Active Anode
Anode material that has been soaked in an weak acid (Sulfamic 25 g/l, Sulfuric 10% bv, or HCl 5% bv), to remove oxides from the surface, and activate the base metal for electroplating.

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September 27, 2004

The evolution of purifying the water we drink can be traced back to the Roman Empire, and possibly before that as well. Ion exchange procedures however, are a more recent development, as scientists began testing processes in the early 1800’s. The first recorded, and successful, ion exchange process occurred two centuries ago, and it consisted of exchanging ammonium ions (NH₄⁺) for Calcium ions (Ca²⁺), using ordinary clay. In 1912, cation exchange water softening was introduced in the United States. In 1935, synthetic cation, and weak-anion ion exchange resins were developed. It wasn’t until after WWII, that researchers discovered a new polymer, styrene-divinylbenzene (DVB). This discovery allowed complete de-ionization by ion exchange, including silica and carbon dioxide, to be accomplished. The polymer DVB was the breakthrough that revolutionized the water softening industry.

Why do we soften the water?
As I mentioned in Part I, normal city water contains the elements: Sodium, Calcium, Magnesium, Potassium, Iron, and Manganese. Hard water is caused by “hardness ions” found in the city water. Typically these hardness ions are Calcium, and Magnesium, but can also include Manganese, Iron and Aluminum as well. “Total hardness” includes all the hardness ions and is quantified in many ways; Grains per US Gallon (GPG); German- French- and Clark degrees (^odH, ^ofH & ^ocH); ppm or mg/l as Ca, CaO and CaCO3 (Calcium, Calcium Oxide & Calcium Carbonate). Most city waters are in the range of 5-15 GPG (~ 5-15^odH or 85-250 ppm as CaCO3).

Not only does hardness require more soap consumption, hardness ions have typically a rather low solubility together with other, in natural waters, common an-ions, and, opposite to most other salts, the solubility decreases with temperature. Water is considered hard when it exceeds 3 GPG (~ 3^odH or 50 ppm as CaCO3) of hardness ions. If the concentration of solubility is exceeded, typically on a hot surface such as the surface of a heater, a deposit of hardness salts, scale (predominantly CaCO3, se below), is formed. Scale reduces the heat transfer from the heater to the water, thereby the capacity and efficiency, and could cause the heater to burn out.

Scale can cause other problems in other applications. In the reverse osmosis (RO) process, the water impurities are concentrated almost 3 times and the risk of scale to be formed in the RO membrane is apparent if hardness is present.
However, it should noted that hardness prevents corrosion to some degree.

What happens to the RO if it is fed with hard water?
The RO works by passing pre-softened and carbon treated city water across the membrane. During this process, a substantial fraction of the water (2/3 of the input volume) is passed through the membrane, leaving an increased concentration of impurities along the pressurized side of the membrane. If the concentration of solubility of the impurities is reached, they will deposit as solid particles, scale. Once this scaling occurs, the capacity of the RO system is reduced. The process is typically fairly rapid and can cause the DI water to fail within a week. Removing the scale from the RO-membrane is possible, but difficult.

Instructional Tip #1 – Maintaining proper Active Carbon- and Softener Filters Pressure:
Within the plumbing setup, for the PW/1000, you will find a Pressure switch, which is located after the RO Inlet Valve, on the RO Pump Feed Water Line. The purpose of this switch is to keep the pump from running out of water, but will also indicate if the city water pressure drops below 25 psi, the point at which the active carbon- and softener filters may fail to regenerate properly. When the feed water pressure is reduced to 25 psi or less (due to fluctuating city water feed, from the input water line), the alarm will sound and the RO Pump will switch off. This switch is preset at the factory, to maintain the pressure greater then 40 psi, but sometimes it needs to be set lower at the customer’s site. This is done as follows:

1. Check the set pressure when the RO process is running by very slowly choking the inlet valve to the filter house after the softener filter. Monitor the pressure indicated on the pressure gauge at the filter house outlet. You have reached the present set pressure when the alarm is triggered. Open the choked valve and restart the RO pump to silence the alarm. 2. If the set pressure has to be changed; open the front cover of the pressure switch by unscrewing its four screws. Adjust the big hex with a wrench in small increments; unscrew (counter clockwise) to reduce the set pressure. Do not adjust the small hex or the setscrew on top of the big hex! Repeat #1 and #2 until you have reached the set pressure required.