is plastic really safe in saltwater

Discussion in 'Do It Yourself (DIY)' started by keddre, Jul 25, 2017.

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  1. keddre

    keddre Well-Known Member

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    As I look at diy projects (reactors, top offs, etc) they are usually made out of plastic 2 litre bottles. My question is if this is safe? While google isn't showing anyone else showing my concern, I'm worried about the plastic breaking down over time and leaving a large "puddle" on my floor. Thoughts?
    Thanks
     
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  2. Tuffyyyyy

    Tuffyyyyy Well-Known Member

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    I think it should be safe since plastic takes hundreds of years to decompose.
     
  3. Brew12

    Brew12 Electrical Gru R2R Supporter R2R Excellence Award Reef Squad Build Thread Contributor Article Contributor Partner Member 2018

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    Its a difficult question. Not all plastics are the same. Most 2 liter bottles are made from PET which will hold up to salt water just fine. Other chemicals could cause the PET to break down fairly rapidly but I doubt any of them would be reef safe.
     
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  4. Flippers4pups

    Flippers4pups Flipping it since 93 R2R Supporter R2R Excellence Award Reef Squad Build Thread Contributor

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  5. cilyjr

    cilyjr Well-Known Member

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    I did some looking into plastics a while back here's what I found (I wrote this for a thead a whike back)...
    there are 3 types of food safe plastics commonly available on the market.
    1. HDPE (high density polyethylene, recycle code 2) is the most common because of its rigidity. Pretty much all 5 gallon buckets are made of it. it is also what the large brute containers are made from. I use these in the restaurant to store flour sugar ect. and can be bought at any commercial food service suppliers, from home depot, and lowes with caution. it is important to note that NOT ALL HDPE is food safe however. this is because as it is molded, a release agent is sometimes used in the manufacturing to make it easier to remove from the mold. many release agents are toxic.

    2. LLDPE or LDPE (linear low density polyethylene, recycle code 4) is less rigid. Most of your rubbermade containers are made from it. We use these in the restaurant to mix and hold things like coleslaw and large batches of orzo salad ect. these can be bought from commercial food service suppliers, home depot, and lowes and have little risk of not being food safe they are however less rigid (think of a bucket you use to put fall leaves into) and may not be the best for long term storage because of the possibility of becoming deformed. I find containers that use this plastic personally as its cheap and easy to find and because of its flexability it doesn't have the same mold release issues HDPE has. but I do worry about them breaking.

    3. PP (polypropylene, recycle code 5) it might be hard to find a large container made of PP. it is mostly used in those little brown bottles that your prescription pills came in and the disposable ziploc containers with the blue lids that have taken over your kitchen. the issue with PP is The Environmental Working Group classifies polypropylene as a low to moderate health hazard. they state "two substances found to leach from polypropylene labware - an antimicrobial chemical known as quaternary ammonium and a plastic softening agent called oleamide" this might be only because PP is used in some makeup as an ingredient.

    the other plastics i would not use though they are in many bottles one finds food in is PETE (polyethylene terephthalate recycle code 1) as it is known to leach BPA over long periods. and OTHER (other recycle code 7) this really speaks for it self. it is anything that does not fit in the other categories. it could be ok but you cannot know.

    finally vinyl (PVC recycle code 3) strangely not considered food safe due to the use of phthalates to soften the plastic. many companies are using non-phthalate plasticizers since 2010 so it may be changed at some point.

    thats what I found. my curiosity was piqued for both the hobby and my work (a few years ago when the #7 plastic ban happened due to bpa) anyway thats what i found i hope it helps
     
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  6. keddre

    keddre Well-Known Member

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    Thanks, I just learned a ton about plastic that I wasn't expecting. But I also realized that I'm not all that paranoid and that I should use plastic grade 2 or 3, with three being preferred. This actually helped a lot so thanks again
     
  7. cilyjr

    cilyjr Well-Known Member

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    Deleted...double post
     
  8. cilyjr

    cilyjr Well-Known Member

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    Just a side note about pvc it's not common to use on water coming into the home it's more often used for drainage. Water coming in is usually on copper or PEX which is hdpe.

    I believe this is because of a pressure rating under high temps though
     
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  9. bblumberg

    bblumberg Well-Known Member R2R Supporter

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    My laboratory works on the health effects of contaminants from plastics and other environmental sources. With respect to what you note above, I would make some additions and corrections:

    PETE does not leach bisphenol A, it is an entirely different type of plastic. There ARE some clear hard plastics labeled as BPA free that, in fact, contain bisphenol S and bisphenol F, both of which are comparable in their effects to BPA. But these are not PETE. However, there are reports of plastic beverage containers leaching chemicals that interfere with estrogen and testosterone receptor action and some of these must be PETE...

    PVC has both phthalates (small amount) and organotins (quite high amounts), neither of which are particularly good for you. Both leach at relatively slow rates, but the leaching of organotins is detectable and certainly not beneficial. Some of the phthalate replacements (such as tributylcitrate) are also turning out to be problematic. The main problem is that there are few requirements for materials testing before use beyond relatively simple gross toxicity tests that protect you from acute poisoning. Testing for long-term effects is almost non-existent and nearly all safety testing is performed by the manufacturers of the materials themselves.

    Group 7 is a "catch-all" for various types of plastics. It includes some types that you would rather not be exposed to such as polycarbonate (which leaches bisphenol A, particularly when you heat the plastic) as well as modern, biodegradable plastics that are much better for the environment.

    Personally, I would prefer polypropylene and HDPE plastics whenever possible for aquarium water storage as they leach the least amount of miscellaneous stuff. LDPE plastics leach a fair amount of stuff into liquids - for example the "plastic-y taste" which is phthalates for the most part. Having said all this, I use HDPE barrels for my RO-DI water and pump this into an old 45G hexagon aquarium for salt water mixing and storage. The best way to avoid leaching of things you don't want into your water and food is not to store food and water in plastic for extended periods of time.


    Bruce
     
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  10. cilyjr

    cilyjr Well-Known Member

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    @bblumberg Thanks I'll update my note for future reference.

    Could the PETE have been leaching before the bpa scare. Then removed or was my source incorrect? When I found all this it was probably about 4 years ago
     
  11. bblumberg

    bblumberg Well-Known Member R2R Supporter

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    PETE was intended to be a hard clear plastic that can replace polycarbonate - the chemical structure of the monomers is quite different from bisphenol A, which is the monomer of polycarbonate plastics.

    As I noted, a Finnish colleague told me that some PETE beverage containers have raw bisphenol A monomers added for flexibility so it is not impossible that some PETE containers leach BPA, but this is not due to PETE itself. However, I have no direct knowledge whether this is true or not. People who test plastic bottles for the presence of unexpected contaminants have found quite a few. Do a Google Scholar search for Martin Wagner and plastic, for example.

    Bruce
     
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