Scale test provides credible metric of physical water conditioner performance
The International Association of Plumbing and Mechanical Officials (IAPMO) may not be familiar to everyone in the water treatment industry, but for plumbing professionals, alongside their fellow standard custodians ICC-ES, it is known as the “plumbing police.” IAPMO writes the Uniform Plumbing Code for residential and commercial plumbing. IAPMO recently published the first U.S. independent performance standard for physical water conditioners (PWC): the IGC 335 Rapid Scaling Test. Early results from this test protocol have shown impressive and surprising results.
A Different Approach
To understand these results, first it is necessary to understand what PWCs do, what the chemistry is and how they differ from conventional water softeners.
Hard water contains dissolved calcium in the form of calcium bicarbonate (CB), as well as other dissolved salts. CB has two unusual characteristics. The first is that it is less soluble in hot water than cold. When CB comes out of solution (precipitates), it converts to calcium carbonate (CC) and the byproducts are carbon dioxide and water. In addition to increased temperature, precipitation also occurs due to a drop in pressure or an increase in pH, known as a scaling event.
The second unusual characteristic of CB is that when CC starts to form, or nucleate, it has to do so onto something else; it cannot precipitate on its own. This is why it sticks to surfaces as scale and causes problems in plumbing systems, including clogging pipes and heaters, causing wasted energy and other problems associated with hard water.
Historically, water treatment solutions have focused on removing the calcium ion from water and replacing it with other ions that do not stick to surfaces, but what if there were an alternative technology that stopped the CC from sticking to surfaces? That would solve one of the biggest problems associated with hard water.
This is exactly what physical water conditioners do. Generally speaking, they generate an alternative “nucleation seed” in the hard water prior to the scaling event so when the scale precipitates, it tends to do so on the nucleation seed instead of the surfaces it normally would. The scale, rather than being stuck to a surface, is now held in suspension in the water as a fine powder. It will be carried away by the flow of the water as a fine particle of CC, much like chalk dust. It might deposit on surfaces when the water evaporates, such as on shower screens and work tops, but it easily can be wiped away because it is not sticking to the surface. There is no need for chemical cleaning using acids.
Once formed by precipitation in suspension, the scale is stable and will not revert back to its dissolved state unless the pH is reduced. It will not react with soaps, reducing lathering and producing scum in the same way that soap behaves in conventionally soft water. The water contains the same amount of calcium, but now it is in a solid form, CC, rather than the dissolved form, CB.
What are these nucleation seeds? Published scientific papers have identified a number of different elements that are effective in this respect. Zinc currently is the most widely used but iron and polyphosphates also are effective. CC acts as a seed if it can be generated and released in the water. Zinc dosing using electrolysis can be effective, and there are many academic reports on the subject, including some by Jitka Macadam and Simon Parsons at Cranfield University. However, there is a significant problem with the reliability of zinc dosing due to passivity, the tendency for the contributing zinc anode to scale up itself. Unless it is cleaned or replaced on a regular basis, the performance falls off quite quickly, hence the poor reputation of magnets.
Macadam and Parsons also found that iron could act as a nucleation seed. They did studies using electronic water conditioners, but never accurately identified the processes involved. Unpublished research at Oxford University revealed the mechanism by which an electronic water conditioner can modify the structure of an iron ion to significantly enhance its effectiveness as a nucleation seed. One of these devices has been tested by IAPMO R&T Labs using the rapid scaling test protocol.
In the course of their studies, Macadam and Parsons adopted the rapid scaling test, a protocol that had been developed jointly by Fernox and Lifescience Products in the mid 1990s, for their evaluation. This protocol was later developed by Midland Corrosion Services in the U.K. to form the basis of a corrosion inhibitor test protocol. It also forms the basis of IAPMO’s IGC 335 rapid scaling test.
In its first iteration, IGC 335 is designed to test electronic water conditioners, but it can be adapted for other technologies. The core of the test is an approximately 1-liter glass container containing the test water that is heated by an immersed electric heater to 180°F for 23 hours. The heater is covered with a stainless steel sheath where the scale precipitates. At the end of the test, the sheath is removed, weighed, cleaned with acid and weighed a second time, revealing the weight of scale that has accumulated. The test is repeated four times and the results averaged. Testing without treatment and then with PWC treatment reveals the performance of the PWC.
The water tested was from a residential faucet in the eastern part of the Las Vegas Valley where the source primarily is the Colorado River, pumped out of Lake Mead. The hardness was 300 ppm as CC equivalent.
The rapid scaling test uses a far higher temperature than normally found in domestic plumbing services in order to generate as much scale as possible in the 23 hours of the test. The rate of scale formation increases significantly at these higher temperatures, so an 83% reduction in the test rig would equate to a much bigger reduction at normal domestic temperatures to be found in the field.
IGC 335 offers the opportunity to test a range of PWC in a variety of test waters with a high degree of repeatability at a low cost. For the first time, it is possible to accurately measure and compare the performance of PWC’s both against each other and in varying water qualities. For a number of different reasons, the U.S. has been much slower than other parts of the world to adopt alternatives to conventional water softeners. Much of the reticence has been blamed on a lack of credible independent performance testing. The IAPMO IGC 335 rapid scaling test provides the opportunity to overcome this objection. It provides the basis for both the water treatment industry and the consumer to embrace alternatives for both the benefit of the environment and the consumer’s wallet.