Nickel is a trace element - essential in small amounts but hazardous when in excess. Although its impact on our health is a substantial issue, it is usually overlooked in sanitary engineering. Primary source of nickel in drinking-water is leaching from nickel plating of brass connectors used in drinking water installations. It may cause numerous side effects. It is worth knowing them.
Nickel in human body
Nickel supplies cells with oxygen, nutrients metabolism and hormones formation. Daily intake of this element for adults is about 0.3 mg and it is covered mostly by foodstuffs (grain, chocolate, fish, margarine and some vegetables, such as cabbage and onion). Moreover, nickel can also be inhaled (air contaminated with industrial gases and dusts) or get through with drinking water, if the water supply system uses nickel plated components for surfaces coming into contact with water — installation connectors or water supply fittings.
What is the acceptable concentration of nickel in drinking water? It is defined by the EU Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. The highest acceptable nickel concentration is 20 µg/l, which puts it in the group of the most toxic metals. For comparison, the concentration of lead and arsenic, unequivocally associated with health hazard, may amount to 10 µg/l; chromium is slightly less toxic (50 µg/l). The acceptable concentration of copper is about 2 mg/l which is hundredfold higher than that of nickel!
Excess or deficiency?
Even though nickel deficiency has adverse effects for organism, it is usually excluded by using a varied diet. Its excess, however, is more hazardous. It may cause damage to mucous membranes and changes in chromosomes and marrow or even the development of cancer cells. Most common side effect of nickel excess is contact or food allergy. Contact nickel allergy results in rash in a place where skin touches a nickel plated item. Food allergy symptoms include runny nose, conjunctivitis, it may lead to asthma or even anaphylactic shock. It happens that nickel allergy results in rejecting orthodontic and orthopaedic implants and negatively influences the element balance in body — it reduces the magnesium and zinc level in parenchymal organs. No method of curing nickel allergy is known and the only recommendation is to avoid products containing this element.
Installation systems with nickel plated connectors
What is the practice of using nickel plated connectors in water supply systems? The problem is mostly with the multi-layered pipe system components (press and screw couplings) and polypropylene (threaded couplings). Connectors in such systems have hygienic approvals allowing them to be used in drinking water installations. Admittedly, the product information states that it contains brass, but it omits the fact that the brass is nickel coated and the coating comes in contact with water.
Why are brass connectors nickel plated? One of the reasons is that it improves connector aesthetics, but it is not the main reason. Most of all, nickel plating allows additional protection of lower quality brass susceptible to dezincification (that is corrosion process), as well as high concentration of heavy metals, e.g. lead. In polypropylene profiles with brass fusions there is one additional factor — cheaper polypropylene granulate is susceptible to copper ions released from brass. To avoid it, polypropylene enriched with suitable inhibitors should be used.
KAN-therm company actions concerning connectors nickel plating
To avoid the hazards of nickel exposition, in its KAN-therm Push, Press and PP installation systems KAN uses connectors without any additional coating which would contain nickel. They are made of PPSU (completely neutral for drinking water) and brass susceptible to dezincification which can be safely used in water supply systems.
Using PPSU solves the issue of nickel plating connectors in installation systems used in water supply, central heating, compressed air and other systems.
Nickel plated profiles which are used in installations to transfer water intended for human consumption have a broadly negative perception. Such profiles are a source of remarkable amounts of nickel transferring into the water and as a result, concentration of this metal in water exceeds the acceptable limits. Even though such connectors can be used in heating systems, producers should not recommend to use the same connectors for both water and heating systems.
During meetings with Investors and Contractors we are often asked: "Why do you endeavour to point out threats resulting from using nickel plated connectors, even though in your offer you have KAN-therm INOX System made of stainless steel?" True, KAN-therm INOX System uses pipes and connectors made of nickel-chromium-molybdenum or nickel-chromium-titanium which contain 10 to 13% of nickel. Nickel migration tests confirm that in case of stainless steel this process if substantially smaller than in case of nickel plated coatings, and therefore the metal concentration in water does not exceed the acceptable limits. KAN-therm INOX System in drinking water installation is completely safe and approved also by such certificates as DVGW - the largest gas and water industry certification body in Europe.
Recommendations concerning usage of nickel
National Institute of Public Health gives particular data concerning the effects of nickel plating of the connectors and points out what actions should be taken. It states that:
In all equipment in contact with drinking water, the nickel and nickel-chromium coating can be used only on the outer surfaces which do not have direct contact with water;
The contact of nickel coating with water results in a very high concentration of nickel in water. Nickel migration tests showed that the concentration reaches the value of 200 to 350 µg/l, which exceeds the standard (20 µg/l) 10-15 times;
Previous hygienic approvals did not include a stipulation that the nickel coating can be used only on the outer surfaces because it was believed to be obvious. The possibility of using products with inner nickel coating did not seem real (especially in products such as taps and valves). Unfortunatelly, regularly manufacturers of pipe connectors do not provide information of nickel plated brass in their goods;
Attestations and certificates
Similarly as with the recent increase in awareness of smog harmfulness, it is crucial for the subject under discussion to come into public attention informing about the threats resulting from using nickel plated components in water installations. Investors should know that even formal confirmation such as the hygienic approval concerning the possibility to use a particular product does not necessarily mean that it was issued on the basis of full data and in accordance with the Legislator's intentions.