Plumbing help - connecting dissimilar fittings

[NervousEnergy]

Trying to connect up a water supply line to my espresso machine without calling out a plumber like last time, though in my defense that was much more complicated and involved setting up a water filtration system and pressure regulator. This new house has a whole home filter/conditioner and is already close to the correct input pressure.

I have water line from the refrigerator water feed that's been T'd for me, with the extra line going to the machine. The standard fridge braided water line is terminated in a typical 1/4" NPT shutoff valve with an empty male connector. The expresso machine has a 3/8" BSW female connector on the end of the plumb-in hose which as a ball-like flare fitting inside the screw cap. Most all of the advice on the 'net about connecting these relates to using plastic tubing and John Guest fittings. I have two very nice brass/metal fittings that need to be connected together - I'd hate to string plastic between them.

Can I use something like this to connect them? 3/8 BSP male to 1/4 NTP Female reducer.

 

[Defenestrar]

The fitting would work fine provided it is machined to the specifications it claims. You'll want teflon tape as both NPT and BSPT are tapered connections and the threads themselves are the sealing component (as opposed to a compression type fitting).

Does your espresso machine need a certain pressure or volume of water to function properly? Which is a roundabout way of asking whether it will work through what the 1/4" line will supply?

Finally, you said "brass/metal fittings." Are both fittings brass, or are you mixing metals here? I can't really imagine the espresso machine using a fitting that would have galvanic corrosion problems being mated to brass, but I thought I should check to make sure you're not mixing metals. Otherwise you really would need to have a plastic (or at least non-conductive) component between the metal fittings.

 

[Deleted member 46272]

I think BSP comes in flared and straight connectors, and I think that adapter you have is NOT intended for flared fittings, and it seems that the espesso machine is expecting a flared male fitting. You may not be able to get a water-tigh connection, and worse, the straight/flat end of the fitting may deform the flared connection on the water line.
Is the line that comes from the machine a solid copper line? If so, another option would be to cut off the British connector and simply use a US-standard 3/8 compression fitting.

- Also the Amazon listing explicitly states that this connector is NOT Lead-free and is NOT intended for drinking water.

 

[Deleted member 46272]

You'll want teflon tape as both NPT and BSPT are tapered connections and the threads themselves are the sealing component (as opposed to a compression type fitting).

Not quite correct. In flared fittings, the male end is cone-shaped and fits into the flaring of the female end. The seal happens inside that flaring. It is critical to get the torque right to get a seal but not to crush the female side of the flaring. Doing so essentially destroys it and the female fitting will need to be cut off and re-done.

Most smaller NPT fittings (like the 3/8 inch faucet hoses or refrigerator water supply lines ) use rubber gaskets for the seal and don't need teflon tape

EDIT - you are correct if both connecters were only tapered, but I think that NervousEnergy's espesso machine is not just a plain BSP tapered thread, but is also a flared fitting.

 

[Carhole]

Flare your own copper line and adapt it. If your machine’s thread is at least compaitbale with brass or copper US parts you can always make pseudo-compression coupling squishing a silicone o-ring between incompatible pressure fittings. At household regulated pressures the forces are tiny and an even lightly closed silicone gap will hold pressure.

 

[Defenestrar]

Ah thanks. I thought it was only straight threads (BSPP) that got flared, but I guess I was wrong. You made me look it up too - so thanks for the excuse to hit Wikipedia I almost never work with Imperial size fittings (as opposed to nearly the American systems in the same units)- if I'm doing international stuff it's typically full metric and more than likely a gas line with Swagelok compression.

I thought the newer US household stuff (sinks, toilets, etc...) that relied on gaskets or compression fittings switched to straight threads (UNC) so there is never any unwanted tension on bringing the mating parts together. Are they actually NPT?

 

[Deleted member 46272]

If your machine’s thread is at least compaitbale with brass or copper US parts

Unfortunately, BSP has totally different TPI (19 tpi vs 18 tpi) - you'll wreck the threads if you try to force them together. Been there, done that, have the (soaking wet) T-Shirt to prove it. I also trying marrying US devices to British plumbing and it ended in tears. This was a couple decades ago, trying to connect a US-sourced water filter to British plumbing. Ugh.

 

[Deleted member 46272]

I thought the newer US household stuff (sinks, toilets, etc...) that relied on gaskets or compression fittings switched to straight threads (UNC) so there is never any unwanted tension on bringing the mating parts together. Are they actually NPT?

As far as I know, they are all FIP - which is the female gender of NPT, they screw onto valves that have MPT connections, and thus also tapered. They just have a big squishy gasket inside that mates up against the NFP male end and then compresses out of the way to allow the threads to snug down. That's why you really don't need to screw those in very tightly or use teflon tape or pipe compound. If you overtighten, you can actually cut through the gasket completely and cause a leak or compress it so much that it shifts out from under the end of the fitting and squishes into the hose/supply line.

NPT - National Pipe Thread Tapered
FPT (aka MNPT aka FIP) - Female Pipe Thread (aka Male National Pipe Thread aka Female Iron Pipe). The female gender of NPT.
MPT (aka MIP) - Male pipe thread (aka Male Iron Pipe). The male gender of NPT.

All of the above are all the same thing and used for both iron pipes (both water and gas) and plastic PVC/CPVC fittings. Then you have "garden hose thread" (literally called GHT), and a bunch of other stuff but if you deal with plumbing in the US, it will be NPT for 95% of it, with the other 4.99% being hose bibs and some appliance hookups and drain outlets that use GHT.

EDIT - well, I was definitely wrong here. Faucet supply lines use straight thread that screw over sink valve "compression thread". I never really looked closed at what that means until today, but it turns out that supply line connections do actually use straight thread, not NPT.

EDIT2: That means that the OP: "The standard fridge braided water line is terminated in a typical 1/4" NPT shutoff valve with an empty male connector." is incorrect. It's more likely that the refrigerator supply line is using "compression thread" couplings, and not NPT/FIP threading. The valve may be sold as "1/2" FIP to 1/4 Compression valve" or somethign simillar, but the "FIP" is the threading that the valve itself uses to connect to the plumbing, but the outlet side of the valve is threaded with "compression thread", which is a different standard.

 

[Deleted member 46272]

Have at it. LOL.
Source: http://fittingsandadapters.com/threadchart.html

Thread Chart​

Dash Size:​

2​

3​

4​

5​

6​

7​

8​

10​

12​

14​

16​

20​

24​

32​

40​

48​

Tube O.D.​

1/8​

3/16​

1/4​

5/16​

3/8​

7/16​

1/2​

5/8​

3/4​

7/8​

1​

1-1/4​

1-1/2​

2​

2-1/2​

3​

Hose I.D.​

1/8​

3/16​

1/4​

5/16​

3/8​

​

1/2​

5/8​

3/4​

​

1​

1-1/4​

1-1/2​

2​

2-1/2​

3​

JIC 37° Flare Thread​

5/16-24​

3/8-24​

7/16-20​

1/2-20​

9/16-18​

​

3/4-16​

7/8-14​

1-1/16-12​

1-3/16-12​

1-5/16-12​

1-5/8-12​

1-7/8-12​

2-1/2-12​

3-12​

3-1/2-12​

SAE O-Ring Thread​

5/16-24​

3/8-24​

7/16-20​

1/2-20​

9/16-18​

​

3/4-16​

7/8-14​

1-1/16-12​

1-3/16-12​

1-5/16-12​

1-5/8-12​

1-7/8-12​

2-1/2-12​

​

​

NPTF Pipe Thread​

1/8-27​

​

1/4-18​

​

3/8-18​

​

1/2-14​

​

3/4-14​

​

1-11-1/2​

1-1/4-11-1/2​

1-1/2-11-1/2​

2-11-1/2​

2-1/2-8​

3-8​

NPSM Swivel Thread​

1/8-27​

​

1/4-18​

​

3/8-18​

​

1/2-14​

​

3/4-14​

​

1-11-1/2​

1-1/4-11-1/2​

1-1/2-11-1/2​

2-11-1/2​

​

​

Flat Face Thread​

​

​

9/16-18​

​

11/16-18​

​

13/16-18​

1-14​

1-3/16-12​

​

1-7/16-12​

1-11/16-2​

2-12​

​

​

​

Code 61 Flange Head O.D.​

​

​

​

​

​

​

1.19​

1.335​

1.50​

​

1.75​

2.00​

2.38​

2.81​

3.31​

4.00​

Code 62 Flange Head O.D.​

​

​

​

​

​

​

1.25​

​

1.62​

​

1.88​

2.12​

2.50​

3.12​

​

​

British Thread BSPP/BSPT​

1/8-28​

​

1/4-19​

​

3/8-19​

​

1/2-14​

​

3/4-14​

​

1-11​

1-1/4-11​

1-1/2-11​

​

​

​

Metric Thread​

10 M10x1.0​

12 M12x1.5​

14 M14x1.5​

16 M16x1.5​

18 M18x1.5​

20 M20x1.5​

22 M22x1.5​

24 M24x1.5​

26 M26x1.5​

27 M27x2.0​

30 M30x2.0​

33 M33x2.0​

36 M36x2.0​

42 M42x2.0​

48 M48x2.0​

​

​

Copper/Nylon Air Brake Thread​

​

​

7/16-24​

​

17/32-24​

​

11/16-20​

13/16-18​

1-18​

​

​

​

​

​

​

​

SAE 45° Flare Thread​

5/16-24​

3/8-24​

7/16-20​

1/2-20​

5/8-18​

11/16-24​

3/4-16​

7/8-14​

1-1/16-14​

​

​

​

​

​

​

​

Inverted Flare Thread​

5/16-28​

3/8-24​

7/16-24​

1/2-20​

5/8-18​

11/16-18​

3/4-18​

7/8-18​

1-1/16-16​

​

​

​

​

​

​

​

Compression Thread​

5/16-24​

3/8-24​

7/16-24​

1/2-24​

9/16-24​

5/8-24​

11/16-24​

13/16-18​

1-18​

​

​

​

​

​

​

​

 

[Defenestrar]

The other way to tell on smaller fittings when the visible taper is more subtle is to feel how they come together.

Straight threads should turn freely until they meet the gasket and then tighten rapidly (I'll echo to not over tighten) - maybe feeling spongey resistance depending on the gasket feel. Tapered threads build in tension after the faces of the threads engage and you continue until it's the right tightness to not leak. (Also shouldn't be over tightened, but that takes even more torque than soft gasket systems).

 

[NervousEnergy]

I think I'm calling my plumber back out... and thanks to Xelas for pointing out that adapter is not lead free. I saw the preceding bullet point about being for faucets and didn't read the next one.

The machine is a German made ECM, and the plumbed supply line it comes with has a flared end with a 3/8 BSP female fitting. Pic showing the fitting dropped away from the flared end:


Machine has been running for around 6 years at the home we just sold, but the water quality there was terrible and the home wasn't well suited for whole house filtration, so I'd bought a softening filter setup from the same company that sold the machine (Clive Coffee). The kit was already well-fitted to the parts that came with the machine - I only had to plumb in the water supply line from the fridge via plastic tubing into the Homeland HWST filter housing. Everything from the filter through the regulator to the machine came with the kit and had correct fittings and went together without any plumbing skill.

This new home I had a full filtration system in before we moved, so I can go directly from the fridge water line to the machine. But now I'm in alien plumbing territory...

This problem and thread is reminding me why I hate all things plumbing. Give me a snarled mess of incorrectly punched/terminated CAT6 wiring to sort through any day...

 

[Deleted member 46272]

I think this:
https://www.chriscoffee.com/products/three-eighths-in-bspt-by-three-eighths-inch-us-maleor
and this:
https://www.homedepot.com/p/Everbil...-Flare-Brass-Adapter-Fitting-800779/207176736... will work.

EDIT: better yet, this:
https://www.espressoplanet.com/BSPP-3-8-Male-to-NPT-3-8-Male-Brass-Fitting.htmlThat "knob" at the end of the line on that photo is the wrong gender for a flared connection. I'm not sure, but I think that is just a "normal" BSPP connector, not flared, and the shape of that knob is to force the gasket out to ensure that it doesn't squeeze inwards when being tightened.

 

[Carhole]

Nice find. No aimless wandering in orange aisles required.

 

[Xenocrates]

I think this:
https://www.chriscoffee.com/products/three-eighths-in-bspt-by-three-eighths-inch-us-maleor
and this:
https://www.homedepot.com/p/Everbil...-Flare-Brass-Adapter-Fitting-800779/207176736... will work.

EDIT: better yet, this:
https://www.espressoplanet.com/BSPP-3-8-Male-to-NPT-3-8-Male-Brass-Fitting.htmlThat "knob" at the end of the line on that photo is the wrong gender for a flared connection. I'm not sure, but I think that is just a "normal" BSPP connector, not flared, and the shape of that knob is to force the gasket out to ensure that it doesn't squeeze inwards when being tightened.

The gender of the knob itself is not that unusual for a flared connection, it's that it's a rounded profile, while a flare joint is distinct and sharp. However, you are correct that it's unusual for the knob to have a the nut behind it, that is more often found behind the pipe that gets flared. Definitely an o-ring sealed hose.

Good deal finding the fitting, especially since from a coffee oriented vendor, it's more likely than a rando HD fitting to be the right standard for a coffee machine. I personally don't like BSPP, given it caused many headaches on a robot for me years back, and I ended up having to find some mildly wonky hose fittings to supply water to a spot-weld gun through the supply harness, because the original order didn't have the right parts to mate up anything, as everything was ordered separately, in many cases by different people and departments.

 

[Deleted member 46272]

...But now I'm in alien plumbing territory...

This problem and thread is reminding me why I hate all things plumbing. Give me a snarled mess of incorrectly punched/terminated CAT6 wiring to sort through any day...

Why do you hate plumbing? You can have a serious conversation about knobs having genders and alien plumbing.

 

[Defenestrar]

Sometimes it's hard to have a serious conversation given some of the terminology - and good luck searching for certain parts on a work computer without violating corporate IT policies.

 

[NervousEnergy]

Yep, that adapter has been ordered, and is on the way. Kind of annoyed Clive didn't have it. Great find! I'm spending a fortune every day at the local coffee shop and it's annoying. Want my precious back in operation...

 

[dmsilev]

Sometimes it's hard to have a serious conversation given some of the terminology - and good luck searching for certain parts on a work computer without violating corporate IT policies.

Are you looking for a full nipple or a half nipple? Can I interest you in our website's custom nipple builder?

I've seen worse in other fields. There used to be this wonderful stuff for stripping magnet wire (with enamel insulation), a goop that you brushed on, waited a few minutes for it to do its magic, and then wiped off. Hard to find now (damn safety regs…), and even harder to safely Google since it was called 'Strip-X'.

 

[The Aloof Alot]

Are you looking for a full nipple or a half nipple? Can I interest you in our website's custom nipple builder?

I've seen worse in other fields. There used to be this wonderful stuff for stripping magnet wire (with enamel insulation), a goop that you brushed on, waited a few minutes for it to do its magic, and then wiped off. Hard to find now (damn safety regs…), and even harder to safely Google since it was called 'Strip-X'.

Try searching Google images for pictures by combining certain sex-related scientific terms with certain plant biology related terms. Even with safe search turned on the results were full of porn. I just wanted good schematic pictures of flowers, FFS!

 

[madmarktech]

Sounds like you're using compression fittings. They sell brass reducers at home depot. You could use a 1/4" to 3/8" fitting. These use "wedding bans" the piece you put on the pipe after the threaded nut. It smashes around the pipe to form a seal. When using plastic pipe, a insert must be used on the inside of the plastic pipe to prevent collapsing the pipe.