UV degradation of PVC piping

[DLSDO]

tillys26,

Also, I see from your posts that your pool was started on October 20, so it has been over a month. Is your PB planning on painting the white PVC plumbing? The ultraviolet (UV) from the sun willl eventually cause the PVC to degrade.
Titanium

Titanium,
What should the white PVC plumbing be painted with? I did not know the PVC would degrade. About how long does it take till damage is done?

Thanks,

 

[DLSDO]

Titanium,
I think we posted at about the same time. See my question just above your last post. What do you think?

Thanks,

 

[Titanium]

DLSDO,

I have no experience - yet - with painting PVC piping, but I would imagine the Rustoleum spray cans that are compatible with plastic should work fine.

I think it takes on the order of several years for the ultraviolet rays to appreciably degrade PVC piping, although the links below suggest that PVC piping will be structurally sound after UV radiation, but it will probably not look very good.

Have you every wondered why PVC piping is white, whereas PVC electrical conduit is gray? One of the differences, other than UL listing, is that the gray PVC is rated to be installed outdoors in the sunlight.



http://www.uni-bell.org/faq.html

Q: What effect does ultraviolet exposure have on PVC pipe?

A: In order to accurately quantify the effects of UV radiation on PVC pipe, Uni-Bell members conducted a two-year study in the late 1970s at various outdoor locations in the United States and Canada. In this study, PVC pipe samples were placed on horizontal exposure racks and placed so that they received continual exposure to the sun. At various points throughout the study, tests to evaluate mechanical properties were performed on the portion of the pipes that received the maximum UV exposure.

The results of the study (published as UNI-TR-5, "The Effects of Ultraviolet Aging on PVC Pipe") indicate a gradual decline in the pipe's impact strength. The lowest impact strength recorded after two years of exposure was 158 ft-lbf, or 75% of the original ASTM value. Even this reduced value exceeds those of most alternative sewer pipe products. These results indicate that no unusual handling problems should be expected from PVC pipe even after long-term exposure to sunlight.

The study results also show that Modulus of Elasticity and Tensile Strength were virtually unaffected. The fact that these properties are unaffected signifies that structural integrity and pressure capacity remain unchanged. UV degradation does not continue after installation when exposure to UV radiation is terminated.

The presence of an opaque surface between the sun and the pipe prevents UV degradation, since UV radiation will not penetrate thin shields such as paint coatings or wrappings. Burial provides complete protection.

When exposure in excess of two years of direct sunlight is unavoidable, PVC pipe should be covered with an opaque material while permitting adequate air circulation around the pipe. This prevents excessive heat accumulation.

http://www.uni-bell.org/pubs/uni-tr-5.pdf

Because degradation is dependent upon solar radiation, all UV degradation ceases when exposure to UV radiation is terminated. Thus, buried pipelines will not continue to degrade. In fact, any opaque shield, no matter how thin, will effectively prevent UV degradation. The most common method used to protect above ground PVC pipe from the sun is painting with an acrylic or latex (water-based) paint. Preparation of the surface to be painted is very important. The pipe should be cleaned to remove moisture, dirt, and oil, and then wiped with a clean, dry cloth. Petroleum-based paints should not be used since the presence of petroleum will prevent proper bonding of paint to pipe. In addition, PVC pipes intended for outdoor use (e.g. PVC above-ground irrigation pipe) may be formulated with special additives, similar to those used in PVC house siding, that effectively prevent any significant UV degradation.

 

[DLSDO]

Titanium,
WOW!! Thanks. Now thats some answer. I am thinking about spraying mine black. Do you think the color matters?

Tilly,
Sorry for the off topic thread hijack!

Thanks,

 

[Titanium]

DLSDO,

When I purchased our 23 year old house and pool last year, I found that our pool piping had been painted black. Since I have had to do some minor piping work to install¹ my new Ikeric/Hayward pump/motor, I have some areas that are white now. I will probably re-paint all of the piping beige to match the exterior of the house since my equipment pad is right near the house.

I also apologize for the thread hijack. Perhaps one of the moderators would be so kind as to move these posts into a new thread titled "UV degradation of PVC piping"? Or maybe some other catchier title.

Titanium

¹ The Hayward Tri-Star pump/motor had internal threads which matched the old Hayward Super II pump exactly in height and position. But the new Hayward Tri-Star pump/motor also had external threads and unions, and using these unions required some cutting and gluing of the existing piping.

 

[JohnT]

Plain old latex works well. Just make sure to clean the pipe well. It's usually dirty as heck when you get it. When I relocated my equipment pad, I reused some pipe with fittings in it. I noticed that there were more chips on the inside of the used pipe than the new when I cut it, and it had only been in the sun for two years. Might have just been a different manufacturer.

 

[Titanium]

JohnT,

Thank you very much for moving this to a new thread.

I have really enjoyed reading some of your posts in the past. I take it that you have an electrical background? Your discussions about bonding, grounding, and "stray voltage" around swimming pools have been very well written and technically accurate. Have you seen the "stray voltage" topics at www.mikeholt.com ?

Thanks again!

Titanium

 

[JohnT]

JohnT,

Thank you very much for moving this to a new thread.

I have really enjoyed reading some of your posts in the past. I take it that you have an electrical background? Your discussions about bonding, grounding, and "stray voltage" around swimming pools have been very well written and technically accurate. Have you seen the "stray voltage" topics at www.mikeholt.com ?

Thanks again!

Titanium

I'm not sure who moved it, but it wasn't me. I'm an electrical engineer with a friend who is an electrician. I've spent a bunch of time with him trying to help him teach the city inspectors what the NEC really means so he can get paid. That means I have to learn it first :? , and it is a real treat. Mike Holt's forum is a great resource, and it's usually the first place I turn for code information.

 

[duraleigh]

As usual, I'm late to the party, but I question the necessity to paint PVC piping. I have reused PVC that has been exposed to UV for at least three years and can determine no degradation.....except for a little chalkiness on the surface. Certainly it looks nicer to paint it (normally) and it cannot hurt but I have never been of the opinion that painting it is a necessity.

None of my pool plumbing is exposed to direct UV but some of my irrigation is....chime in if you think the painting is necessary.

 

[Titanium]

duraleigh,

Certainly it looks nicer to paint it (normally) and it cannot hurt but I have never been of the opinion that painting it is a necessity.

It appears that you are correct that painting the pool piping is not necessary. I had always thought that PVC plumbing needed to painted. However, the information that I read on the Uni-Bell website has changed my mind.

But I'm still going to repaint my piping next spring to match the house.

Titanium

 

[Titanium]

John T,

The Mike Holt website is a great place to learn about the National Electrical Code (NEC). I spent my entire career designing and troubleshooting electrical installations in industrial facilities, which of course need to be installed per the NEC. Usually we were designing our electrical installation much better than the NEC minimum requirements since our facilities had to be reliable, maintainable, efficient, etc and all the NEC is concerned about is fire and safety.

I was continually learning new things in the NEC and never was able to consider myself an expert in the NEC. And just to make things interesting, the NEC is modified and changed every three years.

What fun.

On a side note, have you had a chance to play around with pool automation systems yet? Or perhaps thought about using a PLC to create a homebrew DIY version?

Titanium

 

[JohnT]

On a side note, have you had a chance to play around with pool automation systems yet? Or perhaps thought about using a PLC to create a homebrew DIY version?

Titanium

I've been playing around with a timer and a remote temperature indicator. I want it to eventually give me air, pool, solar panel surface and solar outlet water temperatures so I can set it to control pump run time and solar operation. Been busy this year with major plumbing rework, so I haven't made any progress.

 

[cliff_s]

The White PVC is meant for interior use. The Grey is used for electrical conduit and not
liquids, although it does contain a UV inhibitor. The White PVC has no UV inhibitor in the material
so it will deteriorate after a while, this is why it is painted(it makes no difference what color as the
paint itself blocks the UV).

I, too have been looking for some wireless temp senders for my pool temp, spa temp and etc.
I have tried the Oregon Scientific ones but they only lasted a couple of months. They seem very poorly
made and the remotes all leaked.

Cliff s

 

[duraleigh]

In order to accurately quantify the effects of UV radiation on PVC pipe, Uni-Bell members conducted a two-year study in the late 1970s at various outdoor locations in the United States and Canada. In this study, PVC pipe samples were placed on horizontal exposure racks and placed so that they received continual exposure to the sun. At various points throughout the study, tests to evaluate mechanical properties were performed on the portion of the pipes that received the maximum UV exposure.
The results of the study (published as UNI-TR-5, "The Effects of Ultraviolet Aging on PVC Pipe") indicate a gradual decline in the pipe's IMPACT strength. The lowest impact strength recorded after two years of exposure was 158 ft-lbf, or 75% of the original ASTM value. Even this reduced value exceeds those of most alternative sewer pipe products. These results indicate that no unusual handling problems should be expected from PVC pipe even after long-term exposure to sunlight.

The study results also show that Modulus of Elasticity and Tensile Strength were virtually unaffected. The fact that these properties are unaffected signifies that structural integrity and pressure capacity remain unchanged. UV degradation does not continue after installation when exposure to UV radiation is terminated.

The presence of an opaque surface between the sun and the pipe prevents UV degradation, since UV radiation will not penetrate thin shields such as paint coatings or wrappings. Burial provides complete protection.

When exposure in excess of two years of direct sunlight is unavoidable, PVC pipe should be covered with an opaque material while permitting adequate air circulation around the pipe. This prevents excessive heat accumulation.

Emphasis on the word "impact" is mine. Interesting study.

 

[RocKKer]

In my county the PVC has to be painted because the code requires it. My friend's pre-code non-painted pool plumbing PVC has yellowed substantially, but after 15 - 20 years it still is holding up just fine.

I used Krylon's Fusion, which Krylon says is specific for plastic. I used gloss black for my solar on the roof and at the equipment pad, because I have heard the gloss will last longer then flat and for the solar pipes running up the wall I painted with matching house paint.

For me the paint hides all the "extra" blue PVC cement.

 

[flintstone]

If practical experience is any indicator of the effectiveness of PVC to withstand impact, then I am very supportive of doing anything I can to protect my pipes. Last summer, while caring for my father-in law's lawn, I knocked into a manifold of pipes positioned above ground that had been exposed to sunlight and they split. Water went everywhere. I have also stepped on some PVC pipe that was stored outside in my back yard and it shattered. It looked like crushed egg shells. Pipe stored in my garage did not suffer the same degradation. So in the words of the Rolling Stones...
I wanna see it painted, painted black
Black as night, black as coal
I wanna see the sun blotted out from the sky
I wanna see it painted, painted, painted, painted black
Yeah!