I am trying to install this water filter under my sink in my RV. I am using this Adapt-A-Valve to split off into two lines. One to the current faucet and a new one dedicated to a drinking faucet. The joint going to the nickel-colored female part of the adapter that goes onto the existing valve is what seems to slightly be leaking, slow dripping. I've circled in the picture below where this leak seems to be occurring enter image description here

On the water filter itself, I've switched out the pex insert with a compression-style, this one. The one thing to note on the manual of the water filter is that if you do switch out the insert, to make sure it's NPT threading, for which my understanding is MIP is a type of NTP threading which is what the adapter I bought is. I did about 3 wraps of teflon tape and tightened it as tight as I could. I started with a normal tightness but as it kept leaking I went tighter. Below is an image of where it is leaking from, it appears to be leaking through the teflon tape enter image description here

I am not sure what else to try at this point or where could be the problem, any thoughts are much appreciated!


For the water filter issue, I reapplied teflon tape and added pipe dope and that solved the leaking.

For the first picture on the Adapt-A-Valve, I bought a new one and the same issue is happening with the joint. There were leaks on the other joints and I tightened them up and then the leak moved to the top joint (nickel female side). I might try a different brand


I bought a third Adapt-A-Valve! Interestingly enough, this one came in a box, instead of a bag like the previous two. This one worked without any issue so I'm thinking there were some defect in the other ones

Thank you for all the help!

  • For your update. An o-ring sealed joint should not need to be tightened very much, and in fact, overtightening them can make them leak. So you might be just overdoing that connection if you're trying to treat it as if it were a compression fitting sealing without an o-ring.
    – Ecnerwal
    Mar 14 at 14:20

1 Answer 1


The first one is a threaded connection and I see no sign of pipe dope or tape to make the seal on the threaded connection.

For the second one, you can discover the power of tapered brass pipe threads to split plastic female fittings by just winding it tighter, or you can take it out, clean it up, and try taping again, or change to dope.

Male Iron Pipe (MIP) is a flavor of National Pipe Thread, (NTP) yes. FIP is the other one.

  • The first one has an o-ring inside of the female nickel part so my understanding is that I didn't need teflon tape on that. As far as the actually part that is leaking, that is how the valve came, it was already one piece so I didn't think I had to do anything extra to it. Are you suggesting I remove the threaded piece and put pipe dope or tape on it? If so, I am curious why they sell it as one piece already together
    – User9123
    Mar 14 at 0:13
  • 1
    If it's leaking in the pre-assembled threaded part, contact the company or return it for a different one. That joint, not the one above it with an oring, is where you say it's leaking. And edit those details into the question.
    – Ecnerwal
    Mar 14 at 0:17
  • 1
    @User9123 O-rings are fragile. A nick/pinch/little damage can/will lead to a leak. The good thing is they are easy to replace and can get a kit containing most sizes.
    – crip659
    Mar 14 at 0:18
  • 1
    A hair or a speck of dirt will also defeat O-rings. As will a scratch on the mating surface if you use the wrong tool to remove them.
    – Ecnerwal
    Mar 14 at 0:22
  • 2
    Yes, MIP stands for male iron pipe, which is NPT (National Pipe Thread). I would remove and re-wrap that fitting, maybe 4-5 wraps this time, and reinstall. Mar 14 at 0:24

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