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I'm in the research stage of building an RO system for an RV, relatively cheaply. I live in the U.S.

The membrane housing has 1/2" FNPT for water intake, and I would like to connect a pressure sensor to the intake. The cheapest pressure sensors seem to be on ebay, but they are all male G1/4. It also needs to handle occasional salt water.

What is the cheapest way to adapt G1/4 to a U.S. standard so that I can find or order parts? Big thank you!

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  • I know plumbing stores have an adapter for the straight 1/4" to 3/8 pipe and 1/2" pipe. The cheap ones would be galvanized more expensive and better for your RO system would be brass. – Ed Beal Jun 22 '16 at 22:43
  • Won't brass corrode in ~4% salt water? I guess it's a matter of how long it takes. However, I can find stainless steel Tees and reducers online readily enough. I'm still not sure why the home improvement stores don't stock SS. – mach Jun 23 '16 at 6:48
  • I dive shipwrecks and find brass that looks brand new if it is in the sand if up out of the sand it looks tarnished. Some of that brass has been down for 50-60 years. The steel and galvanized pipe is all but gone. Pacific ocean, I think it is salt water. – Ed Beal Jun 23 '16 at 13:02
  • I kept re-reading your sentence. That's so cool! It's pretty far "out there" for me - I've only been to the ocean twice in my life. Hoping my future RV will take me more places. – mach Jun 23 '16 at 17:39
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O.P. here. I found NPT sensors on ebay for $8 more than BSPP sensors. The amount of money to adapt BSPP to NPT would cost more.

BSPP Sensor Method #1:

Tee     | SS304 | 1/2" x 1/2" x 1/2" NPT Female        | ~$ 3.00 | Amazon
Adapter | SS304 | 1/2" NPT Male -> 1/2" BSPP Male      |  $11.66 | Ebay
Adapter | SS304 | 1/2" BSPP Female -> 1/4 BSPP Female  |  $12.20 | Ebay
Sensor  | SS304 | 1/4 BSPP Male                        |  $11.20 | Ebay
                                                    Total $38.06

BSPP Sensor Method #2:

Tee     | SS304 | 1/2" x 1/2" x 1/2" NPT Female        | ~$ 3.00 | Amazon
Adapter | SS304 | 1/2" NPT Male -> 3/8" NPT Female     |  $ 5.00 | Grainger
Adapter | SS304 | 3/8" NPT Male -> 1/4 BSPP Female     |  $15.00 | koolance.com
Sensor  | SS304 | 1/4 BSPP Male                        |  $11.20 | Ebay
                                                    Total $34.20

NPT Sensor:

Tee     | SS304 | 1/2" x 1/2" x 1/2" NPT Female        | ~$ 3.00 | Amazon
Adapter | SS304 | 1/2" NPT Male -> 1/8" NPT Female     |  $ 5.00 | Grainger
Sensor  | SS304 | 1/8" NPT Male                        |  $20.00 | Ebay
                                                    Total $28.00
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