Leaky Needle valve with compression fittings

[CanterburyMaple]

Hi - Built my own RO this year (patterned off of this: https://soulyrested.com/2019/01/08/build-your-own-reverse-osmosis-system-for-maple-syrup/) and I'm getting a small leak on the input side of the brass needle valve that I use to control pressure in the system and ratio of concentrate/permeate. This happened when I ran sap at 100 PSI, but didn't happen when I just flushed the membranes with water at 40-60 PSI. I'm no plumber, and tried to search online for what can cause leaks in compression fittings. I added some Teflon tape on the fittings, but that didn't seem to help. Also that didn't seem to be a recommendation. The only thing I saw was to replace the brass ferrel/olive/sleeve with a plastic one, and also put a brass sleeve inside the tubing so the tube doesn't collapse on itself. Any advice? Thanks in advance!

[DrTimPerkins]

Compression fittings do not require tape or sealant, but do need to be assembled and pieces oriented in the correct order and direction. The higher the pressure the more leaks will become apparent.

Secondly, if way overtightened, the seal on the needle valve fitting can fail and will need to be replaced.

[CanterburyMaple]

Compression fittings do not require tape or sealant, but do need to be assembled and pieces oriented in the correct order and direction. The higher the pressure the more leaks will become apparent.

Secondly, if way overtightened, the seal on the needle valve fitting can fail and will need to be replaced.

Thanks Dr. Tim!