Twin tanks

[WD8CDH]

Good point. Some are small and some are large.

 

[wedivebc]

Hey, what about connecting the two first stages with an hp hose between their respective hp ports???

If it works ??? it could save the extra SPG and keep the air supply balanced between the two tanks, and also be less costly than a manifold.

Just asking!!!:idea:

As well it would add multiple failure points and what problem is it trying to solve?

 

[Belmont]

As well it would add multiple failure points and what problem is it trying to solve?

Not to solve any problem. Just to offer a less expensive option compared to a manifold.

A quicker simpler way to join two tanks. No valve replacement and no tank draining, just install a set of bands and you are good to go.

Now for the addition of multiple failure points, I say there are fewer. The structure of a manifold is way more complicated than a single hose, more O rings, more parts.

Just a way for the OP to try twin tanks with a safer less complicated setup than separate units. Simpler gas management, one less SPG

 

[mikerault]

You would not get enough flow. Have you tried this or know of anyone who has done this successfully?

Mike

 

[ArcticDiver]

I was going to switch to double but mostly for more air not for technical diving so do I realy need to manifold my tanks.

After glancing over the responses to your question I see the usual personal philosophy driven replies. Oh well, this IS the internet.

You asked if you "need" to manifold your tanks. No you don't. In fact for the person who isn't able for one reason or another to develop and maintain manifolded doubles shutdown skills it is probably safer to use independent doubles.

Some folks said to "use a pony". Nonsense. A pony is merely a second tank that is smaller than your primary tank. You are right on track in deciding to be redundant with two identical tanks.

Some have said to "just get a bigger single tank". Again. If you want more gas and redundancy there is no substitute for double tanks. With a set of twinning brackets you can have independent doubles with the extra gas and redundancy almost anywhere you go.

Well, it is up to you. It is your money and your dives. Oh, what do I use? I use both single, independent doubles and manifolded doubles. It all depends on what I'm doing. For example: When I travel I want redundancy and manifolded doubles are seldom available so I take my brackets with me and twin up two tanks at the destination.

 

[WD8CDH]

Not to solve any problem. Just to offer a less expensive option compared to a manifold.

A quicker simpler way to join two tanks. No valve replacement and no tank draining, just install a set of bands and you are good to go.

Now for the addition of multiple failure points, I say there are fewer. The structure of a manifold is way more complicated than a single hose, more O rings, more parts.

Just a way for the OP to try twin tanks with a safer less complicated setup than separate units. Simpler gas management, one less SPG

The crossover in a manifold is slightly more complicated than a hose and it's fittings but the crossover has more rugged and reliable parts so it would be safer. But, if the passages in the HP ports and in the hose fittings are large enough, the hose will work.












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[halocline]

Using a HP hose to connect two regs in place of using a manifold to connect two tanks is not such a great idea. It's not that the hose presents "multiple failure points" but think about a couple of scenarios. First, you need a hose with 2 identical ends; that's not a standard HP hose, so custom hose. Second, assume one reg starts freeflowing. If you shut off that post, you will save the gas in that tank but that reg will still flow because it has a source of HP air from the other reg. (and the other tank) But, since the flow through the HP hose is restricted, it's not like you could breathe off the reg on the shut off tank, it would just slowly drain the opposite tank. This is true for either reg.

The isolator manifold allows you to shut off the flow to either reg and still have the gas in both tanks. The "hose connection" as you are proposing does the opposite; it allows gas from either tank to go to both regs at once whether you want it to or not. So you're sort of disabling the shut off valves for the individual tanks. You can shut off a tank, but then you have no access to that gas and you still have not solved the problem of the leaking reg.

As far as flow between the tanks, I suppose it would equalize after each breath; you'd be drawing from the tank attached to the reg you're breathing, then the restricted HP flow between the tanks would quickly equalize.

One other thing, if a manifold (or tank, or burst disc) springs a leak you can isolate and save the gas in one of the tanks. If the HP connecting hose springs a leak, you're going to lose both tanks. Or, in an appropriate usage, you're hosed.

I think I'm right about this, but if not, someone can cheerfully correct me. I've never tried it, just thinking through how it would work.

 

[Belmont]

You would not get enough flow. Have you tried this or know of anyone who has done this successfully?

Mike

I don't know, I haven't.

But you have to consider that the demand by the diver is intermittent and the flow trough the hose is constant. All that is needed it to keep the pressure equal in both tanks.

Has anyone here on the board tried it?

 

[wedivebc]

Just a way for the OP to try twin tanks with a safer less complicated setup than separate units. Simpler gas management, one less SPG

Why do you say it is safer than independent tanks?
Read Mattboys post above

 

[Belmont]

Using a HP hose to connect two regs in place of using a manifold to connect two tanks is not such a great idea. It's not that the hose presents "multiple failure points" but think about a couple of scenarios. First, you need a hose with 2 identical ends; that's not a standard HP hose, so custom hose. Second, assume one reg starts freeflowing. If you shut off that post, you will save the gas in that tank but that reg will still flow because it has a source of HP air from the other reg. (and the other tank) But, since the flow through the HP hose is restricted, it's not like you could breathe off the reg on the shut off tank, it would just slowly drain the opposite tank. This is true for either reg.

The isolator manifold allows you to shut off the flow to either reg and still have the gas in both tanks. The "hose connection" as you are proposing does the opposite; it allows gas from either tank to go to both regs at once whether you want it to or not. So you're sort of disabling the shut off valves for the individual tanks. You can shut off a tank, but then you have no access to that gas and you still have not solved the problem of the leaking reg.

As far as flow between the tanks, I suppose it would equalize after each breath; you'd be drawing from the tank attached to the reg you're breathing, then the restricted HP flow between the tanks would quickly equalize.

One other thing, if a manifold (or tank, or burst disc) springs a leak you can isolate and save the gas in one of the tanks. If the HP connecting hose springs a leak, you're going to lose both tanks. Or, in an appropriate usage, you're hosed.

I think I'm right about this, but if not, someone can cheerfully correct me. I've never tried it, just thinking through how it would work.

Good point, you are right.

The hose "manifold" was just an idea I offered to the OP who was not sure if he should spring for a complete twin setup.

It definitely has drawbacks compared to an isolated manifold and thus it is not as safe.

We can think that if one primary gets a free flow the hose will still feed it but at a rate that will give the diver enough air to safely thumb the dive.

As far as being less complicated than separate tanks: it's taking into consideration the lack of experience of a single tank diver in managing two air supplies and maintaining the necessary equilibrium between them, reading two SPG's and alternating between regulators.