Last month I revisited the after effects of neglected boiler system water and aluminum heat exchangers.  If you recall, you’ll remember the particular problem I encountered was a cracked heat exchanger and a loss of system pressure. The results were error codes flashing left and right with intermittent operation only made possible due to the incorporation of an automatic glycol feed system and a reset button on the boiler control. As I played detective on that particular case I was forced to refresh my chemistry knowledge only to realize that so much of what we service and install daily is deeply rooted in water quality or chemistry if you will.

One of the biggest issues we face with modern hydronic systems is the low operating temperatures specified upon design.  Heat delivery components such as high output baseboard, panel radiators and radiant tubing allow for any combination of installations utilizing ultra-low water temps. Unfortunately, this is also a veritable breeding habitat for micro-organisms, and this will almost surely lead to failure of individual components or the system as a whole if strict guidelines are not followed in respect to system fluid quality. These little critters thrive in wet environments (check) and can easily withstand aquastat settings below 160°F (check, again). The source of their entry into our heating systems can usually be traced back to the water used for filling during installation.  More often than not, and usually by design, that original fluid has never been changed. The microbial infestation has a perpetuating life cycle of eat, multiply and die. It’s the death part of the equation that has their little black bodies hanging around looking for a slow spot for their final resting space. Too often these tiny particles, when concentrated in large doses, are the victim of mistaken identity and written off as pieces of decayed hydronic components or piping.

Microbes aren’t the whole story

The many individual components that make up a complete hydronic system are often sourced from various vendors. Rarely will I install a complete system comprised of parts manufactured from the same source.  Add to that is the fact that many of the parts often are made of dissimilar metals.  Enter electrolysis. Water is a great conductor which provides the pathway for the most prevalent type of electrolysis; galvanization or galvanic corrosion. Corrosion is not limited to only ferrous metals though. Aluminum, as I talked about last month, is also susceptible to a similar corrosion with results as much or more devastating. Cast iron heat exchangers may be robustly built but, they are not immune to the laws of chemistry and pack a powerful punch of the cathodic variety.  What this means is when two dissimilar metals (iron, aluminum or stainless steel) are immersed in an electrolyte (water) one has to give way. The resulting aftermath will likely show its face in a “clogged” circulator, small diameter radiant tubing or a leaking air eliminator.

Electrolysis and microbial infestation separately are bad enough, having both over for dinner on the same night is nothing short of a nightmare but, believe it or not, they’re not the worst offenders to our highly sought-after hydronic bliss. Our biggest fears must remain focused on oxidation. Oxidation affects all types of metals in a heating system, some metals more than others. Upon initial fill, a system is ripe with oxygen in a dissolved state but, as the system heats up the dissolved oxygen will come out of solution and attack any ferrous component, such as cast iron circulators/exchangers or piping components. As the system cools any remaining oxygen that made it past any exit point then dissolves due to its low pressure state only to continue the oxidation cycle. Of course oxidation is most prevalent when materials installed do nothing to stop the diffusion process. Poly cross-linked tubing used as distribution piping or as a heat emitter must contain an oxygen barrier as its metallic counterparts have this built in. Any amount of money saved by specifying non-oxygen barrier tubing will be quickly negated in short order. Adding additional components to isolate the non-barrier tubing from the rest of the system will only solve half of the problem as oxidation problems will continue to exist in one side or another, but I’ll save that discussion for another column.

So what do we do about all of this?

There are an enormous amount of systems in commission today that have one or more of these problems. There is money to be made in providing a solution to system failures related to water quality issues and not just on the piece by piece replacement approach. Of course installing the proper components the first time, along with annual monitoring of system fluid and general maintenance could give us all a solid footing in the fight against the inevitable. Having a chemical treatment plan in place for all new installs and remodels would be a great way to increase your offering as a full service provider of all things “hydronica.” If you’re not sure where to start or are thinking you don’t have time to take on such an endeavor, contact your local supply house and ask what boiler system chemicals they keep on the shelves. Chances are there will be a manufacturer representative nearby willing to tell you all about their product and get you started down the right side of the road, all the while helping you put more money in your pocket.

As an aside, I’d like to thank a good friend of mine for helping me deal with these exact issues I’ve written about here. Rich McNally has been in this industry for longer than I’ve been out of diapers; in fact I think he’s even told me so. But seriously, Rich is a former math teacher, HVAC wholesaler, and a current industry leader on such subjects as it pertains to boiler systems and their components. I’m proud to call Rich a friend, and I hope you have chance to meet him someday if you haven’t already. You’ll find him heading up the Northeast sales management for Watts Water Technologies, so chances are you’ve been the recipient of his hard work to get the right information out amongst the varying hydronic channels in our industry.

Eric Aune started Aune Plumbing LLC in 2004, and to carry on the tradition of family members before him, he has specialized in residential and small commercial hydronic heating systems and service. He is a graduate of Dunwoody College of Technology and Plumbers Local 15, Minneapolis Apprenticeship Training Program, and is currently a United Association Instructor and teaches for the Plumbers Local 15 JATC. Aune is also founding partner and vice president of Contact him at: