7' Hose harder to breathe from?

[DustyC]

Just getting into tech diving and switched to a long hose. My primary 2nd is a ScubaPro A700BT and my secondary is an A700. (Mk25bt 1st)

They've always breathed pretty much identically, but after installing the long hose, my primary is noticeably harder to breathe. Not uncomfortably so, but not the effortless breathing I'm used to. No change in my other 2nd.


Is that normal? Or could I have bad hose?

 

[redacted]

Not normal. Bad hose perhaps. But I'd start with a little adjustment of the cracking pressure on that A700BT.

 

[PfcAJ]

That's weird man. I've got a bunch of regs, some long hose some not. They all breathe pretty much the same.

 

[Akimbo]

Do you notice it on the surface or only at depth. At surface flow rates, it is highly improbable that the difference would be measurable based on the added hose length alone. Very deep can be another story. Does the same thing happen if you swap second stages?

It is possible that some undetected obstruction is in the hose. A botched crimping job on one of the hose fittings or some bit of debris could do it. Try a blind test to make sure it is not some anticipated bias... literally a blind fold and have someone alternate handing you second stages.

 

[KeithG]

Your hose is borked. Or something else is terribly wrong.

Many industrial systems use low pressure pneumatics to operate machines. Industrial jackhammers run at 300 PSI or lower with much longer hoses.

 

[Akimbo]

... Industrial jackhammers run at 300 PSI or lower with much longer hoses.

But also much larger in diameter hoses. The standard ID on a LP hose was found to be a restriction on masks and helmets used for deep saturation dives. Not an issue on the surface. I have seen some strange things happen that restrict flow, thus the suggestion for swapping second stages and a blind test.

 

[DustyC]

Do you notice it on the surface or only at depth. At surface flow rates, it is highly improbable that the difference would be measurable based on the added hose length alone. Very deep can be another story. Does the same thing happen if you swap second stages?

It is possible that some undetected obstruction is in the hose. A botched crimping job on one of the hose fittings or some bit of debris could do it. Try a blind test to make sure it is not some anticipated bias... literally a blind fold and have someone alternate handing you second stages.

I've only had it to 14 feet, I don't remember noticing it in the predive check(but with how I felt that day, that doesn't mean much) but it was obvious at the bottom of the pool. I'm going to check again later toys week.

---------- Post added November 9th, 2015 at 11:52 AM ----------

But also much larger in diameter hoses. The ID standard on a LP hose was found to be a restriction on masks and helmets used for deep saturation dives. Not an issue on the surface. I have seen some strange things happen that restrict flow, thus the suggestion for swapping second stages and a blind test.

Makes sense, I'll try it later this week.

 

[Peter Guy]

Is it possible that an undesired adjustment was made to the second stage when it was attached to the new hose?

 

[divad]

Yeah, switch your second stages and see what happens.

 

[Keith.M]

Check the IP and make sure it is in spec.

I would also suspect the hose.

Your first stage should maintain the correct IP at any depth, so when you are deeper, the actual airflow for each breath is larger. If there is any kind of obstruction in the hose either from a bad crimp job or something physically blocking the flow, it would then get harder to breath the deeper you went.