I use a Raspberry Pi with water proof temperature sensors fed in through the airlock to measure the temperature of the wort. They are in contact with the wort from pitch and up to bottling, 4-6 weeks.

The website that I buy them from now lists what they are made out of.

The ones I use are PVC (Link). They also have another, more expensive, option for PTFE (Link). The links don't specify whether they are food safe, alcohol resistant, or acid resistant.

I've read conflicting information on whether or not these plastics are A) food safe, B) acid safe, and c) alcohol tolerant.

Are my PVC temperature probes fine, should I upgrade to PTFE, or hope that I have not permanently damaged myself?


Although it doesn't say they are food safe, those plastics are relatively safe at room temperature. Beer lines are made from PVC and PTFE is used a lot in kitchenware. Of course, we don't know exactly how they have been processed/handled, this is still guesswork. No-one here can tell you if they are food safe/acid-safe etc.. just by looking at them.

An alternative to immersing the sensors directly in the wort is to use a thermowell - this will also obviate having to have the sensors wired through the airlock. In various forums, I hear of a number of people putting these sensors directly in the wort. While the manufacturer claims them to be waterproof, some brewers have reported they fail after a few months. I recommend people use a thermowell for long term stability. Also, a smooth stainless steel thermowell is much easier to clean and sanitize than a temp sensor.

(Incidentally, the prices for those waterproof sensors are expensive - you can pick them up on ebay for $1 each.)

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  • Good call on the thermowell! that would eliminate any concern – Ryan Shdo Jan 24 '14 at 8:57
  • I bought a thermowell when I started this project, but the DS18B20 temperature probes were too big for it. Yes, I've seen bundles of 10 DS18B20 water proof probes go for $10 on Amazon; I guess I trust the quality of products sold by Adafruit and figured they wouldn't sell a product for 100% more than competitors without reason.. Hopefully. – Matthew Moisen Jan 24 '14 at 19:07
  • Ah bad luck on the size. Most temp probes are 1/4" 6.35mm OD. The thermowell I linked is 3/8" 9.5mm ID, so there's usually plenty of room. – mdma Jan 24 '14 at 19:23
  • Interesting. As far as I have explored, the DS18B20 probes are the only ones compatible with the RPi that I can just stick into a breadboard. But I don't mind using them and feeding them through the airlock. I forgot to mention that I have been doing this since May/June with on average 2-4 batches going, with swamp tanks that I measure the water of separately, with no failure in the DS18B20s. – Matthew Moisen Jan 24 '14 at 19:26

WOW! good detailed question! I have no actual experience with this specifically but I can sympathise with the chemical/material compatibility question. I have most always had success with searching the great world wide web, with "*** vs. ****", in your case "PVC vs. alcohol" (by the way a search for Polyvinyl Chloride worked better than "PVC").

In the link here I see PVC is compatible with substances of PH levels way outside beer and wine production, so I think you will be ok there, and without reading the whole thing, I am assuming allyl alcohol (on the first page) is way more potent than anything we are creating, so I'm assuming you are good there too! As long as you are within reasonable temps I would say you are just fine https://www.spilltech.com/wcsstore/SpillTechUSCatalogAssetStore/Attachment/documents/ccg/CBOOM.pdf

GOOD LUCK MAN sounds like you got something cool going on, and wish ya the best... keep us posted!

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  • pvc is suitable for beer - it's often used in beer lines. – mdma Jan 24 '14 at 9:23
  • Some PVC is safe for beverages. It depends on the specific formulation of the PVC. The PVC used in beer lines is usually Tygon tubing, which has a special proprietary formulation that is free of phtalates and other plasticizers such as BPA, and it meets FDA, NSF, and other standards. Orindary PVC, such as the type used in plastic cling wrap, contains plasticizers and would not be good for long-term contact with beer. – Chino Brews Jan 28 '14 at 17:25

I am convinced that the answer is that the PTFE probe is definitely safe, and it is unclear whether the PVC is safe, or whether it would leach unknown quantities of pthalates into your beer.

PTFE is the chemical name for Teflon. As we know, Teflon is considered chemically inert and safe for use in food applications, including on no-stick cookware, as long as not heated above 200°F is not applied. Many commenters have suggested a lower safe temp of below 163°F. PTFE is commonly used in other food-grade applications, such as beverage tubing, and in medical applications, such as in hoses and other medical devices (e.g., heart valves). Here is a spec sheet for a type of PTFE tubing, which shows it is chemically inert, and resistant to strong acids. Here is a data sheet from Dupont for Teflon/PTFE, stating that it is safe for food applications under FDA regs.

PVC, on the other hand, often contains plasticizers, such as phtalates (e.g., BPA) or DEHP, that leach into food products and the environment, and are considered to be hormone substitutes (they have hormonal effects on mammals). There are PVC products, such as Tygon tubing (spec sheet) that contain no pthalates and meet FDA and NSF standards for being food-safe. There are also tons of PVC products that contain pthalates. The European Union has been more active in examining the role of pthalates such as BPA in human health. Here is a link to the EU's page on this subject. They have banned BPA for use in products used by infants and children. The FDA has taken a much more laissez-faire approach to the human health issue, but they have, for example, listed DEHP (a product in PVC) as an item of concern.

Link to Wikipedia article on health effects of phtalates: link

Another consideration is that lead is often used in the manufacture of PVC coatings for electrical wires, and California's Proposition 65 requires that fact to be disclosed (link). Lead would not be used in the manufacture of PTFE.

Thus, if I had the choice, I would probably pay the extra $5 for the PTFE version.

Edit: grammar and added links.

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