Hi all! I'm hitting a weird obstacle trying to plumb in this commercial one-group lever. It has a water inlet with a male fitting, next to another pipe with what seems to be the same size fitting, but is capped off. The cap can be screwed onto either position, and I took it to Home Depot and it was a match for ordinary 3/8 brass pipe fittings.

I'm trying to plumb this into my water filter system using John Guest fittings, but nothing I can find seems to match up. The John Guest 3/8NPTF to 3/8 OD won't thread on. I tried 3/8 BSPP but that won't fit either. 1/2 seems to be too big. Is there some other kind of fitting out there that I am missing?

Here's a picture in case it helps anyone figure out what I'm doing wrong here.

My seller says it is a "3/8 conical" and that a hose like this should fit:

https://www.ebay.de/itm/Flexschlauch-An ... 2355502282

Does anyone know if John Guest makes 3/8 conical fittings? I am striking out on a google search.

Maybe there is some other kind of adaptor I can use to hook it up to my system?

Is conical the same thing as flare fittings? Sorry if these are silly questions but I am still working on learning plumbing lingo.

The plot thickens. The seller says the fitting is a 3/8 BSP, but the 3/8 BSP female John Guest fitting I have will not screw onto it. I am just totally puzzled by this. Anyone have any suggestions?

But the cap that goes on either fitting, did fit onto standard 3/8 BSP fittings? That is very puzzling. Do you have means to measure thread pitch to confirm?

The cap went onto 3/8 NPT at the Home Depot, actually. But neither 3/8 BPS or NPT John Guest female fittings will screw on to it. I can sort of engage the threads at first but as I start to tighten it always levers itself to the side and pops off.

I don't have 3/8 BPS in a male thread available to check with, but I can swing by the hardware store and check that out at some point.

If it comes down to it, it appears that the fitting could be removed and replaced with one that works with the John Guest fittings.

From the looks of it, I think you can just use a standard sink or dishwasher supply line.

I believe 3/8" "compression" fittings use 9/16-18 threads. You can check with a standard 9/16" nut to verify.

Cheers!

- Jake

I appreciate the suggestion, but I don't think that's right. I had some spare JG 3/8 compression fittings from where I hooked our water filter into the line feeding the bar sink. They are even smaller than the 3/8 NPT I have on hand, so you cannot even start the threads.

grog wrote:If it comes down to it, it appears that the fitting could be removed and replaced with one that works with the John Guest fittings.

I know it looks liked that is possible, but that's just a nut holding the inlet pipe tight to the bracket coming down from the frame. As far as I can see I'd have to rework a bunch of the machine's plumbing in order to replace this inlet piece, which I'd like to avoid if at all possible.

[creative nickname] wrote:I appreciate the suggestion, but I don't think that's right. I had some spare JG 3/8 compression fittings from where I hooked our water filter into the line feeding the bar sink. They are even smaller than the 3/8 NPT I have on hand, so you cannot even start the threads.

What about 1/2" compression? That would be 3/4-16 threads. One alternative would be that these are metric threads, but that would be be bizarre...

It would be helpful if you could measure the diameter of the nipple.

Cheers!

- Jake