and he said that he thought there had been an accident where a regulator had failed because the brands had been mixed, so a law was passed to prevent that problem. I seem to remember that there could be some issues with mixing a Poseidon 2nd stage with another brand first stage, although I can't remember exactly why any more. Maybe some of our expert regulator repair people would know. I have one very good course under my belt and I loaned my manual back to the instructor after making some edits. I don't have it back yet, so I can't look up the reference.

However, maybe the guy was blowing smoke. I've never dived in the UK and I do not personally know what their laws say about SCUBA. I was just passing on some heresay.

 

[The Chairman]

Pssst Dennis...

look up just one post! I must have been typing my post when you started to reply!

 

[halocline]

Yes, it does refer to the prevention of the drop in the IP or it increases the IP to make up for the loss (6 in one hand, half dozen in the other). So, while I am not as familiar with these as I am others, I assume that the overbalancing is an industry standard term that refers to this same effect on Apeks regs which, I am very familiar with. They are all overbalanced.

Right, but I think the apeks overbalancing might be different than the SP; I'm really not sure, but what I seem to remember reading is that the apeks overbalancing really does increase the IP above and beyond the increase in ambient to increase flow at greater depth, while the SP simply refers to something in the design of the seat and piston which prevents any IP drop at all at low tank pressure. If this is true, it would have some impact on tuning 2nd stages to the regs, I would think.

Not arguing as I'm hardly qualified, but curious.

 

[Crazyduck]

I have a Poseidon 3965 first stage with a D400 Scubapro 2nd and a Cyklon Octo- No problems here- Batman. And if there was going to be a problem it would be with this combination. If I was buying new- by all one brand and be done, plus servicing is easy. If buying used and putting things together- be creative.

Have fun, Andrew

 

[AquaPix]

Maybe mixing different brand regs is not such a good idea. There are no official tests done with different brand regs and therefore no CE approval. To combine them is actually easy as most regs got the same threads, but this is where the similarities end. There are different intermediate pressures in the first stages of all brands and this alone can make it impossible for you to adjust and fine tune second stages that you screw into the first stage and I don't even want to start with the different flowrates. Also, please ask yourself if you can trust your regs to work in any condition. What can go wrong will go wrong, it is just a matter of time. If you don't get a problem underwater then you will run into a big one the first time when you need to get them serviced. Apparently it is against HSE rules and regulations to sell or service regulators that are assembled with different brand parts (only first and second stages, NOT gauges, LP hoses or transmitters!) and the service centre can be prosecuted.
Let me tell you another story that just happened to me 2 weeks ago in Dahab (Egypt). I went there with a couple of friends to do some trimix diving at the Blue Hole.
When we prepared our equipment a friend of mine assembled Apeks first stages (sorry don't remember which ones) and Scubapro (S600/R390) second stages. His instructor pointed out the problem that could arise from such a combination and told us the HSE story. The instructor should know as he owns one of Londons largest diving schools. But stubborn as my friend is he wouldn't change his reg configuration. End of story? ... he nearly killed himself! At his last dive into the Blue Hole he suddenly got a severe freeflow on his primary reg (S600) at 100m and couldn't shut it down himself. Thank god his instructor reacted quickly and managed to control the situation.
OK, this example is a little bit extreme and some of you might argue now that the average diver will never go to these depths, but do you know which problem can arise from coupling different brand regs and when and where you will run into difficulties.
Please ask yourselves if you want to risk your life (and maybe the one of your buddy!) over such an unneccesary experiment.
By the way "overbalanced" in case of Scubapro first stages means that the intermediate pressure will rise when you reach the last 10 bar in your tank and this could result in a minor freeflow in an unbalanced second stage such as an R190 or R390. Personally I think you should probably be on the surface anyway when your tank gets that low on air ...

Cheers, Andy (AquaPix)
TDI,PSA,CMAS,PADI,DIWA inst.
Scubapro Service Technician

 

[AquaPix]

Hi Guys,

it is actually against HSE regulations to sell or service regs that combine different brand first and second stages (not the gauges!). So, please, please, please, stop recommending it ... it is illegal and could harm or even kill a fellow diver.

cheers, Andy (AquaPix)

 

[The Chairman]

Can you provide us with these "regulations"? I know of no such laws here in the USA.

 

[AquaPix]

Hi Guys,

HSE are english regulations and therefore only apply to England. Stupid or not they are fact here in the UK. But even in the USA i'd be careful to make such a recommendation ... just think of the lawsuit if something goes wrong.

No hard feelings guys, all I am interested is the safety of all our fellow divers.

Cheers, Andy (AquaPix) UK