What is the average life expectancy of copper pipe?
Friday, July 27, 2018
Copper water supply pipe should last 50 to 70 years, and possibly longer. 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.
Another cause of copper pipe leakage 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.
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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