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Water Treatment: An Overlooked Component Of Wet Heat

April 1, 2004

In the old days, except for the occasional potato forgotten in a steam boiler, water treatment was not even considered.

In the good old days, hot water heating systems were built with fewer component metals, and nothing resembling the PEX products that are now in use today for underfloor systems.

Dirty water and corrosion in pipes was accepted. And if a heating system needed repairs due to corrosion, well, that was considered normal. In fact, except for the occasional potato forgotten in a steam boiler (old time railroad men cooked their potatoes in their steam boilers, forgotten potatoes released potassium phosphate, which reduced scale formation), water treatment was not even considered.

My, how things have changed in this modern era of home heating and hi-tech components. The diversity of metals in the system presents a complicated treatment problem that needs to be solved. If it is not solved, trouble awaits the contractor and the customer.

The reason for the existence of corrosion and scale in these systems has to be understood. How does it happen? Why does it happen?

The most common cause of corrosion in hydronic/radiant systems is oxygen. One oxygen source is the fill water that is put into the system. Cold water has the capacity to hold more oxygen. When the water is heated, oxygen is released. This free oxygen needs to be scavenged or removed from the system.

When it isn't taken care of, the oxygen attacks the system metals causing pitting and corrosion. The result of corrosion can be pinholes in the system pipes, with particular effect on any copper present. In addition, a large amount of metal corrosion particles are dispersed into the water, causing blockages and erosion to circulating pump impellers and seals.

Scaling is the result of calcium precipitating out of solution when the water is heated. The calcium is then deposited, binding with the system metals, particularly at the heat exchanger surfaces where the temperature is the highest. This quickly lowers system efficiency by reducing the rate of heat transfer to the water and allowing more heat to escape out the flue stack.

Again, the source of this calcium is the water being used. For this reason, it is a good idea to know what the water you are filling the system with contains. Some guidelines for good quality water are the following:

pH of 7.0-8.0.
Calcium hardness and alkalinity levels of 150 ppm or less.
Chloride readings under 50 ppm.
Normal conductivity will be 500 or less, and the water should be clear, colorless and free of any visible sediment.
Poor quality water should not be used. De-ionized or softened water should be used when the fill water is extreme.

In addition, systems containing glycol should be tested annually for proper freeze protection and pH. Even though inhibited anti-freeze is often used, the glycols can break down over time to form acids that will lower the system water pH, increasing the potential for corrosion and reducing freeze protection.

Some new boilers on the market today contain aluminum. Special care should be taken when aluminum is present in a boiler. Most inhibited glycols and water treatment products on the market will raise the pH of the water too high and have no ingredient for aluminum corrosion protection. Following the manufacturers recommendations as to cleaning and treatment or contacting a reputable water treatment company are a must when using these boilers.

As you can tell, this is not always an easy situation to control. This is the reason the new cleaners and treatments have such complicated formulations and why treatment has become a necessity.

Two Steps

Proper water treatment entails a two-step process. First, a system needs to be cleaned and, second, it needs to be treated. This is true whether it is a new system or a system currently in use.

Let's start with a new system that has never been in service. It is amazing what flushes out of a new system when it is cleaned after installation. New systems have an abundance of contaminants within their nooks and crannies. These range from solder flux to cutting oils, and everything in between including metal shavings, sawdust and dirt.

Anything in the air during construction can end up in the system. The cleaning product used should not only be safe for all system components, but also should dissolve all types of oil, dirt, rust and debris, and prepare or “passivate” the metals to set up the system for further treatment.

The proof that this needs to be done is in the ugly mixture that gets flushed out of a new system. The flush comes out filthy, at the far end of the spectrum from clear. Just do it once, and you will convince yourself.

Cleaning an existing system is another story. If the system appears to be dirty and not running efficiently, it should be cleaned of built-up scale and corrosion. It needs to have the sludge put back into suspension so it will flush out.

Treating a system, the second step in this tandem process, greatly increases the potential for a trouble-free life. The problems that are prevented are numerous, but the most important factor of all is that the efficiency of a system is maintained and, therefore, the system costs less to operate.

A good treatment product should meet the following requirements:

Contain corrosion inhibitors for all system metals.
Inhibit or prevent scaling.
Help control pH levels.
Contain an oxygen scavenger for quick oxygen removal.
Be safe with all the metals found in new systems, including copper, brass, mild steel, aluminum and stainless steel.
It should be safe on all soft system components, i.e. tubing and seals.
It should be compatible with new aluminum boilers.
It should be compatible with ethylene and propylene glycol.
There should be some method of testing the treatment.
The treatment supplier should provide technical assistance as needed.

Show a client pictures of what happens when a system is not treated and let him make the choice. It's his system. It's his choice.

Consequences

Still skeptical whether this should be done routinely as part of an installation or to maintain an existing system? Here is a list of possible negative consequences. This results from no cleaning, no treatment, poor treatment or the wrong treatment:

A new boiler shot in less than two years of use due to corrosion. A true story.

Corrosion pinholes in the copper piping. These tubes are usually thin- walled and excellent corrosion targets.

Corrosion at elbows and junctions of different metals.

Scaling of heat exchangers with the resultant loss of efficiency. This means higher fuel bills.

Oxygen corrosion due to no oxygen scavenger.

Expensive repairs and down time. Good old Irishman Murphy will make sure this happens at the most inconvenient time.

The price of prevention is low compared with the expense of repairs. Poor system performance is the plain and simple result.

The list of possible negative outcomes should convince most contractors of doing the right thing for their customers. In fact, a way to make your bid appear more professional is to explain why cleaning and treatment are necessary steps in the installation process.

The prevention of future problems is a very good sales point. The fact that the system will operate at top efficiency is another. These critical extra steps will give your bid for the job a higher perceived value. It should make you stand out from the other bidders who are not up-to-date on what needs to be done with these new hi-tech systems. Bottom line, price is only one part of winning job bids.

Knowledge and professional work carry added weight with the smart consumer. Taking care of these critical steps is the sign of an informed professional contractor. A clean, well-treated system increases the likelihood for a long-term happy customer and a positive contractor reputation.