Sorry if this is an obvious question, but I have little experience in plumbing and don't want to use the wrong parts.

I'm trying to plumb a European espresso machine to my under-sink faucet water line, with a water filter in the middle. I believe the cold waterline has a standard 3/8" valve. I need to connect it to this under-sink water filter, whose spec sheet states "Inlet and outlet plumbing connections are 3/8” FNPT". The espresso machine has a 1/8" BSP inlet connection.

Here is my current cold water valve: enter image description here

And here is my hot water valve, which seems to already have a 3-way fitting installed to feed something else (but I don't know what it's called): enter image description here

I'm trying to figure out:

  1. What's the exact part name for the 3-way fitting that would work here?
  2. What kind of hose would work to go from the 3-way fitting to the water filter linked above?
  3. What kind of hose would work to go from the water filter to the espresso machine, which has 1/8" BSP thread?

Any other tips on installing this would be greatly appreciated. Thanks!

1 Answer 1


3/8" female NPT is relatively common. You're connecting this filter to your cold water supply valve—correct? Your supply valve is likely 3/8" male compression. So you need a hose and/or fitting to connect that to the 3/8" NPT port on your filter. Probably get a fitting like this: https://www.homedepot.com/p/LTWFITTING-3-8-in-O-D-Comp-x-3-8-in-MIP-Brass-Compression-Adapter-Fitting-25-Pack-HF686625/313501941 (except you don't need 25 of them!) and thread it into your filter. Connect supply and filter with a double 3/8" compression supply hose.

If your supply valve isn't 3/8" compression you'll need yet another adapter.

For the other end, you'll need a way to adapt the 3/8" NPT to your 1/8" BSP. You don't say whether the latter is male or female, so...

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