Great news. The job is done. Just fill up the boiler and distribution system and call it a day. Well, not so fast.

There could be problems with the water quality, which may lead to serious issues. And to think, you almost unleashed them on your gorgeous, newly installed hydronic system. Talk about creating your own risk of callbacks.

Over the years, I’ve come to learn a thing or two about how our water quality nationwide has suffered significantly. As aquifers have been reduced substantially, all sorts of contaminants have been stirred up in them. And, if the water that would be used to fill your new mechanical masterpiece comes from a municipal source, there are plenty of issues causing problems there, too. Consider Flint, Michigan. As a hydronics contractor, corrosive water ranks among the nastiest of challenges.

And, as more pollutants, germs, and other unwanted crap enter our water sources, they can wreak havoc inside hydronic systems. These impurities can lower the heat-transfer capability of a heat exchanger and clog fire tubes, which may cause a reduction in flow, shorten the system’s life expectancy, and beat system efficiency into oblivion.

Just a decade or two ago, clean, well-balanced water was still abundant.

Today, there’s plentiful bacteria, particulates, and runaway pH. With these factors and more, you begin to understand my reluctance to simply fill a newly installed hydronic system.

Even free oxygen can cause unchecked corrosion. Scale buildup, especially on heat exchangers, is another conundrum. Imagine the effect of roaming minerals on sensitive pumps and valves.


Oxygen is a silent, stealthy killer. Of course, as kids, we learned that everyone needs oxygen, but for hydronic systems — boilers, especially — it’s a slow-killing venom.

The biggest, ugliest dude on the block is oxidation, which, when plentiful, can have its way with all types of metals and other system materials. For example, consider the essential function of steel boiler firetubes. With oxygen present, they oxidize, becoming frail before rupturing.

Oxygen comes from various sources. When water is heated, dissolved oxygen will come out of solution to attack ferrous components. When it’s cold, highly pressurized water (from the source) enters a heating system. But when we take all that pressure off it, the oxygen comes quickly out of solution.

Then, when heat is applied, corrosion rates double every 18°F rise in temperature. Imagine the impact with a short-cycling boiler or a system that adds new, oxygen-rich makeup water to enter freely.

I had a customer once who could not get her bathroom radiator to function. She wanted heat in there. She explained to me that she would bleed it every so often for years, then fill the system back up with a washing machine hose connected to a utility sink spigot. Just imagine the damage all that makeup water had caused.

Of course, most of the damage that happens is undetected and unseen. If conditions remain this way for some time, the water chemistry will change. Eventually, there is a drop in pH, which creates an acidic brew that’s bad to the core.

We’ve learned that water with a pH level of 7.5 is neutral, which is good. But a short fall to 6 will eat components like Amazon River piranha eat other fish.

So, by all means, be sure to check the pH of water before you give your new “baby” a drink. But it’s good to know, too, that water pH levels can change; one of the more common reason for falling pH is due to expired propylene glycol antifreeze.

Glycol absorbs oxygen as it ages, which is good, but it loses PH at the same time while its freeze protection diminishes, which is not so good. If your new system is filled with a partial glycol mix, it should be checked annually. That can be a good thing, too. After all, you’re in the profitable service business, right?

Just a reminder: This is what that refractometer is for. It only takes a minute to use.


Another problem with water can be microbial, and bugs and germs can create entirely new problems if left unchecked. Give them a nice warm place to huddle and make plans, and then watch them multiply and spread throughout your vast radiant heat system. This results in a monumental headache.

In fact, this can be an especially big challenge with low-temp radiant heat systems. As they live and die, they create a black sludge that’s often mistaken for decayed hydronic components or pipe.

One of their favorite “foods” is sulfur, which is plentiful in many New England aquifers. A sure sign of microbial corrosion is a rotten egg smell.

There are loads of other water quality challenges, including electrolysis. With so many dissimilar metals in hydronic heating systems, we can invite galvanic corrosion without even thinking about it. Water is an electrolyte, an electrical conductor; thus, proper grounding is important.

And, when metals decay, corrode, or oxidize, pieces gradually break away from components and migrate to places like pumps, mixing and zone valves, heat exchangers, and radiant tubing. Now, there’s a nice thought, huh?


I highly recommend products made by Fernox, which creates inhibitors, cleaners, filters, power flushing systems, and more designed specifically to combat the types of problems I’ve described.

Two of the products I often use are the TF1 Filter and the Protector F1 express inhibitor. The TF1 Filter is a bypass filter that typically gets installed on a system’s return piping. It houses a powerful magnet that picks up ferrous metal fragments that circulate in the hydronic system and safely holds on to them until the unit is flushed.

“Flush the unit?!” you ask. Yup — and it’s faster than ordering a fast food hamburger. The Protector F1 Express is an easy, fast, and convenient solution that maintains a system’s efficiency and prolongs a boiler’s life. I especially appreciate that it’s safe and suitable for all metals, including aluminum. A full system dose can be applied in 30 seconds or less. It’s simple and doesn’t cause a mess. Yet another benefit is that it protects against corrosion and lime scale.

So, when I find gear that’s made to make my job easier, helps me do my job better, doesn’t waste my time, and greatly reduces the risk of late night, mid-winter callbacks, I’m all for it.

Publication date: 6/20/2016

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