PVC pipe

Description

PVC pipes are hollow cylinders of Polyvinyl chloride in prescribed sizes. They were invented in the mid-20th century to replace metal plumbing pipes, and are still primarily used for DWV applications (Drain-Waste-Vent).

PVC pipes are produced by multiple different manufacturers and are widely available in the plumbing sections of hardware stores. Thanks to their accessibility and affordability, PVC pipes became a common fixture in DIY projects and the Maker Movement. As a result, more aesthetic 'furniture grade' PVC pipe can now be purchased. Charlotte Pipe and JM Eagle are two common brands for plumbing-grade PVC pipe, while furniture-grade PVC pipe produced by Formufit can be bought in major stores and online. However, Formufit is $1.40 per inch, while a big-box hardware store Charlotte Pipe is $0.56 per inch (as of June 2020).

CPVC pipes and uPVC pipes are distinct from PVC pipes. The C of CPVC stands for chlorinated, and the u of uPVC for unplasticized. Both are less common and more difficult to acquire in small quantities.

Synonyms and Related Terms

Plastic pipes, plumbing pipes

Applications

PVC pipe is commonly used for simple construction projects, as it is readily available and cheap. Additionally, PVC pipe projects can be easily dismantled for relocation or reuse of parts.

Within conservation, PVC pipes are most frequently used as skeletons for large lightweight collapsible structures like lighting tents for photography, humidity chambers and fume chambers. Their structural use with more permanent installations--for display or storage--is tempered by their potential to offgas.

Personal Risk

Hazards listed in the Charlotte Pipe SDS for plumbing-grade PVC pipe

Inhalation:	Melted product is flammable and produces intense heat and dense smoke during burning. Irritating gases and fumes may be given off during burning or thermal decomposition.
Skin contact:	Gases and fumes evolved during thermal processing or decomposition can cause skin irritation.
Eye contact:	Dust can cause eye irritation. Gases and fumes evolved during thermal processing or decomposition can cause eye irritation.

Regulatory Information from the Charlotte Pipe SDS: Airborne unbound particles of titanium dioxide of respirable size are listed as being carcinogenic per California Proposition 65.

Toxicological Information from the JM Eagle SDS: PVC resin contains minor amounts (<1 ppm, 0.0001%) of residual vinyl chloride monomer. Vinyl chloride is listed as a carcinogen under California Proposition 65.

No further information on toxicology or regulation is available in the Formufit SDS.

Environmental Risk

Like all plastics, PVC is a petrochemical product with a high energy production cost and a long lifespan with no biodegradability. Plastic particles are a pollutant that contaminate the soil and water supply.

PVC (resin code 3) is considered a contaminant in mixed-source recycling because its degradation products are chlorine and hydrochloric acid, which disrupt other polymers. As it can only be recycled in single-source dedicated facilities, it has a low recycling potential.

Collection Risk

The major collection risks of PVC piping are off-gassed Chlorine compounds and Plasticizer migration. As such, conservators tend to advocate against using PVC in enclosed containers with objects or directly touching objects.

The following are the hazardous decomposition products listed on the Charlotte Pipe SDS for PVC pipes: Hydrogen chloride, Carbon monoxide, Carbon dioxide, Phosgene, small amounts of Benzene, aromatic hydrocarbons and aliphatic hydrocarbons. Chlorides are especially dangerous around copper objects, as chloride can precipitate Bronze disease. Chlorine is a strong oxidizing agent and poses a substantial risk to collections, especially Organic items.

While PVC pipes are classified as 'rigid PVC', they are not free of plasticizers; only uPVC is labelled as unplasticized. The most common plasticizer in PVC are phthalates, so they are likely to be present to some concentration in PVC pipes.

Formufit describes their furniture-grade PVC as superior to plumbing-grade PVC as it is "completely non-toxic and contain no heavy metals (such as lead), noxious dioxins, phalates [sic] or other dangerous plasticizers." Their own SDS describes their pipes as containing minor amounts of "PVC Additives (for UV Protection and Impact Resistance)" but no further clarification, as it is a proprietary product.

Similarly, the industrial manufacturers do not specify all the additives that are in their PVC pipes. Charlotte Pipe records that Titanium dioxide is used to color the pipe white. JM Eagle lists their hazardous additives as "pigments, base metal, catalyst, alloys, vehicle, metallic coatings, solvents, filler metal (+ coating or core flux) and other", all at a "non-applicable" percentage of the total weight.

Working Properties

PVC pipe can be cut with either a manual or powered saw, and there are also inexpensive pipe cutters you can buy. As with all cylinders, ensure that the pipe is clamped down before sawing through it, especially with a power tool.

The edge may be rough or jagged after cutting, so sanding the edge might be preferable if it is uncomfortable to work with or visible in the end product. Small flakes of PVC will be produced and spread by cutting and sanding, so plan ahead with a dust mask and a cleanable workspace.

As a thermoplastic, PVC can also be manipulated with heat, but only attempt with caution as PVC fires are extremely dangerous. Additionally, PVC resin contains trace amounts of hazardous vinyl chloride monomers, a carcinogen. Take appropriate safety precautions when deforming PVC.

Forms and Sizes

Plumbing-grade PVC pipe is sold by the foot at hardware stores, commonly cut from 10" stock. Furniture-grade PVC pipe from Formufit is sold on their website in a pack of two 5-foot lengths.

Sizes

PVC pipe has two important size distinctions: the Nominal Pipe Size (NPS) and the Schedule.

The schedule refers to the thickness of its walls: most pipes sold for consumer purposes are Schedule 40, but Schedule 80 can also be found. The Schedule 40 pipe has thinner walls than the Schedule 80 pipe, but the same exterior diameter.

The Nominal Pipe Size is taken from the average interior diameter of the pipe. Thus, a 1" PVC pipe actually has an exterior diameter of 1.315", but an interior diameter in Schedule 40 pipe of 1.049".

Standardized Dimensions of PVC Pipes

Nominal Pipe Size (in.)	Outside Diameter (in.)	Inside Diameter: Schedule 40 (in.)	Inside Diameter: Schedule 80 (in.)
1/2	0.840	0.622	0.546
3/4	1.050	0.824	0.742
1	1.315	1.049	0.957
1 1/4	1.660	1.380	1.278
1 1/2	1.900	1.610	1.500
2	2.375	2.067	1.939
2 1/2	2.875	2.469	2.323
3	3.500	3.068	2.900
4	4.500	4.026	3.826
5	5.563	5.047	4.813
6	6.625	6.065	5.761
8	8.625	7.981	7.625
10	10.750	10.020	9.564
12	12.750	11.938	11.376
14	14.000	13.124	12.500
16	16.000	15.000	14.314

Formufit sells furniture-grade Schedule 40 pipes in ½, ¾, 1, 1 ¼, 1 ½, and 2 inch nominal sizes.

Appearance

Industrial PVC pipe is white and matte, with printed manufacturers information on the side. The printed information can be removed with a solvent or sandpaper if desired. Usually Schedule 80 pipe is dark grey, as opposed to white. UV degradation will yellow white PVC pipe.

Furniture-grade PVC is shiny and sold without information printed on the side. The color options are usually white, black, grey, red, orange, yellow, green, blue, purple, pink, and clear.

Resources and Citations

• Plumbing-grade PVC pipes: Charlotte Pipe SDS, JM Eagle SDS
• Furniture-grade PVC pipes: Formufit SDS
• Plastic Pipework on Wikipedia
• PVC Pipes on Wikipedia
• Kate Aguirre, contributed information, MWG group, 2020.