Thread: External DWV need UV protection?

Older home (60+ yeard old) has DWV pipe run on the exterior of the home. Does this need to be UV protected or is this O.K.? See attached photo.

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FWIW, The Plastic Pipe And Fittings Association says:

Can PVC pipe be exposed to the sun?

PVC does not readily degrade when exposed to sunlight (ultraviolet radiation) due to natural UV inhibitors present in the material. Short-term exposure to sunlight, such as during construction, is typically not a problem for PVC pipe. PVC piping may be used in outdoor applications when the piping system is painted with a light-colored water based acrylic or latex paint that is chemically compatible with PVC. When painted, the effects of UV exposure are significantly reduced.

<http://www.ppfahome.org/pvc/faqpvc.html>

That said, I've never actually seen PVC pipe degraded by UV, nor have I talked to anyone who has.

Originally Posted by Michael Thomas

That said, I've never actually seen PVC pipe degraded by UV, nor have I talked to anyone who has.

It degrades nicely in the Florida Sun. Turns brown or gets darker, becomes very brittle, and is easily cracked.

Pvc sched 40 DWV pipe has been used outside as a vent pipe for years and I have never seen it deteriorate as others have mentioned but i live in upstate NY. PVC is also used for furnace venting on high eff. furnaces and ran outside with the same results of nothing happening. It might be right that the pipe needs to be painted or sealed but I have only seen the pvc painted to make it blend into the roof color and even then after a few years the paint chips off and looks like ship. I know I should right it up, but it is so common that even if I do write it up I will be the only one doing so and every contractor and Code inspector will laugh it off and say I have rocks in my head. That being said it is your call depending on your area.

PVC DWV pipes do not degrade much at all "when installed in a protective chase which is also within the insulated thermal envelope of the home" *AS REQUIRED*.

Yes, PVC will deteriorate with UV, and, yes, latex paint (not oil base) may be used to "protect it" from UV, but, it is still required to be in a chase (protection from damage) and within the thermal envelope of the house (protection from freezing).

Originally Posted by Michael Thomas

Can PVC pipe be exposed to the sun?

PVC does not readily degrade when exposed to sunlight (ultraviolet radiation) due to natural UV inhibitors present in the material. Short-term exposure to sunlight, such as during construction, is typically not a problem for PVC pipe. PVC piping may be used in outdoor applications when the piping system is painted with a light-colored water based acrylic or latex paint that is chemically compatible with PVC. When painted, the effects of UV exposure are significantly reduced.

What I find interesting is the apparent contradiction in their statements. They say PVC does not readily degrade when exposed to sunlight, but then go on to say it should be painted if used in an outdoor application. Also, they say to use a light colored paint, whereas it's normally painted with a black to match the roof. Wondering if the color really matters or not. Thoughts?

I found this interesting article online regarding a study that was done. They basically mirror the comments by the pipe fitters that it helps to protect the PVC by painting with an opaque material.

Uni-Bell PVC Pipe Association

It does not just degrade in sunlight . It degrades in hot attics as well. Just a month ago I inspected and attic with a concrete tile roof. Due to penetrations they connected vents together running horizontally across the attic. One had such a large bow in it because it was not supported in the center and had filled with water. I barely tapped it with my foot stepping over it and first one end snapped at the y heading out the roof and when it fell the far end snapped off as well. Oil based products dry out over time and get brittle and lose there flexibility.

Cut a piece of vent pipe into 2 one foot lengths. Keep one in your garage and throw the other into the back yard for 6 months. After that time bring them both to your patio and hit each with a hammer. The one that has been in the back yard will shatter and the one from the garage the hammer will still bounce off

Originally Posted by Scott Dana

What I find interesting is the apparent contradiction in their statements. They say PVC does not readily degrade when exposed to sunlight,

That means it is okay to expose it to sunlight during storage, transport, warehousing, and site storage without having to cover it or otherwise protect it from sunlight.

but then go on to say it should be painted if used in an outdoor application.

Because long term expose to sunlight (UV) is not good for it, UV will deteriorate the PVC.

Also, they say to use a light colored paint, whereas it's normally painted with a black to match the roof. Wondering if the color really matters or not. Thoughts?

That part is answered in your other link.

Originally Posted by Scott Dana

Uni-Bell PVC Pipe Association

"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."

Darker colors will absorb heat more, causing the PVC to heat up.

In one of my prior careers, I was the Quality Mgr at a PVC pipe extrusion plant. In that role, I was involved with UL testing, NSF testing, R&D experimentation and daily production, including storage. We did include UV inhibitors in our formulations. When the inhibitors were missing or insufficient, the Texas sun would turn the pipe dark brown within 24 hours. Pipe in our inventory yard for more than roughly 6 months would begin to brown and could not be sold. This discoloration occurred on joints that were on the outside of the packs and the exposed ends of interior joints. It was clearly the UV, not the heat that caused the discoloration.

We had ongoing R&D efforts to attack the brittleness issues and determined that heat was a major contributor to this characteristic. One practical example again occurred in the pipe yard where the joints interior to the packs became brittle at a more rapid rate than the exterior joints. Developing an effective formulation without this characteristic would have been a market breakthrough. We did it and sold a lot of it.

From this experience, we recommended any opaque water based paint for UV exposed residential locations.

Darrel Hood
DILIGENT PROPERTY SERVICES

Great info Darrel and everyone else, thanks.

Which all leads to another problem with using those rubber flashings instead of the lead flashings when plumbing vents terminate through roofs: The rubber flashings expose *a lot* (comparatively speaking) of PVC to sunlight while the lead flashings expose *very little* PVC to sunlight.

Originally Posted by Jerry Peck

Which all leads to another problem with using those rubber flashings instead of the lead flashings when plumbing vents terminate through roofs: The rubber flashings expose *a lot* (comparatively speaking) of PVC to sunlight while the lead flashings expose *very little* PVC to sunlight.

It's true that the rubber flashings expose a lot of PVC to sunlight, but I've never seen a squirrel eat a rubber flashing. I've seen 'em eat lead right down to the shingles. The rubber flashings do degrade after 7-10 years in our climate, although I've never seen PVC vents degrade above a roof.
Ya pay your money and ya take your chances.

Originally Posted by Kevin Barre

but I've never seen a squirrel eat a rubber flashing. I've seen 'em eat lead right down to the shingles.

What is a whole lot cheaper than replacing those rubber ones every 6-7 years would be to install a lead one and wrap it with hardware cloth wire mat. Keeps those squirrels from getting to the lead ones.

I would be more concerned about the cast iron above pushing down and splitting out the PVC. The CI is not properly supported to prevent the crushing / cracking of the PVC.

Patrick,

Now that you have brought it back to the original post, you've really done it.

All of the previous discussions have centered around the PVC being exposed to sunlight and UV, which it is not allowed to be blah, blah, blah.

Now for ... a pet peeve of mine ... which I've brought up many times before ... and for which you have opened the door ... (thank you) ... (but the others may not) ...

Anyone out there know where the 'freeze line' is and above that line which *ALL* (yes *ALL*) plumbing outside the thermal envelope of the house is supposed to be insulated?

I've posted it many times before. Yes, this is a test. WC Jerry keep quiet.

Originally Posted by Jerry Peck

.

Anyone out there know where the 'freeze line' is and above that line which *ALL* (yes *ALL*) plumbing outside the thermal envelope of the house is supposed to be insulated?

I've posted it many times before. Yes, this is a test. WC Jerry keep quiet.

.
Looking in the Plumbing Appendix it runs approximately from Jacksonville Fl. westward across Tallahassee the Fl. Panhandle extending into Texas.
.

Just because it is white and stamped PVC doesn't make it all the same. Interesting to read all the different rates of UV degradation seen on this thread.

Being a budget sailboat racer for many years, I used PVC pipe as a wisker pole on a 25.5' Hunter. The pole was 9' and stored on the deck in direct sun. I used the pole for over 5 years and it was flexed frequently without cracking or breaking. I also made a bottom brush of 4' sections and threaded fittings, one was a 45 deg. elbow to reach the bottom. The pipe was mfg. by Charlotte Pipe which may have a better than normal UV formula, don't know.

Just my experience with PVC, don't think I have a problem with vents that are not painted.

Vern,
I once owned a Hunter 25.5. It was probably the best all around family boat I have ever had. I wish I still had it and envy you for yours.

Darrel Hood
DILIGENT PROPERTY SERVICES

To a large degree, Vern is right. Although NSF keeps a tight rein on the formulations for each manufacturer, there are allowable ranges in the formulas. Therefore, there can be different performance characteristics for each company's products.

Darrel Hood
DILIGENT PROPERTY SERVICES

Darrel, my son talked me into selling the Hunter about 7yrs ago and gitting a Soverel 33. Went from being able to race single handed and stay in the metal to having to have a crew of 9 and staying at the back of the pack, due to no show fair weather sailors. Everyone wanted to go on the race until the weather wasn't perfect or they were marginaly over served on the Friday night befor the race! Sold the Soverel 2 yrs ago and now have a J24 that I love, can be raced with some hope of winning by 2 and have won single handed. Still a budget racer but don't have PVC spin pole!

Originally Posted by Billy Stephens

.
Looking in the Plumbing Appendix it runs approximately from Jacksonville Fl. westward across Tallahassee the Fl. Panhandle extending into Texas.
.

Yes, a winner.

Billy, the easiest way to remember that line is to think: If the house is above US I-10, *ALL* of the pipes outside the thermal envelope need to be insulated, supply, waste, and vent.

If the house is below I-10 ... no problemo.

I-10 runs approximately along the line given by the cities listed in the Plumbing Appendix.

I pointed this out as Robert, and the original photo, are in SC, which is quite a ways above I-10.

In other words ... Robert should not have been able to see that waste and vent, it should be insulated and then boxed in, whereby the exposure to UV becomes a non-issue.

UV breakdown of PVC pipe is more of an issue at lower latitudes, where the sun's rays are stronger year-round, than farther north. Higher altitudes also receive stronger UV radiation than lower altitudes.

My home, built in 1976, has the original pvc vent pipes through the roof, and they've never been painted. I check them twice each year when I go on the roof to clean the gutters and to inspect the condition of the asphalt shingles and the flashings. After 32 years of exposure, there are no signs of the PVC vent pipes being damaged by UV, and if they were to be damaged it would be an easy fix to cut them off inside the attic and extend a new piece of PVC back through the roof.

It's rare to find it painted up here, but if it is not protected I still write it up. I don't expect folks will heed my advice to paint it, and around here leaving it unprotected probably carrys low risk of it causing problems.

Originally Posted by Jerry Peck

Now for ... a pet peeve of mine ... which I've brought up many times before ... and for which you have opened the door ... (thank you) ... (but the others may not) ...

Anyone out there know where the 'freeze line' is and above that line which *ALL* (yes *ALL*) plumbing outside the thermal envelope of the house is supposed to be insulated?

I've posted it many times before. Yes, this is a test. WC Jerry keep quiet.

All I need to know is that it is far south of the state of New York!

P.S. our footings need to be more than 48 inches below finished grade up here. Most natural lakes and ponds are warm enough to swim only during July & August....

Gotta go out now and rake some leaves, put away the lawnmower, and tune up the snowblower.