Converted Commercial RO - Leaks & Troubleshooting.

[USinCA]

Ran my converted commercial water RO this past weekend. I'm getting 0.75gpm permeate and 0.3gpm concentrate at 200psi, with 32 degree sap. Going from 3 to 8.2 brix. I'm quite happy with that!
But, I have a few stainless fittings leaking. I used 4 wraps of grey stainless tape on all of them, but they probably got backed off a bit while assembling. Do y'all use tape or dope or both on SS fittings? Is not backing off the key?

Also my membrane housing (stainless with black end caps), burps out a bit of liquid on start up until pressure builds, is this normal or do I need to replace the O rings?

[Bucket Head]

I'm not familiar with black-capped ends- is it an o-ring or a "cup" style seal? I have cups and they will sometimes leak a little upon first startup. They need presssure to seal, its how they work. Sometimes I have to turn my end caps a little to help get them to seat a little better. (with machine off and no pressure) I would try to turn your caps a little to see if the rings, or cups, seat a little more even.
It's best not to back off fittings, but sometimes it can't be helped. Put a little dope on the threads along with the tape- but not a lot! It's thread sealant, not frosting. You don't want it all over the place and you really don't want excess sealant in the machine. Wrap the tape and then put a thin coat of the other on. Good luck.

Steve