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**newhaul** · 03-08-2017, 08:27

Quote:

Originally Posted by a64pilot

You could not with a regular Scuba reg, but it could be done, for example my CPAP is set to 8 in of water which is I think about .3 PSI, and I can't over breathe it. I have tried out of curiosity.
We are talking only very shallow depths of course, or otherwise it would have to have a way to ramp up pressure with increasing depth

Look at how big the hose is on a cpap my daughters unit has a 1inch hose that is about 4 ft long now restrict that to 3/8 hose and 50 ft long bet you could over breath it then.
Takes pressure to move volume thru small hose.

transmitterdan · 03-08-2017, 09:55

Denverdon,

Care to share your calculations on the flow rate and pressure drop of 0.25" hose?

You will find that physics requires higher pressure than you are estimating. It takes pressure to work the regulator. Without several psi pressure drop the regulator will not regulate.

denverd0n · 03-08-2017, 11:15

Quote:

Originally Posted by transmitterdan

Care to share your calculations on the flow rate and pressure drop of 0.25" hose?

The number I quoted came from the website of an air hose manufacturer, the hose being specifically rated for breathing.

Quote:

Originally Posted by transmitterdan

It takes pressure to work the regulator. Without several psi pressure drop the regulator will not regulate.

Yes, of course. Which is why I have repeatedly mentioned that as an issue that could complicate things. Of course, "several psi" is one thing, and thinking that it needs a differential of 60-80 psi is a whole different thing.

Nonetheless, I suspect that the main reason most diving regulators need as much pressure in the hose as they do is just because that's the way it is done with tanks. And hookah regulators have always been made by simple spring modifications to existing SCUBA second-stage regulators.

We know that regulators can be made to work with only 40 psi in the hose. They already exist. My suspicion is that they could be made to work with significantly less pressure than that. Perhaps someday I will get around to trying it.

I'm certainly not going to believe that it is impossible just because, "that's how it has always been done."

transmitterdan · 03-08-2017, 16:29

And yet if it was a safe thing to do surely it would be marketed by reputable companies. As you point out the math ain't that hard to cypher. But once you add up all the required pressure drops needed to supply breathing air safely through a long small hose I think you will find that the well established and relative safe systems are not over designed that much. At least not enough to make a big dent in the required pump power.

Pauls · 03-08-2017, 17:58

For all those asking questions about flow capacity, pressure drop, etc there are on line calculators that make simple work of this. From Gates (the hose and belt company) 50' of 1/4" ID hose with a supply pressure of 25 PSIG will flow 3CFM at a pressure drop of 5.38 PSI, ie delivered pressure at 3 CFM = 19.62 PSIG.

**a64pilot** · 03-08-2017, 18:22

It could be done, and it would be safe, however you would need a big cumbersome hose, and what would be the advantage of a low PSI system? Lower power consumption would be the only possible advantage I can think of, but I'd bet that the number of customers that care how much power their Hooka draws is slim to none.
So far as cleaning a boat hull anyone with much experience at all can handle a Hooka suddenly failing.

denverd0n · 04-08-2017, 05:35

Quote:

Originally Posted by a64pilot

...and what would be the advantage of a low PSI system?

Probably none at all. Like I said before, this is just a mental exercise.

denverd0n · 04-08-2017, 05:37

Quote:

Originally Posted by Pauls

For all those asking questions about flow capacity, pressure drop, etc there are on line calculators that make simple work of this. From Gates...

You don't have a link to where you found this, do you? I poked around the gates.com website some and could not find it.

EDIT: Okay, never mind. I found it here... http://tinyurl.com/y9gdb7kj

**a64pilot** · 04-08-2017, 05:43

Quote:

Originally Posted by denverd0n

Probably none at all. Like I said before, this is just a mental exercise.

I like to participate in those myself, sometimes it educational

snokid · 04-08-2017, 06:54

Quote:

Originally Posted by funjohnson

*we were given a Sea breath hookah unit from the companies' owner. We haven't even had the chance to try it yet. I'm only posting as I thought something from their FAQ would be germane to this discussion about operating PSI:

What pressure does the system operate?

Sea Breathe incorporates a unique variable pressure system that allows the air pressure to increase as the diver descends. Thus if you are at shallow depths, i.e. cleaning your boat hull, the pressure (and hence the current draw from the battery will be minimized., approximately 12-14 psi. When the diver descends to say 20 feet the pressure will automatically adjust to about 20 psi. This feature ensures that there is the minimal drain on the battery during the dive, which of course increases battery duration.

Matt

Matt I love your videos....

But

I have a system from them and it does not increase in pressure or I should say the one I have doesn't....

Mine is a twin pump unit, plug one inlet for 1 diver or use both pumps for 2 divers... supposed to save power not having one compressor pumping air but it's still spinning just not getting inlet air...

As far as a review it's a good unit. Does the job for sure.

The downsides are
price
the inflation bag they use as a regulator.

Really I like my DIY system better and that's what I use the most.

I have read the posts about the puma being a consumer pump from china. All I can say about that is the one I bought wasn't soaked in oil and I wasn't breathing oil. I guess if someone was worried about that it wouldn't take too much to rinse the tank out.

Watching your videos I can see you have the skills to put together your own kit no problems.

Bob

Matt Johnson · 04-08-2017, 10:17

Thanks Snokid for watching the videos.

What were the issues you found with the inflation bag reservoir tank? It seemed like a smart alternative to a rigid tank, but I could see a leak being an issue.

Matt

fstbttms · 04-08-2017, 10:23

Quote:

Originally Posted by denverd0n

Have you ever tried using a regulator that will operate at 30 or 40 psi?

I strongly suspect that, with the right regulator, and the right compressor, you would find that half that much pressure could provide all the air you would ever need.

No. No reason to.

snokid · 04-08-2017, 13:44

Quote:

Originally Posted by funjohnson

Thanks Snokid for watching the videos.

What were the issues you found with the inflation bag reservoir tank? It seemed like a smart alternative to a rigid tank, but I could see a leak being an issue.

Matt

The main thing I don't like is the bags.

They are large both while using them and also storing them. Made of the same material as a dinghy, so you roll up the hose then you have to store the bags but they are attached to the hoses.

The compressor on the unit I have is in a heavy duty plastic box. If you have the box in a dinghy and are diving I have come up to having the lid shut. easy enough fix with a bit of rope.

But take my other setup, the puma and breathing hose. Toss the battery compressor and hose into the dinghy drive out flip a switch start diving.

The only thing I have not tried with my DIY version is 2 divers at once at depth more than 6' I know it works fine in shallow water like cleaning your hull, but diving reefs not sure if the puma has enough volume/pressure for 2 divers, been 30' single I know it works fine.

Bob