How leak tight should your reg and tank actually be?

[Queequeg]

I recently got a new 6.8lb tank and regulator. It's a commercial grade regulator because I was feed up with the quality of those sold through homebrew sites.

Anyway, I have set it up on the tank, with a section of MDPE gas line on the out (JG push fit) connected to a quick disconnect at the other end again by a push fit.

I have checked the whole setup for leaks with soapy water and by submersing the quick disconnect.

I could not see any leaks.

I have opened the tank to pressurize the regulator, with the value closed. i.e no pressure on the gas line side of the diaphragm. then close the tank, trapping the gas between the tank and the diaphragm.

I have left this for 7 days or so. No change in pressure. Happy that the reg is completely leak tight.

Then I repeated this test again, this time with the tank again closed but with 20 psi ups team of the diaghram.

After about 5 days, no change, then there is a drop of about 1 bar on the tank side.

Now this is a tiny loss of gas (in terms of volume) and i can't find a leak on the disconnect tubing or reg. I am wondering is this due to gas permeability of the MDPE tubing when under pressure? especially since this only happens after several days and there isn't a gradual decline.

Could it also be the gauge settingly out? if so why only when the gas is supplied to the line.

What loss is acceptable?

 

[pantherburn]

Any change in ambient temp?

 

[FloppyKnockers]

^^ Was going to ask the same thing. If it gets cold your gauge will read lower.

 

[Queequeg]

Maybe, but not by much. I hooked it up to a keg todaysl so we will see how carbonation goes.

 

[Bowen1911]

Some tank valves will leak slowly if you don't open the valve to 100% so it sits against the upper seal. We had a large oxygen bottle at work go empty in a week because it was only halfway open. Turns out the seal was faulty according to the welding supplier that inspected it.

 

[Queequeg]

I have the value fully open. Also doesn't lose any pressure when the reg value is shut. Suggest it's down stream of the diaphragm.

I can only think it's a tiny leak in the quick disconnect.

I tried a different quick disconnect which when I leak tested by submersing in water had a tiny stream of bubbles.

Though this disconnect isn't visually leaking perhaps it is letting out gas at a slower rate.

 

[JONNYROTTEN]

After 5 days and no leak at 20 psi then a tiny leak (possibly) could be the gauge could be the temps. I would let it ride till the tank is finished and see how long it lasts. Could be chasing shadows

Edit: Missed the quick connect issue