Plumbing is meant to last a long time. Traditional metal plumbing products – brass, copper, galvanized steel – all offer decades of service life. Once installed, these materials can deliver trouble-free operation for 70-100 years. More recently, plumbing manufacturers have turned to <plastic plumbing products to address cost and performance issues in traditional metal plumbing. But what should the consumer know about plastic plumbing products, and is it safe to install in your home?
Three most common kinds of plastic plumbing products
Before we launch here, one kind of plastic plumbing product deserves a special mention. Polybutylene plumbing (PB) is a plastic that was used commonly in the 1970s. It is flexible, freeze-resistant and inexpensive – until it breaks. (Then it can get very expensive.)
There’s no nice way to say this: it’s junk. Dangerous and unreliable junk.
If you have it in your home, make plans to retire it sooner rather than later. The original PB products are no longer sold, but plenty of PB pipe remains in service. Currently, there is no known way for homeowners to recover the cost of replacement, and your insurance company likely will not cover damage caused by its failure. Homes with PB plumbing are likely to be worth less on the market than homes without it. In other words, replacing PB plumbing will be a very good investment.
On to the better stuff…
Polyvinyl chloride (PVC) pipe is a rigid, white plastic pipe. People think of it as “new”, but it was actually discovered in 1872. The original formulation was very brittle, and it wasn’t until 1926 that chemists discovered additives that would correct this characteristic.
You can use PVC for both potable and drain/waste/vent applications. It has an expected lifespan of 100 years. PVC is also durable and inexpensive, which makes it a natural choice for new installations and plumbing repairs. PVC pipe doesn’t use the same sizing system that copper tubing uses. If you’re using PVC to replace copper, you need to be aware of this when selecting the appropriate materials and fittings for your projects.
Metal piping relies on solder and fittings to create joints and turns or bends. PVC is rigid, like metal, so it also requires joints to connect pipes or change directions. Unlike metal pipes, PVC uses special cements to join pipes and fittings together. The cement softens the plastic, then hardens it again to create a solid, leak-proof connection.
PVC isn’t recommended for hot water applications that exceed 140°F. That’s hotter than most “default” water heater settings, but your water heater is fully capable of exceeding this temperature. (It’s not recommended. Most codes require special fittings if your water heater normally exceeds 140°F and you can be scalded in a second or two at this temperature.) If your control thermostat gets bumped or creeps around from vibrations, hotter water is going to have a bad impact on PVC plumbing. PVC is also very susceptible to UV damage, and it will freeze. Having said that, PVC is a good choice for cold water systems, vents and drains.
CPVC is PVC’s suaver and more attractive brother. Chlorinated polyvinyl chloride (CPVC) is every good thing that PVC is and a little more. Unlike PVC, it can handle hotter temperatures – up to 200°F. It’s more flexible than PVC, more colorful than PVC and stronger than PVC. It still freezes, though. In addition, some codes place height limitations on PVC and CPVC applications.
CPVC is available in both Nominal Pipe Size (NPS) and copper tubing size (CTS) standards. It does not use the same cement that PVC uses. CPVC is also good for both potable and drain/waste/vent applications, and it can handle hotter water.
Most CPVC products are also vulnerable to UV light. UV light is used in the manufacture of PVC and CPVC, so it can also “undo” PVC and CPVC materials. Direct exposure to sunlight can eventually cause the materials to break down.
Now for the bad part – CPVC is a lot more expensive than PVC. (Five to six times more expensive, to be exact.) Despite the increased expense, CPVC is recommended for hot water systems and some relatively low-temperature exhaust applications.
Some homeowners prefer plastic piping because it is quieter than traditional metal plumbing. You’ll still hear some noises, but you’re not likely to hear the same kind of banging and knocking that you can get from metal plumbing products. It’s not good to mix PVC and CPVC in one run, largely because the cements for each material differ. The performance characteristics also differ; it’s best to stick with one type or the other.
PEX is a soft, flexible plastic pipe. The PEX designation stands for cross-linked polyethylene. This product – which is about 50 years old – can be used for plumbing, heating and cooling. When used in plumbing, it can withstand temperatures to 180°F.
You may already have some PEX in your home. It’s often used to connect water supplies to sinks, toilets and appliances.
When used in plumbing, PEX does have some distinct advantages. Because it’s flexible, it can be used in places where traditional materials could prove problematic. It’s a lower-cost option in many cases. It also resists bursting and freezing. It doesn’t require joints the same way that rigid systems do, so it’s easier to install. PEX is also very quiet compared to rigid pipe. (No “water hammer” from appliance valves.) You can join PEX lines with tools and fittings, as opposed to soldering or cementing pieces together.
PEX plumbing often provides options for remodeling and addition construction, where it may be difficult to add rigid plumbing.
PEX applications can be used in low-rise buildings (under 3 stories), but it’s only used on the clean side of a plumbing system. You’ll still need to use PVC or traditional drain materials on the “dirty” side of your system. Certain specialty PEX formulations can also be used in heating and cooling applications.
Plastic plumbing continues to evolve, and as a homeowner, you’ll likely be seeing more plastic plumbing as time goes on. Using the correct products for your plumbing applications will go a long way to ensuring that you have good results.
If you’d like more information about plastic plumbing products, or are thinking about replacing your traditional plumbing with a plastic alternative, please contact us at Boston Standard Company at (617) 288-2911 for a consultation.
Photo Credit: mel0808johnson, via Flickr