How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
What is the average life expectancy of copper pipe?
Friday, July 27, 2018
Copper water supply pipe should last 50 to 80 years, with an average of 70 years. Unfortunately, “aggressive” acidic water or soil can cause pitting-type corrosion and shorten the lifespan to 20 years or less. Also, other combinations of alkaline ph, hardness, and contaminants can activate pitting, which is essentially the dissolving of copper ions into the water flow at spots on the pipe wall. In extreme cases, the water is tinted a green-blue from the copper leaching.
Water with a neutral ph (7.0) is ideal for the long life of copper piping. Our local water company, Gainesville Regional Utilities (GRU) rated the ph of water leaving the treatment plant is 8.6 (slightly alkaline, due to the dissolved karst in our aquifer) in a recent annual report. But when we test the water at the kitchen faucet during home inspections, the average ph is closer to 7.0, possibly changed by the distribution pipes.
Copper was the standard choice for water pipe in North Florida from the early 1970s to about 2000, when CPVC (a cream-color plastic) pipe became more popular, largely due to its resistance to pin-hole leaks caused by pitting, the less-expensive material cost, and somewhat easier installation.
The lifespan of the copper pipe is also affected by the grade of pipe installed. There are three grades:
- Type K - 0.049 inch thick wall, recognizable by green lettering on pipe
- Type L - 0.040 inch thick wall, recognizable by blue lettering on pipe
- Type M - 0.026 inch thick wall, recognizable by red lettering on pipe
Both L and M are commonly used in residential construction. Obviously, Type L pipe’s thicker wall means a longer lifespan, but Type M is the predominant one installed. Patina formation on the surface may make it difficult for you to identify the lettering color on older pipe.
In our area, we primarily find leakage under the floor slab. Copper pipe should be set in clean fill sand under the floor slab when the house is constructed, because the acidity of regular black soil will accelerate the pitting. “If the pipe was not bedded properly in sand, or cheap copper pipe was used, under-slab leaks can start as early as 10-years after the house was built,” according to James Freeman, of J.W. Freeman Plumbing.
Under-slab pipe failure can be found with an infrared camera because the leaking water cools the area of the leak, but the infrared photo below shows an unusual image of a pipe leak of a hot water pipe.
Another cause of copper pipe failure is shown below, in the compartment under a master bathroom spa tub. “The green area on the pipe is from the acidic flux that was used to make the solder joints not being wiped off after the joint was made,” says James. “And the white crud buildup is a very small active leak that leaves water-mineral deposits behind as the water leaking out evaporates.” You can also see more of it in a small pile on the floor below the leak.
Here’s a graph that compares the life expectancy of copper to other types of pipe used in residential plumbing.
Go to our blog post What is the average lifespan of the parts of a house? for rating of other house components. To understand the basis, potential use, and limitations of lifespan ratings, see our blog post ”How accurate are the average life expectancy ratings of home components? Are they actually useful?”
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Here’s links to a collection of our other blog posts about PLUMBING PIPES:
NOTE: These life expectancies are based on data provided by InterNACHI, NAHB, FannieMae, and our own professional experience. Because of the numerous variables that can affect a lifespan, they should be used as rough guidelines only, and not relied upon as a warranty or guarantee of future performance.
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