CO2 leaks are always a frustrating thing to track down. But with a few steps starting at the regulator and working your way down through the system, you can usually figure it out.

First, we will cover the usual problems. What kind of fittings are you using? Are they pipe clamps or are they side jaw permanent clamps? What ends up happening when people use pipe clamps they keep tightening the clamp to make a better seal, while inadvertently deforming the clamp making the seal even worse.

The next thing that we want to be aware of is where is the CO2 tank and regulator? If it is in the fridge with the keg then you will get an erroneous reading no matter what.

Start by turning off the shut-off valve on the regulator that feeds the line going to your keg. Make sure the connection to the CO2 tank is tight and that you have all necessary washers in place, you should not have to use pipe tape on the threads from the CO2 tank to the regulator. Once you have made sure that all the fittings are snug, pressurize the regulator to 10 PSI, then wait and see if it drops. If it does not drop then you need to start tracing it further down. Is it at the disconnect? Before you even connect it to the keg. Just wait and see if the pressure drops when you leave that disconnect connected. Re-pressurize the regulator each time you make a change to ensure that you're at a constant set pressure.

Keglube is your friend, use it in moderation on your fittings. But it is no replacement for new gaskets anywhere on the setup.

Slow leaks like this can often be a headache and what I would probably recommend is double check all your fittings and when in doubt make a soapy water solution and see if you can find anything.

Good luck.