I have a dedicated water filter faucet with a 3/8 female 'compression' supply line (parallel threads). I am interested in connecting a push-fit based filter system to this faucet, but I'm not sure how to connect the push-fit tubing to the faucet. The faucet supply looks like this: enter image description here The most viable option at the moment seems to be the PP051223W stem adapter from John Guest. The problem I see with this is that the threads are NPTF but the faucet line has straight threads. Won't it leak? Is there a better way to connect 3/8 tubing to 3/8 compression faucet?

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1 Answer 1


You will need two fittings to connect 3/8 tubing to 3/8 compression together. Use Teflon tape between the two fittings to prevent leaks, but don't use any on the compression fitting. Remove and discard the brass compression nut and brass compression ring/sleeve to connect your 3/8 hose.

John Guest - Straight Adaptor – Nptf Thread

Part No. PI011223S --- TUBE OD 3/8" --- THREAD NPTF 3/8"


BrassCraft - Compression Female Adaptor

Part No. 66-6-6 --- 3/8 in. O.D. Tube x 3/8 in. FIP


John Guest PI011223S BrassCraft 66-6-6

  • 1
    "Remove and discard the brass compression nut and ring/sleeve" - ehhhhh, that was the key. I should've just gone to the store and poked around. Ended up buying 66CA-6-6XY P at Lowes: lowes.com/pd/… Thanks!
    – autonomy
    Nov 10, 2017 at 15:09

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