Question "Bouncy" Submersible Pressure Gauge

[JonnieB]

Sounds like restricted air flow. Something is clogged. Did you properly open the tank valve? If this happens with your new SPG too, check the 1st stage.

Yes, tank valves open all the way. It happens with all cylinders. Maybe time for a reg service.

 

[rhwestfall]

myflex HP hose?

 

[ChrisMBC]

Check the reg but also the hose. Most HP hoses have a form of flow restriction built in - the male end of the hose only has a very small hole to allow gas through. If that’s partially blocked, it would cause the issues you describe.

 

[happy-diver]

I've never done this, service my own gear, wash it on a bottle after a dive day, put it on a bottle to dive, and go

A good reason for 2 good breaths before entering the water looking at the SPG not to move.

 

[broncobowsher]

Change the inlet filter on the regulator. The sintered metal is mostly clogged now.
The pressure drop you are seeing is real. The first stage is dropping that much pressure. The HP port on every regulator I have seen is drilled into the passage coming right from the tank valve. But after the filter.

The only other option is the valve is bad. Is this the same tank and valve every time? Is it an old J-valve with a reserve?

 

[tursiops]

I've never done this, service my own gear, wash it on a bottle after a dive day, put it on a bottle to dive, and go

You should, especially if diving from a dive boat with DMs who helpfully "check your valves" when you are not looking.

 

[johndiver999]

Change the inlet filter on the regulator. The sintered metal is mostly clogged now.
The pressure drop you are seeing is real. The first stage is dropping that much pressure. The HP port on every regulator I have seen is drilled into the passage coming right from the tank valve. But after the filter.

The only other option is the valve is bad. Is this the same tank and valve every time? Is it an old J-valve with a reserve?

Would not it make sense to stick an ip gauge on the inflator hose and see if there is a similar and significant variation in the intermediate pressure?

If that were the case, then I would assume the filter would be the cause.

Also I would think that performance issues at depth would be occurring, if the filter is blocked and that does not seem to be the case?

 

[ofg-1]

Try the gauge with another hose. I have seen the lining of a hose come loose and restrict flow to the gauge.

 

[JonnieB]

myflex HP hose?

Yes; those fouling problems with early models from over ten years ago. Also, when I replaced the SPG, no little plastic bits to be seen.

 

[JonnieB]

Change the inlet filter on the regulator. The sintered metal is mostly clogged now.
The pressure drop you are seeing is real. The first stage is dropping that much pressure. The HP port on every regulator I have seen is drilled into the passage coming right from the tank valve. But after the filter.

The only other option is the valve is bad. Is this the same tank and valve every time? Is it an old J-valve with a reserve?

These are rental tanks...different valves/tank each dive. It's been over 200 dives and maybe three years since a service, so several have suggested, like you, the first stage filter may be clogged. After this trip is over, will send it in for service.