Thanks for the info! I posted another comment previously, but perhaps it got lost, or maybe it's waiting for moderator approval.
Anyway, I did some more online digging, and I found this great free resource:
The Copper Tube Handbook
Using that resource, and
technical info I found on the Mueller Industries website (the manufacturer of the copper pipe found in home depot). I was able to verify that this copper coil is indeed food safe, though at first glance it doesn't look like it.
The copper coil I bought is listed on the package as type "Refrigeration", instead of type K, L or M. Refrigeration type is also referred to as Type ACR (see
this table).
It turns out that there are a two types of standards that apply to these copper pipes. The ASTM standards, that seem to concern themselves mostly with the strength and thickness of the copper (though I haven't really dug into these standards), and the ANSI/NSF standards that have to do with safety for potable water use.
Specifically, the ANSI/NSF 61 standard is the one to look for, as that certifies the copper tube for use in drinking water systems:
"This [NSF 61] is a health effects standard, which embodies a testing protocol that measures and limits the amount of lead and other contaminants that a device may contribute to drinking water. It also applies to any devices used within the final one liter of volume that exits from a tap or other device. Plumbing fixtures and fittings that comply with this standard are considered "lead-free" and may be used in drinking water systems."
from
Copper.org: Machined Products - Safe Drinking Water Act FAQ
Now, for the Mueller Streamline brand copper tube, only the Type K, L and M tube is NSF 61 certified. This is problematic, since the tube I bought is the ACR or "refrigeration" type. However, I snooped around the
Mueller Streamline Technical information and found the following:
"All tubing produced in Fulton, MS, and Wynne, AR, is seamless and of UNS C12200 grade of copper" (
ref)
Now my copper tube only said Made in USA, but then I found out that all Mueller Streamline copper tube is made in Fulton, MS or Wynne AR (
ref).
Ok. So my "refrigeration"-type copper tube is UNS C12200 grade, and so is the type K, L and M, so it looks like they simply didn't bother with the NSF 61 certification where it wasn't relevant, even though it is the exact same grade of copper tube and thus should pass the certification.
There is one important note, though:
"Please note that devices, and not alloys, are certified under NSF 61. This is because devices, which are constructed of alloys in various designs and configurations, vary in the surface area of any lead-containing alloy exposed to the test water. Thus the various designs of devices, even when made of the same alloy, can leach varying amounts of lead." (
ref)
So, one more check is required: Does Mueller Streamline have a Type K, L or M copper tube (NSF 61 certified) of the same internal diameter as the refrigeration type I bought? If so, then the same surface area of the same grade copper will be exposed to the water (well wort actually), so I can conclude that it's safe. This might be going to extremes, but I figured that I might as well complete the story now that I'd gotten started. I looked at their brochure online, and though my local home depot doesn't carry it, they do make both type K and L pipe of the same outer diameter at least. I suspect that the inner diameter variation between K, L and "refrigeration" types is small if not non-existent.
Out of curiosity I looked up what the UNS C12200 copper grade consists of:
99.90% copper
0.02% phosphorous
(
ref)
Some interesting information about NSF 61:
"Any device, to be certified under NSF 61, is filled with pH8 test water and samples are withdrawn and analyzed over 19 days. In order to pass, the data must insure, with 90% confidence, that 75% of the products examined leach less than 11 ppb lead. Note that this is less than the 15 ppb of lead limit of the Lead and Copper Rule in that the (U.S.) EPA assumes that up to 4 ppb of lead could potentially originate from other sources. In fact, a California Proposition 65 consent judgment has set a lower limit of 5 ppb of lead in that state, as measured according to the NSF 61 test procedure." (
ref)
I take that to mean that NSF 61 certified "devices" sold in California have a stricter requirement of at most 5 ppb lead during the NSF 61 testing, though I am not 100% sure I am understanding this correctly.
The last thing to investigate will be what the pH of wort is (I expect that it's below 7, not above as in NSF 61 testing), and whether or not this pH difference, as well as the near-boiling temperature (I'm using this for a counter-flow cooler), will have any effect on food-safety.
This may seem like a lot of effort to basically verify what was already known, or at least strongly suspected, but I found it a bit suspicious that no-one I asked so far, from home-brewers to plumbers to the brew-master at a microbrewery, had a simple answer such as "these are the copper grades and/or certifications you should look for".
Perhaps I will make a wiki-page on food-safety of brewing materials once I finish investigating the other materials I plan to use.
--
Juul
I'm learning a lot though!
