Performance loss regulator with long hose setup?

[halocline]

I recently switched to a long hose and actually DID notice an initial cracking effort necessary to draw air from the reg that I didn't notice before. It's an Atomic that has always breathed completely effortlessly. Now, I have to draw slightly harder at the beginning of a breathing cycle before the air comes streaming in.

However, in light of everything that was said above, perhaps it's my reg that needs service. I haven't had it serviced in three years, so that might be the true origin of the issue.

The long hose, if it's working properly, not clogged or kinked or anything, cannot increase the cracking effort of the regulator. Remember that the air in the hose is pressurized, so a larger volume of this air absolutely means less IP drop than a smaller volume with the same demand. Less IP drop 'should' mean lower cracking effort because even in a balanced 2nd stage, there is some downstream bias, so a smaller drop in IP means (net) more force pushing the seat open. Not much, because the balance chamber also drops. I suspect, as you said, you might want to get it serviced. But just to be clear, you didn't try the reg with a short hose, then switch to a long hose, then immediately compare, correct? If that were the case then something wouldn't be making sense to me.

 

[AbyssalPlains]

Thank you for your explanation! Here is what I did: Switched the short hose for a long hose and did five dives thereafter. I dove a doubles rig with two LP tanks for the first time, and didn't notice any difference in reg performance, but also didn't pay attention to whether there might be one. Then I did two more dives with the doubles, didn't notice anything. However, when I used the long-hose assembly on a single 3000-psi tank for the first time, I noticed the increased cracking effort. Of course I know that it can't have anything to do with the tanks, but that's when I started noticing it. It's probably just a coincidence and I should have it serviced soon. I'll go diving again this weekend, and I'll pay attention to the issue.

 

[Randy43068]

Whoever told you that is full $hit. It's total BS. You can figure it out on your own, too. The pressure remains the same in both hoses, the air volume changes slightly. The hose is under pressure, so no it makes no difference at all. The guy is a total nit wit for telling you that. In fact, a 5 foot hose is really too short, it should be 7 feet. But you'll learn that when you practice with the 5 footer. As I hope you do.

Find another dive shop... the guy is ignorant of how a regulator works.

 

[halocline]

The pressure remains the same in both hoses, the air volume changes slightly. The hose is under pressure, so no it makes no difference at all...... In fact, a 5 foot hose is really too short, it should be 7 feet. But you'll learn that when you practice with the 5 footer.

Well, sort of, I guess you're saying kind of what I did, which is that the long hose gives you a larger volume of air at IP to draw from. The pressure is slightly different in the long hose, because it drops less. But I think we're basically in agreement. If anything, the long hose must improve 2nd stage performance, although I suspect it's not anything that would be noticeable.

I do prefer a 5 foot hose for OW with no canister light to the 7 ft. It just routs easier for me. I have both a 5ft and 7ft, I use the 5 ft in OW and the 7ft in cavern/cave.

 

[herman]

My guess is you may have not had the single tank valve fully open, otherwise there is no mechanical reason that the reg would act differently with any tank or hose. Static IP pressures will remain the same, as will cracking pressure. If you want to get technical about it, flow losses (and IP drop) will be greater with a long hose but it's only measurable by machine and does not come close to significant until you get near full flow- like when the reg is in full freeflow. A diver will not be able to detect it, nor could he be able to breath enough gas for the drop to be noticable.

5ft is plenty long for non overhead enviroments, 7 ft is excessive and serves no purpose.

 

[Randy43068]

We are in complete agreement. The IP is roughly 140PSI (give or take depending on depth) so that small difference with hose expansion or volume won't make any difference at all your second stage. It's too small of a change to be discernible to your equipment.

Now dump that 5 footer and get with the program! <chuckling>

Well, sort of, I guess you're saying kind of what I did, which is that the long hose gives you a larger volume of air at IP to draw from. The pressure is slightly different in the long hose, because it drops less. But I think we're basically in agreement. If anything, the long hose must improve 2nd stage performance, although I suspect it's not anything that would be noticeable.

I do prefer a 5 foot hose for OW with no canister light to the 7 ft. It just routs easier for me. I have both a 5ft and 7ft, I use the 5 ft in OW and the 7ft in cavern/cave.

 

[halocline]

If you want to get technical about it, flow losses (and IP drop) will be greater with a long hose but it's only measurable by machine

I don't think so, Herman. IP drop must be less if you are pulling the same demand volume (one breath for example) from a larger volume of gas at pressure. Think of it this way; take a breath from a 100cft tank, take the same breath from a 50cft tank filled to the same pressure. The pressure drop in the 100ft tank will be only half. The long hose is a reservoir of gas at volume just like a tank, except that it gets "filled" automatically by the first stage whenever it drops below IP.

I do agree that the difference is slight enough that no diver will notice it.

 

[herman]

During breathing I agree, I was refering to a constant flow like a freeflow. More hose will mean more loss due to friction when measured at the second stage end of the hose, no way around the friction losses.