Tin Leaching from Common Plastic Tubing and a Very Inert Tubing that I Found

Dr. Jim

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I'm sure many of you are tired of me posting about tin leaching from plastic, but for those having "tin problems" this might be helpful.

Although I found tin leaching from many plastic products, I found that plastic tubing may be the worst culprit. I performed "soak tests" where I would soak lengths of tubing (and other plastics) in RO/DI for 5 days then send out water samples for ICP analysis. (Unfortunately, the lengths of tubing and gallons used for soaking varied a little making it difficult to make perfect, direct comparisons, but the end results still remain very significant). Below are 4 plastic tubes that I soaked and the resulting ICP tin results. I also calculated the amount of tin that this would add to a hypothetical 100 gal aquarium (by crude extrapolations from the volumes of RO/Di used to soak the tubes, but not taking into consideration the fact that the lengths of tubing varied. (All tubing had the same pump used to circulate water thru them over the 5 day period; ATI ICP tests were used):

1) Green Tubing (5/8" ID; pump return hose from my tank): 30" soaked in 1.5 gallons....... Tin = 1438; Extrapolated to 100 gal: 22
2) Braided Tubing from Lowes (5/8" ID): 5' soaked in 2 gallons..............................................Tin = 2014. Extrapolated to 100 gal: 40
3) Non-Braided Tubing from Lowes (3/4" ID): 8' soaked in 2 gallons.....................................Tin = 5263. Extrapolated to 100 gal: 105
4) TYGON #3630 (see below); 5/8" ID; 8' soaked in 2 gallons ....................................................Tin = 11. Extrapolated to 100 gal: 0.22

A while back I searched for a more inert plastic tubing and came across a company called Saint Gobain (in PA) who make 30 or more "models" of tubing under the brand name of TYGON. Initially, I could not get their tech support to return my calls or emails and ended up buying one of their "models" blindly on Ebay. But this model (#3603) was too flimsy and after just 4 weeks produced an odd, foul-smelling slime (that I later learned was from a "plasticizer" used in production. (It did, however, leach very little tin as can be seen above).

A few days ago, I finally was able to connect with the company and learned a lot. It appears that TYGON Model #2475 is best suited for our aquarium needs (although there are other models that would also suffice). I was told that there is definitely no tin used in the inner and outer lining of the tubing (but they weren't sure if there is tin in between "but don't believe so". As long as there is none that comes in contact with water then I assume it should be fine).

Unfortunately, this stuff isn't cheap! 10' is the minimum length you can buy @ $8.83/ft (3/4" ID) (plus tax & shipping). But because of all my tin problems and dying SPS, I bought some which will be delivered tomorrow. Eventually, I may do a soak test on this tubing, but probably only if my "tin problem" persists. I bought it here: 3/4" ID x 1" OD x 1/8" Wall Tygon® 2475 High-Purity Tubing | U.S. Plastic Corp.

You can read more about this tubing here:
2475.pdf (usplastic.com)

Hope this might help anyone "suffering" from tin issues! :)
 
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Dr. Jim

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This is interesting. It looks like none of the tubing types you tested were designed for aquarium use right?
Not sure what you mean by "designed for aquarium use." What tubing is actually designed for aquarium use? Actually, the green tubing came with my aquarium which is made by a well-known tank manufacturer. Two of them are the common tubing that is sold by Lowes or Home Depot. I'm sure there are many reefers that use that tubing. No?
 
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Wonder how this stuff would rank
 

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Im not getting tired! I was actually looking forward to it. Great job!

Is the tubing just regular vinyl tubing? Got pics?

Id love to do an icp on pvc pipe!
 
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Dr. Jim

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To answer some of the questions above.....
First, although I've spent a lot of time researching plastic tubing I am certainly not an expert in the field; however, I may be able to present some practical suggestions and thoughts:

I am very confident that the Tygon 2475 will prove to solve my tin problem and will be found to be far superior to common vinyl tubing. The only "negative" that I see is the cost. For me, it was worth purchasing after 1 year of "tin nightmares" and frustration. A 10' length with tax and shipping came to $11.12 per foot..... more that the cost of a T-Bone! So, the only reason I see to try to find an alternative would be because of cost. I'm not concerned about doing this right now, but for anyone that wants to pursue this, here are some things I would look for:

a) Many advertise "excellent resistance to chemicals" but I don't think that is what we want. Those tubes are being protected from chemicals and may contain unwanted ingredients to do so. It is more important to find the term "inert" or "high purity" which suggest that chemicals won't leach.
b) "Meeting FDA criteria for Food and Beverage Processing" seems to be a promising quality.
c) USP CLASS VI: This is the most rigorous testing category aimed to certify that there are no harmful reactions or long-term bodily effects caused by chemicals that leach out of plastic materials. USP Class Testing standards are determined by the United States Pharmacopeia and National Formulary (USP-NF), the organization responsible for the quality and safety of medical devices and foods. Class testing is frequently conducted on plastic materials that come in contact with injectable drugs and other fluids found in various steps of the drug manufacturing process. (Tygon 2475 meets USP CLASS VI criteria).
d) "Does not contain Plasticizers" is essential.
e) Durometer (Shore A): This is a measure of the firmness of the tubing. The higher the number, the more firm it is. For example, the first Tygon 3630 I bought that I said was too "flimsy" was #55. The Tygon 2475 is 72.
f) My guess is that any comparable tubing will be at least almost as expensive. (Like anything else, you get what you pay for).
g) Above all, contacting technical support at the company to explain your proposed usage and specifically questioning whether the product contains tin might be one of the most important steps.

@Malcontent: To answer your question about silicone....I really don't know. I can say that Tygon has charts comparing their product to silicone and of course they make silicone look inferior. But I think the more important thing would be to follow the steps I outlined above. (I doubt that just because it is silicone it would mean there is no tin).

Although I don't think there will be anything too exciting about a photo, I will post one after my tubing arrives. :)
 
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I think silicone has some advantages. One being that it doesn't use plasticizer and should stay flexible. There are quite a few types of medical grade silicone tubing if you want extreme purity.

Conventional silicone tubing:


Reinforced or medical grade:

 
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Dr. Jim

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I think silicone has some advantages. One being that it doesn't use plasticizer and should stay flexible. There are quite a few types of medical grade silicone tubing if you want extreme purity.

Conventional silicone tubing:


Reinforced or medical grade:

You just need to find if they leach tin. Easier said than done though, unless tech support can affirm that or if you perform an "ICP soak test" like I have been doing.

I just took a quick look at the Silicone Medical grade and it is rated with a Durometer hardness of only 60. I think we would find that too flimsy. (Again, I found 55 to be ridiculously soft. OK only for a straight run.)

Quickest avenue might be to call Silicon and try to get the needed info.
 
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Dr. Jim

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Tygon2475 just arrived. It looks nice. Nice firmness and perfectly round (unlike slightly flattened tubing from Lowes; more firm than Lowes tubing also). I can coil it to a 8" diameter with out it trying to fold. Almost has a silicone-like feel to it, but firm. Very slightly white opaque, (Blue tinge in photo is from aquarium light). Not sure what else I can say........ looks expensive! :) (someone was nice and cut me an extra 2' 4"..worth about $26 for the extra amount. Some guy in the back must have felt sorry for me!) :)

Tygon.jpg
 
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Now you've got me worried. I used the braided stuff from lowes.
If you have been using it for a while and your SPS corals are fine, then perhaps you don't have to worry. I only have a few LPS. Two Rose Corals never seemed affected even by high levels of tin. Two favia could have been affected. At any rate, the true test would be to run an ICP and see if you have tin. If so, the Lowes tubing should be a highly suspicious.
 
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Would soaking it in acidfied water remove it?
I don't know for sure but I doubt it. Also, keep in mind that if the plastic tube has tin in the formulation, it will be throughout the whole thickness so as the tube "wears" (if that is possible) there probably will be "new" tin exposed. The same may be said of PVC pipe. I mention this because many have written that over time the tin leaching from pipes/tubing diminishes. I'm not sure if that is true because of the reason I just stated and in my "experiments" I found tin leaching for at least a year in some cases. (I set up my tank exactly 1 year ago so I don't have data for time-frames longer than that).

This differs from glass which has a "layer" of tin only on the surface (as opposed to throughout the entire thickness like with tubing and PVC pipes). So, if glass is leaching tin, I would expect that eventually it would diminish. (I found no tin leaching from my MT or glass sump after performing "soak tests.")
 

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Thanks so much for your sharing Dr. Jim

My tank is 8 years old. ICP tested in 2019 was fine. But in October 2020 tin was too high (17.39ug/l). Many of hammers, frogspawns, torches polyps were dropped out of the skeleton. Maybe high tin is a culprit

I don’t know where it’s from, headache.

Any advice?
 
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I'm sure many of you are tired of me posting about tin leaching from plastic, but for those having "tin problems" this might be helpful.

Although I found tin leaching from many plastic products, I found that plastic tubing may be the worst culprit. I performed "soak tests" where I would soak lengths of tubing (and other plastics) in RO/DI for 5 days then send out water samples for ICP analysis. (Unfortunately, the lengths of tubing and gallons used for soaking varied a little making it difficult to make perfect, direct comparisons, but the end results still remain very significant). Below are 4 plastic tubes that I soaked and the resulting ICP tin results. I also calculated the amount of tin that this would add to a hypothetical 100 gal aquarium (by crude extrapolations from the volumes of RO/Di used to soak the tubes, but not taking into consideration the fact that the lengths of tubing varied. (All tubing had the same pump used to circulate water thru them over the 5 day period; ATI ICP tests were used):

1) Green Tubing (5/8" ID; pump return hose from my tank): 30" soaked in 1.5 gallons....... Tin = 1438; Extrapolated to 100 gal: 22
2) Braided Tubing from Lowes (5/8" ID): 5' soaked in 2 gallons..............................................Tin = 2014. Extrapolated to 100 gal: 40
3) Non-Braided Tubing from Lowes (3/4" ID): 8' soaked in 2 gallons.....................................Tin = 5263. Extrapolated to 100 gal: 105
4) TYGON #3630 (see below); 5/8" ID; 8' soaked in 2 gallons ....................................................Tin = 11. Extrapolated to 100 gal: 0.22

A while back I searched for a more inert plastic tubing and came across a company called Saint Gobain (in PA) who make 30 or more "models" of tubing under the brand name of TYGON. Initially, I could not get their tech support to return my calls or emails and ended up buying one of their "models" blindly on Ebay. But this model (#3603) was too flimsy and after just 4 weeks produced an odd, foul-smelling slime (that I later learned was from a "plasticizer" used in production. (It did, however, leach very little tin as can be seen above).

A few days ago, I finally was able to connect with the company and learned a lot. It appears that TYGON Model #2475 is best suited for our aquarium needs (although there are other models that would also suffice). I was told that there is definitely no tin used in the inner and outer lining of the tubing (but they weren't sure if there is tin in between "but don't believe so". As long as there is none that comes in contact with water then I assume it should be fine).

Unfortunately, this stuff isn't cheap! 10' is the minimum length you can buy @ $8.83/ft (3/4" ID) (plus tax & shipping). But because of all my tin problems and dying SPS, I bought some which will be delivered tomorrow. Eventually, I may do a soak test on this tubing, but probably only if my "tin problem" persists. I bought it here: 3/4" ID x 1" OD x 1/8" Wall Tygon® 2475 High-Purity Tubing | U.S. Plastic Corp.

You can read more about this tubing here:
2475.pdf (usplastic.com)

Hope this might help anyone "suffering" from tin issues! :)
I wish you luck with your tank - and its great to see an experiment. I would like to hear your thoughts on the following though:

1. you only sent 1 sample - and given the variability I've seen with ICP tests - I'm not sure you can trust the differences between brands. (I know - it would be prohibitively expensive to send multiple ICP tests)
2. as you said - the lengths were different - which would mean that the 30 inch piece as compared to the 5 foot piece may leech a lot more. Also the diameters were different - its fine - they all have measurable tin - but - it just makes it hard to compare different ones
3. You used RODI - its not RODI in our tanks.
4. I wonder if you put the tubing in water for a week - then rechecked the test - with fresh water - if the tin levels would be significantly lower (i.e. - I would think that the same levels of tin would not be leeching out week after week) - but in any case it would be interesting to think about.
5. I've heard the same theory about PVC leeching tin. (and also that over time this stops)
6. Hopefully you will measure the new Tygon tubing that you got to see if it has the same amount as the one you tested.

In any case - thanks for doing the experiment
 
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Dr. Jim

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Thanks so much for your sharing Dr. Jim

My tank is 8 years old. ICP tested in 2019 was fine. But in October 2020 tin was too high (17.39ug/l). Many of hammers, frogspawns, torches polyps were dropped out of the skeleton. Maybe high tin is a culprit

I don’t know where it’s from, headache.

Any advice?
From everything I learned, I have to say consider tubing first, followed by PVC pipes or any plastic especially if tin is the ONLY metal elevated. (If other metals are elevated, I would consider corroding metal). Was the same ICP company used for both tests? Which one? (ATI tends to show higher levels than Triton, IME.....sometimes much higher).
 

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From everything I learned, I have to say consider tubing first, followed by PVC pipes or any plastic especially if tin is the ONLY metal elevated. (If other metals are elevated, I would consider corroding metal). Was the same ICP company used for both tests? Which one? (ATI tends to show higher levels than Triton, IME.....sometimes much higher).
Thanks for your reply

- Yes, tin is the only metal elevated
- Yes, ATI did both tests

Few days ago I did water change 25% x 4. Now must change all PVC and flexible tube?
 

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