Why do they paint 2-inch pool pipes black? (just repaired with 2" white PVC)

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I'm curious why they paint all the white 2-inch PVC pool pump area pipes flat black?
On Friday, I put a new pool pump motor in but forgot to open all the Jandy valves so the pipes overheated, expanded, and blew up in places (a 1.5 HP motor is strong!).
Anyway, my 2 inch outside diameter PVC pipe from Home Depot earlier today now stands off as bright white while the rest of the pipes re painted flat black.
No big deal but I was wondering WHY they paint the PVC pool pipes black and if it's a good enough reason for me to follow suit on my 2-foot section of repair pipes.
The three reasons I can think of don't seem to hold water: - heat retention? (c'mon ... how much heat will black retain over white on a few pipes that are in the open sun?) - sunlight damage? (maybe ... but then why don't they just sell pool pipes that have paint on them already) - asthetics? (c'mon ... can black matter versus white)
Any other reason for the flat black pool pipe paint?
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On Apr 18, 11:03 pm, Brent <beemdoub...@Use-Author-Supplied- Address.invalid> wrote:

Paint is for UV protection of the white PVC (not sunlight resistant). btw, pre-painted PVC would be a PITA to solvent weld
Could you clarify this sentence?

valves so the pipes overheated, expanded, and blew up in places (a 1.5 HP motor is strong!). " <<<<<<<<
What caused what to overheat? Did the system have water in it?
The horsepower of the pump is pretty much meaningless with respect to "blowing up" pipes.
It's the amount of head (pressure) generated that stresses the piping.
A 1.5 hp pump / motor can either deliver high flow / low head or low flow / high head or something in between; depends on the pump design / curve. Most pool pumps would be hard pressed to get anywhere near the allowable maximum pressure for PVC piping.
cheers Bob
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DD_BobK wrote:

A pump running with no flow through heats up the water in it quickly due to the internal friction. The pipe gets warm and softens. The pressure blows it out.
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On Mon, 19 Apr 2010 07:45:13 -0700, Bob F wrote:

That's exactly what happened!
The pump ran but couldn't push any water past the shutoff (the jandy shutoff leaked profusely but not enough).
Then the threads must have softened and the pipes heated up because a post-mortem analysis showed the threaded pipes melted in a V shape (hard to explain) such that they just blew right out of the motor.
When I tried to connect 2" OD PVC to the cut edge of the pipe run, I found that the 2 inches had swelled greatly (almost a sixteenth of an inch or so ... way more than can be sanded).
So I just cut off MORE pipe (no big deal); but I was wondering about the paint.
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On Sun, 18 Apr 2010 23:24:49 -0700 (PDT), DD_BobK wrote:

Hi Bob, To clarify, I'm not really sure if the 220 Volt 1.5 HP motor horsepower mattered but what I saw was a two-inch wide stream of water shooting straight up in the air about fifteen feet!
It was like a rocket ship was taking off when the pipes heated up so much that the threads gave way on the fitting comeing up vertically from the motor impeller on the pressure side of the pump. Kaboom!
Afterward, when I cut the pipe and put new parts in, for a good foot or so, the 2 inch OD white PVC pipe was way larger than 2 inches on the outside such that no fitting would fit.
I was very confused because otherwise the very thick (shedule 40 at least!) PVC pipe didn't seem to be any standard. Finally I realized the heat expanded the pipe so much that it was no longer 2 inches in outside diameter.
I simply cut away all the bad pipe but had to go into my spares box and accidentally pulled out a black ABS fitting and glued that in. Unfortunately, I now know that the black ABS pipe isn't pressure rated so it's going to be a weak link (where were you when I needed you ... :-)
I'm not really sure WHY a pump that has plenty of water with nowhere to go heats things up ...
Maybe the water bashing back and forth at high speed, going around in circle after circle after circle after circle heats it up because even the basket on the inboard side of the pool pump was melted and had to be replaced.
SOMETHING about the water having nowhere to go made it get hot as hell there until the system blew up!
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On Tue, 20 Apr 2010 02:07:11 +0000 (UTC), Brent

Either you just invented a new way to heat water, or the FBI will come to your place to investigate the bomb you made and you'll be listed as a terrorist.
You should get help for your drinking problem...... I mean, how did you turn on the motor and not open the valves? It might be your medications too.
They painted them black because they did not paint them red, orange, green, yellow, blue, brown or purple. However, the person that said it's for UV protection, and I'd repaint them any color you like. At the same time, flat black will absorb more sunlight and make the water warmer. In your case, thats the last thing you need to do.
If that's a 2inch OD, then it's 1 1/2" pvc. Pipe is always measured by the ID size, with the exception of some of the soft copper tubing, which is one of the most confusing things a plummmmmahhhhhh has to deal with.
The black ABS fitting may not hold up, I'd replace it.
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On Mon, 19 Apr 2010 06:03:41 +0000 (UTC), Brent

So they won't explode. Haven't you learned that by now?

Oh, never mind.

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The pipes are probably not U.V. protected, so they'd deteriorate from the sun without a covering over them
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Brent wrote:

The paint is to protect the PVC from the UV of the sun. White paint, (or green or red or blue) would work just as well.
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On 4/19/2010 8:51 AM, Steve Barker wrote:

Black pigments are the most effective UV absorbers.
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On Mon, 19 Apr 2010 09:14:44 -0400, George wrote:

I wonder why they don't just sell black PVC 2" OD pipe then???
Even at Leslies' Pool Supply, they're white.
Everyone seems to just paint them.
It's cheap and easy; but I was just wondering why we don't just start out with UV-resistant PVC pipe???
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Brent wrote:

Maybe they don't want to confuse PVC with ABS?
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wrote:

I wondered about this myself. Is the OP sure the original pipes weren't ABS? That is what they use for solar panel connections. On the other hand I have never seen a pool with painted PVC pipe unless it was painted when they painted the house. That is in Florida where we actually have some sun.
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On Mon, 19 Apr 2010 16:59:17 -0400, snipped-for-privacy@aol.com wrote:

We have LOTS of sun here. All day sun.
I'm not sure if it's ABS or PVC for all the pipes, but the pipes I bought at Home Deport say they are PVC.
What made me wonder about the black versus white was I needed a fitting and I grabbed one that was black through and through. I mixed it in with the white fittings and then painted the white ones.
I wonder (based on the ABS question) if that one black fitting was ABS while the rest (the white ones) are PVC?
That makes me wonder: What's the difference from a practical standpoint for outdoor 12-hours-a-day-in-the-sun 2-inch OD pool water pipes between black ABS and white-painted-black PVC pipe?
Note: Leslies pool supply sold only the white PVC so maybe I should have asked the teenager behind the counter but I didn't think of it when I was there.
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On Tue, 20 Apr 2010 00:00:31 +0000 (UTC), Brent

If you cut the end and it is black in the middle, it is ABS. That is what the solar contractors use. Pool contractors use PVC for the regular pool plumbing.
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Painting black reduces the absorption of UVA, B, and C so that the pipe lasts a little longer.
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On Mon, 19 Apr 2010 18:30:23 -0700, "Steve B"

I live in South Florida where water doesn't freeze. There are folks around here with well pipes, water softeners pressure tanks etc, that have been in the sun for 30 years without breaking so I do think the UV thing may be overstated a bit. Sure if you back over one with your car it will break but it isn't just going to spontaneously shatter.
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On Apr 19, 10:24 pm, snipped-for-privacy@aol.com wrote:

I took out some PVC pipe that had been exposed to the sun for about 7 years. It was still doing its job but it was brittle as heck.
Jimmie
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On Mon, 19 Apr 2010 21:18:37 -0400, snipped-for-privacy@aol.com wrote:

Given that, ALL the pipes I cut were white on the inside (with purple glue at the seams).
A single 4-inch-long sleev-like fitting I grabbed out of the miriad of various elbow-like fittings I bought at the hardware store was black all the way through as I had to cut it to fit.
So, given that black is ABS and white is PVC, my pool plumbing is currently 99% (white) PVC with that single fitting of (black) ABS that I used without knowing the difference.
Now that I realize I've mixed ABS with PVC ... I wonder ... does it matter that I have ABS accidentally mixed in with mostly PVC (painted black)?
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On Tue, 20 Apr 2010 00:00:31 +0000 (UTC), Brent wrote:

"The Effects of Ultraviolet Radiation on PVC Pipe" http://www.uni-bell.org/pubs/uni-tr-5.pdf
Summarized by the PVC Pipe Association here: http://www.uni-bell.org/faq.html
Further summarized by yours truly below: Q: What effect does ultraviolet exposure have on PVC pipe? A: Not much but enough to warrant a thin coat of opaque paint!
Modulus of Elasticity = unchanged after two years of sun Tensile Strength = unchanged after two years of sun Impact Strength = reduced drastically (by 75%) after two years of sun Structural Integrity = unchanged after two years of sun Pressure Capacity unchanged after two years of sun
The loss of impact strength stopped deteriorating as soon as the pipes were protected by the sun so it's directly related to the UV radiation.
Luckily, 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 or burial.
Why black? What's more opaque than black? Electrical PVC outdoor pipe is gray. Go figure.
PS: I heard some paint won't stick to PVC so maybe you need special PVC paint?
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