Performance loss regulator with long hose setup?

[beester]

Hi guys... I recently bought myself a 2nd regulator set. Since I dive cold water I chose the Scubapro MK17 / G250V setup.

I asked to interchange the regulator hose with a longhose (5 feet). The shopowner told me that this is not a good idea. Because the volume of the longhose is larger then a normal hose the 1st stage has more difficulty getting the intermediate pressure up again after a breath. According to him this would be noticable in my breathing and would therefore relegate my high end regulator to sub par.

Any truth in this?

 

[Doc Intrepid]

No.

The internal pressure inside a hose is a constant value, along the entire length of the hose. Theoretically there may be a measureable 'recovery time' as hose length increases, while the internal volume rises back up to pressure following an inhalation. But it would take a hose considerably longer than those we're talking about before that period of time was perceptible to a human.

For a 5' or 7' hose, you will perceive no loss of performance at all on a ScubaPro reg.

The guy you met likely has never dived either...



On the other hand, a 5' hose can be a PITA to deal with for other reasons.

But all in all, the guy is giving you a line of crap.

 

[Greg Barlow]

The drop in performance from using a long hose would be so low that a person couldn't notice the difference. As soon as you begin to inhale, the first stage responds to the pressure drop. The high pressure valve mechanism opens, and the gas continues to flow until the first stage pressure equalizes with the surrounding water pressure. Testing has demonstrated that a person cannot tell the difference in a regulator's overall work-of-breathing effort until the difference is in excess of 0.4j/l of energy.

I dive with a long hose system, and cannot tell any difference on inhalation resistance between the 2m hose, and the 0.6m short hose.

Greg Barlow
Former Science Editor for Rodale's Scuba Diving Magazine

 

[Randy43068]

Hi guys... I recently bought myself a 2nd regulator set. Since I dive cold water I chose the Scubapro MK17 / G250V setup.

I asked to interchange the regulator hose with a longhose (5 feet). The shopowner told me that this is not a good idea. Because the volume of the longhose is larger then a normal hose the 1st stage has more difficulty getting the intermediate pressure up again after a breath. According to him this would be noticable in my breathing and would therefore relegate my high end regulator to sub par.

Any truth in this?

Is this the only shop in the area? I'm thinking it's time to find a shop where the owner actually knows something about equipment.

 

[SteveAD]

In fact, just the opposite is true. Over the years, several manufacturers (dacor, US Divers, and mares off the top of my head) have derived higher apparent performance from relatively low end first stages by using an extra large diameter hose. While the first stage can't quite keep up with demand during an inhale, the greater volume of the hose acts as a reservoir of air so the diver doesn't notice the lack and repressurizes during the exhale. Just look at the concept of "snuba" or hooka rigs with hoses in excess of 50 feet, some of them use a standard tank and first stage at the surface.

 

[spectrum]

In fact, just the opposite is true. Over the years, several manufacturers (dacor, US Divers, and mares off the top of my head) have derived higher apparent performance from relatively low end first stages by using an extra large diameter hose. While the first stage can't quite keep up with demand during an inhale, the greater volume of the hose acts as a reservoir of air so the diver doesn't notice the lack and repressurizes during the exhale. Just look at the concept of "snuba" or hooka rigs with hoses in excess of 50 feet, some of them use a standard tank and first stage at the surface.

I was going to say the same thing.....

In pneumatic systems we add accumulators to place a volume of air near the point of use. The long (or big) hose will slow the pressure drop in the LP hose since there is more available volume while waiting for the 1st stage to respond. There is no change in what the 1st stage needs to deliver or what you will draw.

There are effects of moving air through a longer hose but with the large radius of a long hose wrap it's ultra trivial.

Pete

 

[evil_xander]

According to him this would be noticable in my breathing and would therefore relegate my high end regulator to sub par.

Any truth in this?

No, pure BS.

I have the 7 foot hose on my MK25, didn't notice any difference between the regular length and this (it even isn't the ScubaPro 'superflow' or whatever hose, just a generic one).

 

[Luis H]

I agree with Pete and stevead in that the hose can help as an accumulator.

I often use a Scubapro Mk-5 with a Balanced Adjustable metal second stage and a 50 ft hose. I can leave the tank on a pier or on my diving kayak and I can just jump in the water with minimal gear to get some job done. The performance of my BA is just fantastic.

I may noticed a differenced with this rig if I went past 30 or 45 ft because the IP would not be increasing with depth, but we are only talking 15 to 22 psi, so I even dough that it would be noticeable with a balanced second stage.


There are many reasons in pro and con of a long hose, but this is not one of them.

 

[tstonedvr]

I did some airflow test a while back and in fact the long hose improved the regs performance however so slight...I was surprised but it is wahat it is....
Yarg

 

[DA Aquamaster]

Stevead hit it on the nose. The extra volume in the hose acts a s buffer and will reduce or at least slow and delay the IP drop that occurs as the extra volume provides a greater volume of air to draw from.

In fact when I use a scuba regulator with the IP reduced to 10-20 psi to airbrush with and will use a header tank to get the same effect.

Practically speaking, I have done commercial work in water down to about 50' with 100' hose between the fisrt stage on the surface and the second stage at depth. In that case you are not only dealing with a long lose but also about a 25 psi drop in IP relative to the ambient pressure at the second stage due to the lack of any ambient pressure boost from the first stage. Even when working hard under these circumstances, I have never noticed any decrease in performance with a quality balanced regulator.

So...if a shop owner/employee is indicating that a diver would notice a performance decrease from a few extra feet of hose, he or she does not know what he or she is talking about.