Bullseye vacuum gauge full bore

How do I use my stock gauge probe from a bullseye vacuum gauge for a vacuum that’s going full bore? What’s the Kf-25 to what?

Thanks you guys.

To a stainless kf25 T, then connect the guage to one side of the T and a Vacuum valve on the other, then the pump to the valve. The guage should read whats in the system, and the valve should let u throttle the vac.
My guage came with a npt thread to it, everytime ive tried to use teflon tape and fit it perfectly into a kf25 to npt reducer, i was unable to get a full vac.( ive tried atleast 10+ times, was never satisfied) Now i use a kf25 to hose barb connection and just put a hose over the npt thread of the guage, it holds a better vacuum then trying to thread it perfectly. Hope that helps

Make sure the guage is facing upwards or else some volatiles may condense in the stainless tube and drain into the gauge.


You can go kf25 to 1/8 fnpt. I have a few of these fittings here.



If youre confident in your fabrication skills then just drill a hole into a spot in the piping you already own and cut threads with one of these 1/8th NPT taps, lil dab of gasket maker, screw in the probe. Ready.


You guys rock! 10 different way to skin a cat and it applies to this. Thankyou so very much.

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BVV sells these and I have it hooked up between my external condenser and my main column of the WFE system I’m putting together- right next to where all the action happens.

Why measure vac at the trap? I wanna know what’s going on where my vapor is moving around the most.


IT helps to place an copper trumpet O ring
Between the npt fitting :grinning:

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