Brass, plastic, and stainless steel are some of the materials that the current domestic industry manufactures fauces from. The most commonly sold taps however are manufactured from copper, with China being the industry’s top distributor. Copper faucets are fused with zinc, forming brass. To make the brass easier to cut, it is also mixed with a small amount of led. Without the inclusion of lead the faucet would be harder to cut, forge a poorer performance, and maintain a poorer resistance to stress corrosion.
Lead is a heavy metal and a well-known factor in harming human health, yet mainstream faucet production in Europe and America continue to be made from brass and copper with minor lead inclusion. In North America, NSF/ANSI 61-2012 is the baseline faucet toxicity standard. It mandates that the lead particles to not exceed 5 micrograms to be deemed safe for human use.
NSF/ANSI 61 was prepared as a testing standard by the National Sanitation Foundation (NSF) who conducted in-depth research and analyzed the component inclusion volume of heavy metals in products that are currently used in North America. While not a formal standard in other countries and regions, including China, this evaluation of heavy metal precipitation is widely accepted by the global community.
The NSF/ANSI 61 – 2012 Standard
The NSF developed the “Drinking Water System Components – Health Effects.” The standard’s initial edition in 1988. After several revisions, the latest version, formally released in 2012 (and classified as NSF/ANSI 61-2012) updates the standard to include pipes, fittings, valves, protective and sealing materials, and end products (such as taps).
Section 9 of NSF/ANSI 61 is a particularly influential and authoritative clause in the North American standard from a system testing perspective of faucets. Section 9 defines a faucet as an end product and measures the effect of heavy metals and organisms per 1 ltr of water. The test is performed by taking three complete tap sets and pretreating them on Friday afternoon. First, the faucet is rinsed with tap water and then filled with soaking liquid. The soaking solution is changed every two hours from 9:00 to 1700, 5 times per day. On days 3,4,5,10,11,12,17,18, and 19, extracts are collected for lead. The extracts for the other heavy metals are collected on day 19 at 9:00.
Because the precipitation of lead content is dynamic, the amount will vary from one soaking period to the next. The NSF quantified the average amount of precipitated lead at a given time with the application of statistical principles, calculation of standardized concentration via the logarithmic mean and standard deviation, and calculated the statistical value Q used for lead detection.
The standardized concentration is derived with the following formula:
NF = N1 x N2 x CMV
N1 in the above equation consists of (SAF/SAL)VL/VF(static)N2VF(static)/VF(flowing) = 1NSAF. That is the area of product overflow, Sal is the product’s area of immersion testing, VL is the volume of the water used during testing, VF(static) is 1 L, and CMV is the conditioning factor of the cold water (equivalent to cold water-filled volume/total water-filled volume).
You=InXij is the formula issued to calculate the natural logarithm of standardized concentration. The logarithmic mean for each of the 3 samples is performed with the formula (Yi = (Yi3+Yi4+Yi5+Yi10+Yi11+Yi12+Yi17+Yi18+Yi19)/9). After calculating the value of the logarithmic mean, the Q value can be compiled by the formula where K is the constant of the statistical parameter and depends on the test sample size when there are 3 test samples (K=2.6028).
Based on the last 8 years of testing with the NSF/ANSI 61 standard as the first third-party testing organization in mainland China, the following conclusions were reached.
● While lead content participation is variable and dynamic, the trend in its presence is gradually decreasing.
● The most common heavy metals that lead to standard failure are lead, copper, zinc, cadmium, arsenic, etc.
● As indicated by statistical analysis, 92% of the test results passed, and 8% failed. Of the failed cases, the Q value of lead precipitation failed to account for 3%, while the other heavy metals (zinc, cadmium, copper, arsenic, chromium) accounted for 1% each.
NSF/ANSI 61’s Impact On The Faucet Industry
With the ASMEA112.19.1/CSAB125.1 testing standard, the maximum lead content permit in copper tangential to water is 8%, but the concern among many manufacturers is that the use of lead in copper makes the NSF/ANSI 61 doomed to fail. For this reason, many enterprises are opting to change and will choose a lower lead level in copper, or avoid lead use altogether. This, however, changes the process and the changes raise costs.
Some enterprises will use a method based on a principle of copper-lead melting point difference known as “lead washing.” Lead’s melting point is 327.5 degrees Celsius, and the faucet casting temperature is 1000 degrees Celsius. This causes the lead to melt into the copper product more on the outside than on the inside.
“Lead washing” the products before they leave the manufacturers’ facilities mean the use of a chemical reaction process by treating the samples with a high alkali solution to wash away the greasy material from the surface, then treating it with strong acid. This will result in the lead in the copper faucet to quickly decompose. Washing lead reduces the content below the 8 micrograms acceptable limit of NSF/ANSI 61 down to just 4.1 micrograms, with a significant reduction in the Q value.
Summary
Most of the controversy behind lead in copper faucets is due to testing methods. Some agencies in the industry use the industry recommended approach, some apply the national standard, and some develop their own testing methodologies. Because of the variety of testing methods, there is no uniformity when lead content is reported on by the media and inconsistency in how the information is presented to the public. Therefore, we recommend that the NSF/ANSI 61 standard be implemented enterprise-wide as a mandatory test for faucet testing of a variety of different heavy metals.
