Very Low Pressure SCUBA Tank

[KISS]

I know nothing about SCUBA, so bear with me, this may be a stupid question.

Is there some reason you couldn't use a manual pump to fill a tank to say 10 atmospheres (about the pressure inside a bike tire, so should be doable) and use that for brief, shallow dives (like cleaning the hull)? A standard 0.39 ft3 tank at 10 atmospheres should have enough air for about 10 minutes by my estimation.

[Shrew]

Now, I'm admittedly not a diver. however, a quick google search and a little public school education tells me:

Atmosphere = "atm"
lb per square inch = "psi"

1 atm = 14.6959 psi.

14.6959 x 10 = 140.6959

10 atm = 140.6959 psi.

That is WAY over any bicycle or automobile tire pressure rating.

[KISS]

Originally Posted by Shrew

Now, I'm admittedly not a diver. however, a quick google search and a little public school education tells me:

Atmosphere = "atm"
lb per square inch = "psi"

1 atm = 14.6959 psi.

14.6959 x 10 = 140.6959

10 atm = 140.6959 psi.

That is WAY over any bicycle or automobile tire pressure rating.

If you google "bike tire pressure," the first result says that road tires have a typical PSI of 80-130.

[Davidhoy]

Originally Posted by KISS

I know nothing about SCUBA, so bear with me, this may be a stupid question.

Is there some reason you couldn't use a manual pump to fill a tank to say 10 atmospheres (about the pressure inside a bike tire, so should be doable) and use that for brief, shallow dives (like cleaning the hull)? A standard 0.39 ft3 tank at 10 atmospheres should have enough air for about 10 minutes by my estimation.

You'll be lucky to get anywhere close to 145 psi (10 bar) with a bike pump. The problem is that scuba first stage regulators take tank pressure and reduce it to 140 psi intermediate pressure to send to the second stage regulator. Without sufficient pressure in the tank, the first stage won't crack open, and you'll be sucking dry almost right away.

-David

[KISS]

Originally Posted by Davidhoy

You'll be lucky to get anywhere close to 145 psi (10 bar) with a bike pump. The problem is that scuba first stage regulators take tank pressure and reduce it to 140 psi intermediate pressure to send to the second stage regulator. Without sufficient pressure in the tank, the first stage won't crack open, and you'll be sucking dry almost right away.

-David

Got it. Is there an electric pump that would be safe to use to fill a tank (still not to normal pressure, but to something well over 140 so as to make the tank usable)? Or would you say a hookah is the better option? ...the huge cost of a proper SCUBA compressor can't be justified for the limited purpose I have in mind.

[Lepke]

I'm a former diver. A Hookah is your cheapest bet. A compressor that produces over 150psi is expensive and expensive to run. When a dive tank gets down to 500psi you should be near the end of your dive. I use a hookah for changing zincs, etc., and it works fine. Fast to setup and use and no trip to get tanks filled.
Don't gather dive equipment and dive without dive school. It's easy to kill yourself, I nearly did as a teen.

[Davidhoy]

Originally Posted by KISS

Got it. Is there an electric pump that would be safe to use to fill a tank (still not to normal pressure, but to something well over 140 so as to make the tank usable)? Or would you say a hookah is the better option? ...the huge cost of a proper SCUBA compressor can't be justified for the limited purpose I have in mind.

As someone else has already pointed out, a hookah system is your best bet. Just make sure that the air intake is nowhere near the engine or generator exhaust.

[sailjumanji]

A couple of the bottom cleaning guys in my marina use simple compressors in the dock, with hose to regulator. My sister who is certified says this is dangerous as they could be breathing in line oil droplets from the compressor. Comments? At least two divers here are using the cheap "pancake" compressors.

[Kenomac]

They're probably oilless with an inline filter. You can by a decent 110v model at the home depot for $99.

[Shrew]

Originally Posted by KISS

If you google "bike tire pressure," the first result says that road tires have a typical PSI of 80-130.

My Mtn bike tires run around 30psi. My dirtbike tires run around 13psi. Maybe some performance road bikes get up to 80-130psi. You'll find most recreational bikes out there are riding around with significantly less.

[Jdege]

Originally Posted by Shrew

My Mtn bike tires run around 30psi. My dirtbike tires run around 13psi. Maybe some performance road bikes get up to 80-130psi. You'll find most recreational bikes out there are riding around with significantly less.

I always pumped my touring bike to around 110.

Higher pressure means less rolling resistance.