Magnetic water treatment
Magnetic water treatment (also known as anti-scale magnetic treatment or AMT) is a controversial method of supposedly reducing the effects of hard water by passing it through a magnetic field, as a non-chemical alternative to water softening.
There is a lack of peer-reviewed laboratory data, mechanistic explanations and documented field studies and erroneous conclusions about their efficacy are based on applications with uncontrolled variables,  Magnetic water treatment is regarded as unproven and unscientific.
There are, however, some studies which have claimed significant effects and proposed possible mechanisms for the observed decrease in water scale.
Vendors of magnetic water treatment devices frequently use pictures and testimonials to support their claims, but omit quantitative detail and well-controlled studies. Advertisements and promotions generally omit system variables, such as corrosion results or system mass balance analyticals, as well as measurements of post-treatment water such as concentration of hardness ions or the distribution, structure, and morphology of suspended particles.
Duration of exposure and field strength, gradient, rate of change, and orientation along or perpendicular to flow are variously cited as important to the results. Magnetic water treatment proponent Klaus Kronenberg proposed that the shapes of solute lime molecules are modified by strong magnetic fields, leading them to precipitate as spherical or round crystals rather than deposit as sheets or platelets of hard crystals. Simon Parsons of the School of Water Sciences at Cranfield University proposed that the magnetic field reduces the surface charge on small particles, increasing the tendency to coagulate as large particles that stay with the flow rather than depositing as scale. However, an internal study in 1996 at Lawrence Livermore National Laboratory found no difference in preferred crystal structure of scale deposited in magnetic water treatment systems.
Liu et al.  and Coey and Cass published research in 2010 and 2000 demonstrating that magnetic treatment causes water containing minerals to favor formation of a more soluble form of calcium carbonate (aragonite rather than calcite). 
The effect of magnetic treatment depends on properties of the pipe. The magnititude of the effect depends on pipe conductivity and surface roughness.
There are related non-chemical devices based on a variety of physical phenomena which have been marketed for over 50 years with similar claims of scale inhibition. Whilst some are effective, such as electrolytic devices, most do not work.
- Electrolysis: Electrolytic scale inhibitors - two metals such as copper and zinc are used
- Electrostatic: Electronic water conditioners
- Electromagnetic: fluctuating electromagnetic fields are created
- Other devices combine these different methods
Other uses of magnetic devices:
- Two studies have shown a statistically significant reduction in calculus formation on the teeth when exposed to magnetically treated water (as compared to normal water) with an oral irrigator.
- Magnetic fuel savers are similar magnetic devices marketed as saving fuel, but have no effect, as hydrocarbon fuels have no appreciable electrical resistivity and conductivity and are not susceptible to magnetic attraction.
- Loraine A. Huchler, P.E., MarTech Systems, Inc., Lawrenceville, NJ (22 Oct 2002). "Non-chemical Water Treatment Systems: Histories, Principles and Literature Review" (PDF). International Water Conference (IWC), Pittsburgh, PA, USA 2002. Retrieved 12 July 2014.
- Keister, T (2008). "Non Chemical Devices: Thirty Years of Myth Busting" (PDF). Water Conditioning & Purification. Retrieved 2009-12-11.
- Chaplin, M. (26 July 2011). "Descaling of Water". Water Structure and Science. London South Bank University. Retrieved 2012-03-26.
- Szkatula, A; Balanda, M; Kopeć, M (2002). "Magnetic treatment of industrial water. Silica activation". The European Physical: Journal Applied Physics 18: 41. Bibcode:2002EPJAP..18...41S. doi:10.1051/epjap:2002025.
- Powell, MR (1998). "Magnetic Water and Fuel Treatment: Myth, Magic, or Mainstream Science?". Skeptical Inquirer 22 (1). Retrieved 2007-10-26.
- Lower, S. "Magnetic water treatment and pseudoscience". Chem1Ware Systems Limited. Archived from the original on 2008-05-01. Retrieved 2009-10-25.
- Limpert, GJC; Raber, JL (1985). "Tests of nonchemical scale control devices in a once-through system". Materials Performance 24 (10): 40–45. OSTI 6089699.
- Smothers, KW; Curtiss, CD; Gard, BT; Strauss, RH; Hock, VF (15 June 2001). "Magnetic Water Treatment" (PDF). Public Works Technical Bulletin 420-49-34. U.S. Army Corps of Engineers.
- "Interview of Klaus Kronenberg, Ph. D". GMX International. Retrieved 2012-03-26.
- Krauter, PW; Harrar, JE; Orloff, SP; Bahowick, SM (1996). "Test of a Magnetic Device for Amelioration of Scale Formation at Treatment Facility D" (PDF). Internal Report (Lawrence Livermore National Laboratory). OSTI 567404. Retrieved 2009-12-11.
- Liu, C. Z.; Lin, C. H.; Yeh, M. S.; Chao, Y. M.; Shen, P (2010). "Surface Modification and Planar Defects of Calcium Carbonates by Magnetic Water Treatment". Nanoscale Research Letters 5 (12): 1982–1991. doi:10.1007/s11671-010-9736-5. PMC 2991221. PMID 21170405.
- Coey, JMD; Cass, S (2000). "Magnetic water treatment" (PDF). Journal of Magnetism and Magnetic Materials 209: 71–74. Bibcode:2000JMMM..209...71C. doi:10.1016/S0304-8853(99)00648-4.
- Alimi, F.; Tlili, M. M.; Amor, M. B.; Maurin, G.; Gabrielli, C. (2009). "Effect of magnetic water treatment on calcium carbonate precipitation: Influence of the pipe material". Chemical Engineering and Processing: Process Intensification 48 (8): 1327. doi:10.1016/j.cep.2009.06.008.
- Coetzee PP, Yacoby M and Howall S (1996) The role of zinc in magnetic and other physical water treatment methods for the prevention of scale. Water SA, 22(4): 319-326.
- López-Sandoval E, Vázquez- López C, Zendejas- Leal BE, Ramos G, San Martín-Martínez E, Muñoz Aguirre N, Reguera E (2007) Calcium carbonate scale inhibition using the "allotropic cell" device. Desalination 217:85-92.
- Pernot B, Euvrard H, Remy F and Simon, P (1999) Influence of Zn(II) on the crystallisation of calcium carbonate application to scaling mechanisms. Journal of Water SRT-Aqua, 48(1): 16-23.
- MacAdam J PhD Thesis Cranfield University UK. Dept of Water Science and various studies
- Whitaker, S (5 August 2011). "Guardian launches electrolytic scale inhibitor". Industry Today. Retrieved 2012-02-24.
- Watt, DL; Rosenfelder, C; Sutton, CD (1993). "The effect of oral irrigation with a magnetic water treatment device on plaque and calculus". Journal of Clinical Periodontology 20 (5): 314–7. doi:10.1111/j.1600-051X.1993.tb00366.x. PMID 8501270.
- Johnson, KE; Sanders, JJ; Gellin, RG; Palesch, YY (1998). "The effectiveness of a magnetized water oral irrigator (Hydro Floss) on plaque, calculus and gingival health". Journal of Clinical Periodontology 25 (4): 316–21. doi:10.1111/j.1600-051X.1998.tb02447.x. PMID 9565283.
- Allen, M (25 August 2010). "Looking For A Miracle: We Test Automotive 'Fuel Savers'". Popular Mechanics. Retrieved 2012-03-26.