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Protecting PVC from UV 5

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uluru

uluru

Civil/Environmental
Joined
Jun 18, 2012
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Hello all,

I'm about to start working on a project overseas that is using rainwater harvesting systems for drinking water. The thing is, they use PVC gutters to collect the water from the roofs. The water is passed through a ceramic filter to deal with some biological contaminants, but I know that UV can degrade PVC. I haven't read anything specifically about how the degradation might affect the water supply (i.e. what kinds of toxins or carcinogens might be washed into the system).

When looking up UV protection for PVC, I read about water-based latex paints, which seem like they could pose their own issues if used on these gutters. Does anybody know what the exact danger is of having these exposed PVC gutters, and/or does anybody have suggestions for how to deal with the problem?

Thanks for your help!
 
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PVC pipe can incur damage when subjected to long term exposure to ultraviolet radiation from sunlight. Unless specifically formulated to provide protection from UV radiation, PVC pipe is not recommended where it will be continuously exposed to direct sunlight.

UV degradation occurs when energy from the UV radiation causes excitation of the molecular bonds in the plastic. The resulting reaction occurs only on the exposed surface of PVC pipe and penetrates the material less than 0.001-Inch. Within the affected zone of reaction, the structure of the PVC molecule is permanently altered with the molecules being converted into a complex structure typed by polyene formulations. The polyene molecule causes a light yellow coloration on the PVC pipe and slightly increases its tensile strength.

UV degradation results in color change, slight increase in tensile strength, slight increase in the modulus of tensile elasticity and decrease in impact strength in PVC pipe. PVC pipe becomes brittle.



It is unlikely that water contamination from sunlight exposed PVC has ever been studied. It is also unlikely that any significant water contamination occurs as contamination from PVC water transmission piping has not been known to be recognized as a major health and safety issue.

Modern latex paint is water-based, non-hazardous, and generally considered to be low in toxicity. An exception would be paint that contains mercury or other heavy metals to provide mildew resistance. Latex paints cure by a process called coalescence where first the water, and then the trace, or coalescing, solvent, evaporate and draw together and soften the latex binder particles and fuse them together into irreversibly bound networked structures, so that the paint will not redissolve in the solvent/water that originally carried it. The residual surfactants in paint as well as hydrolytic effects with some polymers cause the paint to remain susceptible to softening and, over time, degradation by water.


Your best option is probably to use PVC that has a UV inhibitor if you can find it. The gray electrical conduit is suitable for continuous exposure to the sun.

A final thought is that one would think the biggest health and safety issue that you should be concerned with will be from bird and animal feces.
 
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Actually, per some 21st century reports by King Faud University researchers et al at (including I think one test site in Florida), in addition to structural effects already mentioned sun or heat exposure in quite non-obvious fashion reportedly can also make at least pipe leach more carcinogenic vinyl chloride monomer and other stuff than
normal from the walls of pvc pipe into previously potable water conveyed within said pipe (e.g. see mention of this research and results at page 759 of paper at
etc.) [While I say non-obvious, I guess this may not be surprising to folks who have tried to drink out of a vinyl water hose or plastic bottle that has been laying out in the sun.]
That being said, I wouldn't be surprised if the stuff bimr mentioned at end wouldn't get folks at least quicker and more noticeably without precautions concerning same, and I guess someone might additionally make a sort Faustian value judgment
( that being able to lay ones mouth on moisture in some areas might outweigh arguably lesser or less immediate risks!
 
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Any vinyl chloride if present from gutter oxidation is quickly oxidized by exposure to air and the sun.
 
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While I have oftentimes heard that argument associated with volatile or plastic contaminants, I suspect there are at least some however who might wonder if that necessarily wipes the slate clean (so to speak) in the long run. If folks care to make the time, a recent document on a site maintained on the Centers for Disease Control in Atlanta, Georgia at is an interesting read. While along with some copy and cited research that perhaps minimizes concern in some areas (no doubt well financed by the industry), I noticed however the kind of interesting summary way down on page 195,

"Vinyl chloride has been detected in air (Baker and Mackay 1985; EPA 1979a; Fishbein 1979; Gordon and Meeks 1977; Stephens et al. 1986; Wood and Porter 1987), water (Burmaster 1982; Cotruvo 1985; Dyksen and Hess 1982; Goodenkauf and Atkinson 1986; Stuart 1983; Westrick et al. 1984), sediment (Wang et al. 1985), and food (Gilbert et al. 1980; Williams 1976; Williams and Miles 1975). Intake data for the general population from the various media are available (EPA 1979a, 1985b; Gordon and Meeks 1977; Westrick et al. 1984). Data on levels of vinyl chloride in soils are needed. Site-specific data on concentrations of vinyl chloride in air, soil, and water would be helpful in estimating the risk of exposure for populations living in the vicinity of hazardous waste sites. Also, current data on the extent of release (if any) of vinyl chloride from PVC pipes and from car interiors are needed to estimate the risk of exposure of the general population."

It would appear that maybe not everything has been conclusively "studied" when it comes to this stuff. One thing is for sure, it appears there is a whole lot of it, and now in a whole lot of places. The last column of Table 6-2 beginning on page 175 publishes a "Emission density (pounds/year/square mile)" of vinyl chloride by USA state. I noticed the values are in some states in the pounds per square mile magnitude; e.g. in the state of Texas alone there were 3.22 pounds of vinyl chloride emitted in 1996 PER SQUARE MILE in the entire state. For those of us familiar with the state, we know there are of course a good many square miles in Texas! I think you can
furthermore rest assured this published total does not include emissions from a no doubt now goodly quantity/surface area of finished products like pvc gutters, sidings, or even pipes etc. that are sitting in the sun and heat (and by at least some recent research are being affected by same). And this doesn't include any concerns of "end of life" issues.

"Plastics my boy, Plastics."
(while I'm sure long before the time of many readers now on these
forums, career advice given to young Benjamin Braddock in the 1967
movie "The Graduate")
 
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So the takeaway is: this could be a big problem, but we're not sure. If I coat these gutters with a latex-based paint, will the vinyl chloride problem be solved? I'm really wary of painting something that will transport water for human consumption, but it seems like that may be a solution?

That said, this link suggests that PVC gutters for RWH systems are fine, and then has something about filtering the water for human use:

makes it seem like it's ok to use PVC for gutters. I'm not sure what to do - the gutters are in a rural location and budget is tight. I think that's why we didn't have metallic gutters to begin with, but I'm just joining on this project now.
 
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to uluru,

There is no issue with vinyl chloride. rconner's comment has more to do with his advocacy of metallic piping systems than with vinyl chloride. This is just another opportunity to denigrate pvc piping.

to rconner,

Appreciate your comments. However, in this particular instance, they are irrelevant to the topic.

Quoting from your first reference (Baker and Mackay 1985; EPA 1979a.)

“Page 3 How might I be exposed to vinyl chloride?”

“Vinyl chloride is not normally found in urban, suburban, or rural air in amounts that are detectable by the usual methods of analysis. However, vinyl chloride has been found in the air near vinyl chloride manufacturing and process plants, hazardous waste sites, and landfills.”

To extrapolate vinyl chloride exposure from references that are mainly dealing with major releases from vinyl chloride manufacturing and process plants, hazardous waste sites, and landfills is quite a stretch.
 
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I guess when more than one side of any particular issue is expressed, it may be popular to attempt to discredit the messenger as opposed to the message, particularly when there may be some discomfort with same. I personally think debate on many subjects could be of value in the long run, and I don’t discourage the free exercise thereof. While there are of course effects of manufacturing and disposing etc. of anything including immediate cost and otherwise, with all due
respect I believe all building materials including gutters, pipes or whatever must be manufactured, service, and then be recycled or disposed of at the end of their useful life. In my opinion, none of these issues are irrelevant to their selection. That useful life has furthermore at times been far less for some materials than others in some applications.
As to the comment, “To extrapolate vinyl chloride exposure from references that are mainly dealing with major releases from vinyl chloride manufacturing and process plants, hazardous waste sites, and landfills is quite a stretch”, while I guess some folks live and work in more remote areas, with a perception of less effect or someone else(s) problem, I know there is a quite recent study that looked at proximity of population to just known Superfund sites in the USA and
Puerto Rico now posted at
Some reported deliverables of this study are as follows:

1) The estimates of total residential population in 2000 living within a 1-mile buffer of National Priorities List (NPL) Superfund sites (1634) in the United States and Puerto Rico include 13,217,736 (SF1) and 13,214,375 (SF3).
2) The estimates of total residential population in 2000 living within a 4-mile buffer of National Priorities List (NPL) Superfund sites (1634) in the United States and Puerto Rico include 74,727,924 (SF1) and 74,726,099 (SF3).
3) The number of children under the age of 5 in 2000 living within a 1-mile buffer of National Priorities List (NPL) Superfund sites (1634) in the United States and Puerto Rico is 972,459 (SF1).
4) The number of children under the age of 5 in 2000 living within a 4-mile buffer of National Priorities List (NPL) Superfund sites (1634) in the United States and Puerto Rico is 5,226,990 (SF1).
5) The number of people over the age of 65 in 2000 living within a 1-mile buffer of National Priorities List (NPL) Superfund sites (1634) in the United States and Puerto Rico is 1,510,549 (SF1).
6) The number of people over the age of 65 in 2000 living within a 4-mile buffer of National Priorities List (NPL) Superfund sites (1634) in the United States and Puerto Rico is 8,959,837 (SF1).
7) The estimate of the residential total population living within 1 mile of two or more NPL sites is 1,465,121 (SF1).
8) The estimate of the total residential population living within 4 miles of two or more NPL sites is 28,976,895 (SF1).”

I guess proximity to perhaps more generic “landfills” might draw in a few more folks. When some happen to be close to some longtime chemical/plastic manufacturing areas, the concerns may be much more visible, e.g. as is prominent as we speak in the news this week at e.g.

As to prospects of painting pvc gutters, I’m not sure that would not work but have heard that there have been past problems with attempts of painting some pvc items (having to do with adherence, durability etc.), and of course one might have to think about NSF61 or other applicable potable water contact certification etc. for the system.

There are of course other types of basic gutter etc. materials, but I don’t know all their pros and cons as well in the context of a potable
water collection system.

good luck with the interesting project and everyone have a good weekend.
 
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The poster is talking about gutters here, not

The report states:

"The amount of vinyl chloride migrating from rigid PVC water pipes into drinking water was directly proportional to the residual level of vinyl chloride in the pipe itself. In 2000, the National Sanitation Foundation (NSF), at the request of the Vinyl Institute, conducted a study on the levels of residual vinyl chloride monomer found in PVC pipe and fittings (Borelli et al. 2004). This report concluded that 86% of the PVC pipes and 88% of the fittings had no detectable levels (detection limit of 0.1 mg/kg) of residual vinyl chloride monomer."

In addition, the reports states

"When released to the atmosphere, vinyl chloride is expected to be removed by reaction with photochemically generated hydroxyl radicals (half-life = 1–2 days)."

A reasonable person would conclude that the message is that no one should be concerned about vinyl chloride exposure from pvc gutters.

 
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rconner,

Some of your posts have meaningful information however the dogma you have for ductile iron is again evident. When you go off topic it becomes plain that you are pushing the all too familiar barrow.

Please disclose once and for all if you are paid to advocate metallic products so that the memebrs of this forum can gauge for themselves where you are coming from. Are you a paid official of DIPRA or any other organisation? If so, have the decency to put you title below your signature.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
 
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The quote provided by bimr, "This report concluded that 86% of the PVC pipes and 88% of the fittings had no detectable levels (detection limit of 0.1 mg/kg) of residual vinyl chloride monomer" is indeed written in the positive. The unstated contrapositive though is that 14% of this apparent 21st century/modern generation pvc pipe and 12% of the fittings did impart at least a certain small amount of vinyl chloride into the water inside. Unless the consumer is assured by actual testing at their tap, I'm not exactly sure they are not drinking some of this stuff.
I guess the hope is the small amount they may be getting from this source, and cumulative amount from whatever/all other sources as previously explained, are not in the long run harmful to them or their families. Altruistic questioning of motives and "decency" of a poster revealing same may be fun for some, but I prefer to keep discussions on technical issues.
 
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"Current certification standards regulating the residual level of vinyl chloride monomer in
polyvinyl chloride pipe are sufficiently stringent that significant vinyl chloride exposure from
leaching into drinking water is not likely (CMA, 2000)."


CMA (2000). Personal communication. Letter from C. Price, Chemical Manufacturers
Association dated March 14, 2000.
 
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rconner's at it again.
rconner, you quite clearly are paid to advocate ductile iron pipe and denigrate other types of pipe.
Why will you not admit it?
You imply that you are offering unbiased, "technical" information, but this is clearly not the case.
 
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PVC also has a fairly high coef of thermal expansion... You may want to look into some work done by PARC and centrifugal filtration.

Dik
 
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As to the statement of another on this thread, “There is no issue with vinyl chloride”... If true I guess this profound statement would be welcome news to e.g. the citizens of Doniphan County, Kansas, who 20 years ago found they had been drinking (or aerosol breathing? some of the stuff for a great many years, then found out again that some were still drinking it six years later in 1998 (see long after assurances the problems, or at least considered such then, were supposedly handled by regulators and industry folks several years earlier). It would also be welcome news to taxpayers, who per the report under “Section 1431-Emergency Powers Section” at apparently funded replacement of then offending infrastructure there and elsewhere. It would be welcome news also to the countless customers of all the other utilities in at least seven states, who found at the time of at least some testing at Customer’s locations in very early 1990’s (even if there has been much less testing actually at tap, or away from water source after passing through pipes, since?)they were also drinking same. It would be welcome news as well to the consumers in 121 utilities and 27 states per the site at who have been found (even with limited testing) to have vinyl chloride in their drinking water just since 2004. I guess it would also be welcome news, though perhaps a hard-sell in the present day, to some citizens of Mossville, Louisiana in the very recent news as I previously mentioned. To all those hordes in the absence of any testing at the actual tap who really do not know whether or not they have been exposed to it, I guess this would be proof of the old adage, “what they don’t know won’t hurt them.” This would perhaps be bad news however for attorneys(barristers) e.g. see
who describe the substance on their site as follows, “The polymer of vinyl chloride has been described as one of the most hazardous products for human health ever created. “

I guess the only question remaining is why then have all these doctors spent all this time and effort on all these advisories and pleas, and why does the USEPA also set the Maximum Contaminant Level Goal (MCLG) for this substance at ZERO (and other levels not a whole lot more)?

While I have stated some concerns and provided references, I would not and have not said that pvc is not suitable for any particular application. That is the province of the Engineer responsible for the projects involved. I do believe there are potential issues in the long run from such substances as vinyl chloride and organotins etc. used in the manufacture and constitution of pvc, but that is my opinion based on what I read and understand. As to why I post the observations and knowledge I do on this forum, I want to do so (though I must also like the personal abuse -- no seriously, I think I'm pretty much in it for an occasional "star")! In the coming week those of us in the good ol' US of A will be celebrating our Independence Day. Central to our early government was a stated freedom of speech, that I believe has been reasonably extended by courts to the medium of writing as well. In this spirit I guess others are free to write of me as they wish.
 
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The documentation that you posted does not make it clear whether the vinyl chloride contamination is from groundwater or from piping.

For example, in the list of most polluted communities on:


Being familiar with two communities on this list (The Most Polluted Communities
), I am aware that the #1 Crestwood, IL - Crestwood IL has ductile iron piping and also that the #4 Village of Sauk Village has ductile iron piping.

The vinyl chloride contamination in both of these communites is related to groundwater contamination, not from piping.
 
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Did this thread get hijacked or what?
 
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