We are back with another article and this time we will look at water quality and its effect on water heaters and boilers.
Boilers are typically closed loop systems where fresh water is used to fill the system but the same fluid is used over and over again. After a system fill, very small amounts of fresh water will enter to maintain system pressure. Chemicals are added to inhibit corrosion and prevent freezing. The dissolved oxygen, calcium and other minerals will precipitate or “fall out” of the heating fluid. They only become present if fresh water is allowed to re-enter the closed loop system.
For instance, I experienced a scaled up heat exchanger on a properly installed closed loop boiler. After further inspection of the closed loop fluid it was found to be untreated fresh water. The maintenance crew had been using a boiler drain valve to extract heating hot water for cleaning purposes. This occurred every day where they would fill a 5-gallon bucket twice a day. They had access to a Domestic water heating system (right next to the boiler) that resolved their boiler scaling issue.
Water heaters are designed to heat volumes of fresh water up to temperature for domestic and potable uses. The fresh water can contain various minerals and chemicals that will shorten heater life or cause adverse conditions when heated.
Scale build-up is the single most cause of water heater failure and loss of efficiency. The nature of water heater design can be a definitive factor in longevity and overall efficiency but the water conditions are area, utility or site specific. Calcium is present in water and it wants to stick to heating surfaces as it changes from suspension to solids.
ANODE ROD PROTECTION
Most tank-type water heaters use a ceramic porcelain Glass lining to protect the steel vessel interior from fresh water. The glass lining requires a sacrificial anode to cover and protect any weak spots on the lining. Electrolysis will attack the weakest spot on the lined tank interior and the anode is designed to give itself up to fill that particular spot. Over the life of the heater the anode will sacrifice or “give up” small amounts of its soft metal to protect the lining.
The two metals most commonly used in water heaters for anodes are either Magnesium or Aluminum. These metals are softer than steel and less noble. They can sacrifice themselves prematurely if attacked by the content of the water. These have distinct signs and smells that help to recognize how to deal with such issues.
Here are some common water problems related to water heaters and anode rods:
Hydrogen Sulfide – reaction created by a sulfate-reducing bacteria. It occurs with water that has high sulfur content and it attacks the magnesium anode. It is referred to as “Rotten Egg” smell. Hydrogen Sulfide gas in large quantities can be toxic and explosive.
Hydrogen Sulfide normally can be corrected by changing to an aluminum anode rod after performing a complete chlorination and flush of the tank and piping to kill the bacteria. Some manufacturers specifically use an aluminum anode rod as standard equipment in Florida to avoid the reaction to magnesium.
Aluminum Hydroxide – reaction caused by high pH water. It occurs many times in areas with high chlorine/chloramines in the water supply. Chlorine has a very high pH of 11.7. This reaction forms a jelly-like substance on the anode rod and in the bottom of the tank. It can appear as grey, blue or green beads or gel. The odor produced smells something like week-old trash so it is not something you can tolerate very long!
High pH also means alkaline or scaling so the tank must be flushed out and possibly de-scaled. The reaction is treated with the other viable anode made of magnesium.
Water Softeners – water softeners reduce grains of hardness through a process of ion exchange. Most water softeners exchange sodium (salt) ions with insoluble calcium and magnesium ions. Sodium can increase electrical conductivity and accelerate anode consumption. Use of water softeners warrant monitoring of pH level, conductivity and anode inspection at a regular interval, no less than once a year.
Stagnation – allowing the same water to exist in the tank for long periods of time will result in stagnation. The potential for bacteria increases. This can attack the anode and the results are smelly water and a heater that needs service. Many seasonal residents of Florida will leave their winter homes and forget to drain down their water heater. They typically turn off the power before they leave and the low temperature, stagnated water starts creating the perfect Petri dish. The other application is a larger storage heater that does not get used much, where very little fresh water enters to replenish the stagnated water. A 50 gallon heater on a break room sink is a great example of an over-sized and under-used heater.
Grounding – bad earth grounding can create an electrical potential that will erode the anode at a rapid rate. Once the anode is gone, the steel tank is attacked by the electrolysis.
NEW ANODE TECHNOLOGY
There is newer technology on water heaters for cathodic protection. Electronic controls can help to implement a non-sacrificial anode. The benefits of such a device are a milestone in tank protection.
The Powered Anode is a titanium rod that is immersed in the top of the heater tank. It can function as a Low Water Cut Off to insure that the tank is full of water. Titanium is a very hard metal, mostly impervious to fresh water and much more noble than steel. It will last longer than the water heater and does not sacrifice itself. So there is no smell that will be generated by this non-sacrificial anode rod.
The electronic controller will send out a micro-DC current to the Titanium rod to offset electrolysis. The electronic controller sends out more micro-DC voltage as the tank lining gets older. At some point, the electronic control cannot put out any more current. The integrity of the tank lining is so diminished it is already leaking or within days or weeks of leaking. This is a valuable feature, to know that when you cannot maintain power to the electronic anode rod, you are about to experience a tank failure in the very near future. Time to schedule a change out!
OTHER WATER ISSUES
Water can and will contain a variety of chemicals and minerals that can create adverse conditions when heated. The heating of the water will increase precipitation of scale. It causes the calcium to leave solution form and become a solid that sticks to itself and accumulates on heating surfaces.
High iron content is very common in Florida with well systems. Tannic acids will turn the water yellow to brown in color. Lime is naturally present in every water source to some degree. Bacteria can also be thriving in a particular water supply. The process of heating accelerates the various reactions. There is a wide range of targeted treatment and filtration products that can address these such as UV, Iron filters and the like.
It is important to remember that it is not the fault of the water heater, but a adverse reaction to the water…