Fittings for La Marzocco GS3 plumb-in

September 16th, 2010, 12:25 am

I have a GS3 coming within a couple of days. I would like to have all the fittings needed to connect to water supply when it arrives. The installation manual indicates that included with the accessories is a "L325/L326" stainless steel hose that connects to the pump. It is identified as 1/4G to 5/16. Does anyone know the size of the fitting on the water supply end of the hose?

Cheers, Ken

#2: Post by **CouleurCafé** » January 22nd, 2011, 9:06 pm

1/4" BSPP

Edit: The end that faces the water main supply is 3/8" compression.

#3: Post by **Billc** » January 23rd, 2011, 12:14 am

Ken,
The part number you mention is a hose that goes from 1/4G (BSPP) to 3/8 compression. The 3/8" compression fittings has 5/16" threads on it. Not sure exactly where you live but the 3/8" compression fitting is a popular and standard (you can but it at most any hardware store) fitting in the USA.

Bill C

http://users.rcn.com/erics/ · #4: Post by **erics** » January 23rd, 2011, 10:55 am

The 3/8" compression fittings has 5/16" threads on it

That would be a feat even for Harry Houdini -

Your description of the hose is (obviously) correct but that "5/16" nomenclature is incorrect. Copper tube sizing and compression tube fitting sizes can be very confusing unless you deal with it "day in and day out." As an FYI, a 3/8" compression fitting has 9/16-24 threads.

#5: Post by **CouleurCafé** » January 26th, 2011, 3:31 am

I just measured the diameters of the threaded ends and they are both very close to 1/2" so they must be 1/4". AFAIK La Marzocco only uses BSPP fittings so the braided hose is 1/4" BSPP Female at both ends.
Included are pictures showing that the ends of the hose have brass domes. Not sure if that is a common feature of braided hoses.
Connects to pump

Connects to water supply

http://users.rcn.com/erics/ · #6: Post by **erics** » January 26th, 2011, 4:03 am

Nice pics - thank you.

BUT don't you see the difference in the TPI (threads per inch) of those ends?

The machine end is, in fact, 1/4" BSPP BUT the water supply end will fit a 3/8" compression fitting like a glove. The male matching threads for that 3/8" compression fitting are 9/16"-24.

Yes, the matching male diameters are SIMILAR - 1/4"-19 BSPP has a diameter of 13.16 mm. A 9/16"-24 thread has a diameter of 14.29 mm .

January 26th, 2011, 12:23 pm

erics wrote:BUT don't you see the difference in the TPI (threads per inch) of those ends?

YES! Thanks for pointing that out Eric.

Still, it is puzzling that La Marzocco lists the part specs as "STAINLESS STEEL BRAIDED HOSE 1/4G TO 5/16"-24 UNF"

If I understand correctly, the "5/16-24" is a typo that should read "9/16-24". Right?

http://users.rcn.com/erics/ · #8: Post by **erics** » January 26th, 2011, 12:59 pm

If I understand correctly, the "5/16-24" is a typo that should read "9/16-24". Right?

Certainly, the most accurate answer I could give is "I don't know". What I do know is that 9/16-24 is a valid UNEF thread size for a 3/8" compression fitting and, as Bill C. said it was a 3/8" compression fitting, the answer (and your conclusion) is pretty obvious.

What I also know is that compression fittings of all sizes from 1/4" to 3/8" are "dirt cheap" ($3 each, max) and if I were an owner who had any doubt (you're not in that category now), I would buy a bunch and see what works.

#9: Post by **Billc** » January 26th, 2011, 1:45 pm

Thanks for the correction. I am not houdini just a little tired. If I had thought about it I probably should have realized 5/16 is a bit small for that fitting. Unfortunately I think I was the one who created the text for this part. It is listed in the accessories page in the owners manual and is incorrectly listed as 5/16"-24 and should be 9/16"-24. Because I wrote it I immediately thought it was correct and said so in the post above. The following is a thread list for the compression fittings.

1/8" Compression = 5/16"-24
1/4" Compression = 7/16"-24
3/8" Compression = 9/16"-24

Bill C