I guess it's either in-line bubble counters or 1/8mnpt to bsp then (which is pretty hard to find).

[URL unfurl="true"]https://www.autometer.com/1-8-npt-to-1-8-bspt-pressure.html[/URL]
Not hard but expensive. Think I picked the right gender.

There are some cheaper adapters at grainger. I also found some mnptf x mbsp but I am concerned if mnptf will damage fnpt thread on my needle valve

So I have been testing a regulator. Both stages passed the 6-hour test, no leak. I plugged the out port, charged 2nd stage then turn the knob all the way counter-clockwise and disconnected the regulator from the tank. Then I turned the knob clock-wise but the LPG didnt drop and I didnt hear the discharge sound of the air being pushed back out of the inlet. Any idea what happened ?

not really sure, but I think:
1st stage valve still have problem.
the high pressure co2 pushed through 1st valve, probably a leak, but the low pressure co2 is not released through 1st valve because it is not engaged, and the pressure is low not be able to push through the leak area.

BTW,
this weekend I open three of the same regulators(two matheson 3810 and one prostar 3032), all have problems on the internal, and got them fixed.

How could you fix them? Did you replace any parts? Would it possible to show me how it looks like inside?

So the regulator passed the leak test for both stage. Should I just go ahead and use it? I will do a test where I have the cylinder valve open, charge the 2nd stage and leave it for a while to make sure the pressure downstream wont increase.

charged 1st stage with normal co2 pressure, and if the pressure on second stage not creeping up while the handle is either on or off, the regulator is good to use.


I didn't take the picture, those are not my regulators, I fix them for another hobbyist because I have the tools and know the proper way to have them open.

These prostar 3032/matheson 3810 regulators are original price tag around one thousand dollar a piece, they are complete 316 stainless steel structure, for high purity gas service. Only plastic part inside is high quality HDPE valve seat, rest of the internal parts are 316 stainless steel, and, the inside should be super clean if under the right gas service. A regulator like this will last forever....

So far as I have seen, there is only one reason that they go malfunction, please don't ask me the specific reason, but if you can open the regulator, tighten the internal parts the regulator will be fixed.

Thank you for your advise. Tested both stage charged passed. So I replaced the LP gauge (the one I got before the arrow doesnt point at 0 with no pressure) and hook up the post body. Now the pressure decrease from 44psi to 40psi in 10 hrs (10% in 10hrs). But before that I tested with the old gauge (output plugged) no leaks in 2,3 days. The leak is probably on the new gauge and/or anywhere between the regulator and solenoid (solenoid off). With such a small leak is it worth it to try to find the leak? 4psi decrease in 10hrs I dont know how much co2 I lost.

10% drop in 10 hours, the leaked co2 is not much because the cavity volume in 2nd stage is really small, but since you catch it before the system is put to use, better to take care of the leak, because this leak is small but it is 24/7, will probably shorten your full tank of co2 usage by one or two weeks, or more depends on the co2 tank size and how much you set the co2 flow rate.