What does it mean if IP drops over time?

[guruboy]

Atomic ST1 with matching 2nd stages.

Just had it serviced at a different shop closer to home. Went through the checklist to double check things before using it for a dive this weekend.

Problems-
1) IP fluctuated and would settle between 120-130 after purges
2) IP dropped to 110 when left pressurized by open tank overnight
3) 2nd stage purge needs to be pressed way to far to activate

Im planning to take it back to have them check it again (but do I really trust them now?) to give them a chance to fix things.

The 2nd stage shouldn't be a hard fix so I'm not too worried about that.

Im curious what causes IP to drop over time? The checklist only mentions creep upwards. Seems like this could be a more serious issue.

 

[ajduplessis]

The pressures you provide are between 7.6 and 9 bar, sound on par. What is the IP range for your reg?

 

[jwelburn]

If the reg locked up at the same pressure every time it would be OK, but the fact that it locks up at different pressures after purging is a big red flag. For most regs 120 is a little low to be in spec (this does not apply every reg, and regs intended for very cold water are often tuned this low, but these are more the exception than the rule). 135-140 is more normal Fresh after service a reg should bounce back to the same pressure almost instantaneously, and that pressure should be the same no matter how many times you do it.

 

[tbone1004]

the IP dropping is weird, but it is likely an ever so slight leak in the second stages that isn't enough to trigger the piston to cycle. Drop from 120-110 isn't within the range that will crack the first stage so you might have a leak. That said, I've never seen IP drop over time....

2nd stage purge buttons are a weird thing because you can actually properly tune some regulators and all but disable the purge from the button, but I don't think you can do this on the Atomics.

 

[guruboy]

Slow leak makes sense for IP drop. Thanks.

 

[tbone1004]

keep in mind though, that is VERY slow to only drop 10psi overnight. This isn't something the tech would be able to notice, they typically put it on the gauge and check it for 5-10 mins to make sure it doesn't creep up.

hat said your other concerns are certainly valid and if you aren't satisfied they should fix it

 

[ams511]

The IP fluctuation could be due to the regulator not being cycled completely before you received it. How did it perform after your dives? Normal IP is usually 135 PSI +/- 10. Some techs like to set the IP on the low side to reduce the chance of a regulator freezing.

As far as the dropping IP that is a slow leak and not something to be overly concerned about. This could also be caused be the seats breaking in.

If the purge has to far of a travel that means the lever height was not setup correctly. If you shake the regulator, do you hear a rattle?

 

[guruboy]

I didn't dive yet. Was planning to go this weekend.

I didn't notice any rattling while packing/unpacking/fiddling with the 2nd stage (or 1st).

Already dropped it off at the shop earlier today for them to check out.

 

[knotical]

fwiw, my (old-ish) Atomic documentation says the IP should be 125-145 psi.

 

[ams511]

I didn't dive yet. Was planning to go this weekend.

I didn't notice any rattling while packing/unpacking/fiddling with the 2nd stage (or 1st).

Already dropped it off at the shop earlier today for them to check out.

When a regulator is overhauled besides changing the o-rings the seats are also changed. Without going into detail, the seats needs to be broken in order for the IP to stabilize. This can be done in one of two ways: 1) Purge it over and over again or 2) Dive the regulator. In the future, you may want to ask the shop to use their pool to test the regulators. By the time you use a tank of air the regulators should be settled down.

---------- Post added June 4th, 2015 at 10:13 AM ----------

fwiw, my (old-ish) Atomic documentation says the IP should be 125-145 psi.

The OP says the IP stabilized between 120 - 130 after purging. So that is in the 125 range. Some techs like a lower IP because it helps prevent freezing in cold water. I know Dallas is not especially cold this time of year but lake/quarry water could be in the 40s at depth. Also IP does tend to rise a bit once the regulator is broken in.

I am assuming the 110 reading was with a pressurized regulator on the tank with the valve turned off.