Water Quality Can Make or Break a Hydronic System

Water quality. If you haven’t spent a good deal of time thinking about it and the impact it has on your hydronic heating system, think again. In fact, it’s so critical to the performance of the system that the installation and maintenance of the system should never be done without consideration of how to maintain the water quality that keeps the system running.

Any untreated system with iron pipework is susceptible to the perils of corrosion, which can sap as much as 15% from heat-transfer rates and up to 6% from boiler efficiency rates after only three weeks. These declines are not only unexpected, but also unacceptable to building and homeowners who expect their high-efficiency equipment to consistently save them money over the long run.

So what’s a contractor or service technician to do? Most turn to some sort of filtration method, which pulls iron oxide out of the system. These are typically used alone or in combination with system treatment formulas made to clean or inhibit corrosion. It’s a start, but there’s much more to consider.

Not your father's boiler

High-efficiency boilers and circulators are increasingly being installed for the reduced heating costs and lower carbon emissions they make possible. However, it’s vital to understand how important water quality is in maintaining these units’ efficiencies.

The very features that make them efficient, such as their narrow waterways, mean that issues such as system-clogging magnetite have an even bigger impact on their performance.

Magnetite is an iron-oxide sludge that forms as air and water mix inside the pipes of an untreated hydronic heating system. As these small (.0003-micron) particles circulate and accumulate inside the system, they begin to adversely affect heat-transfer rates and boiler efficiency. More importantly, iron oxide buildup can lead to equipment damage and/or failure, which then leads to costly repair.

The most obvious benefit of treating hydronic system water for the home or building owner is that the heating system works more efficiently, meaning it will use less energy and, therefore, will be less expensive for them to operate. Also, they’ll get a more even heat distribution throughout the structure, eliminating the need to constantly turn up the thermostat to increase the setpoint temperature in different rooms.

Finally, the heating system is less likely to suffer breakdowns, because critical components — such as the heat exchanger and the pump (circulator) — are protected from the dangerous iron oxide that is lurking in the system. Deposits of magnetite tend to accumulate anywhere there are low-flow areas in the heating system.

Low-flow areas

Very often you find that, depending on how the system is plumbed, low-flow areas are created where new parts have been added to a system, for example, where you have an extension of the system into an addition on the home.

Frequently, the extension contains “dead legs.” For example, if you build a ground-floor extension onto a home or building where you have radiators, you would ideally want to plumb from the downstairs pipework. But if you have a solid floor, sometimes in order to avoid digging up that floor, the contractor will come up to the first level and lift up some floor boards to access the pipework directly beneath. Then he’ll plumb it from the first floor back down to the ground floor, creating a drop in the heating system. The pipe will go down and then feed that radiator, and then it will go back up and reconnect to the first floor pipe works.

It is incredibly difficult to clean out that section, and you would need a very high head of pressure in order to push any debris down the pipe, and then back up the pipe and out the drain. This type of scenario can occur in commercial and residential installations.

In addition to these engineered low-flow areas, radiators and baseboards — by the nature and intent of their designs — slow the flow of system water, so these are natural low-flow areas where iron oxide can collect and cause problems.

Combining chemical treatment and filters

So, why install a filter on top of using a chemical cleaner and inhibitor? The best way to explain it is to compare it to car care. You would still put an oil filter on a brand-new car; you wouldn’t wait for the engine to get a bit grubby before deciding to fit a filter onto it. That’s the same theory behind installing a filter on a hydronic heating system, even if you’re using chemicals.

In a heating system that is old and has been installed for quite some time, even if you clean it and use an inhibitor, you can never guarantee it would be 100% cleaned. Modern components in heating systems are actually very susceptible to debris. Modern condensing technology is marked by incredibly fine flows, and they can be blocked with very small amounts of debris.  So best practice is always to use a filter, even if you have used a cleaner and an inhibitor.

It’s also important to keep in mind that an inhibitor is not a preventer. It slows down the rate of corrosion, but does not necessarily stop all of it, and the inhibitor can get used up in that process. This is why, in the U.K., commercial systems are very strongly regulated to make sure there is always the right amount of chemical in the system. These systems must be checked four times a year from multiple system checkpoints, because of inhibitor degrades.

On a residential system, it’s completely impractical to expect to get into a household more than once annually to check on what’s happening inside that system. So we recommend instead to check the heating system water annually, and every fifth year, top off the inhibitor in the system, compensating for any degradation.

Air separation

How important is automatic air separation in residential and commercial magnetic filters? If you have a need to remove air from a system, you need to do it from the flow side of that system. If you need to remove magnetite, you need to do it from the return side.

Those are different technologies on different parts of the system. Putting them together in one product doesn’t make sense from an engineering standpoint, but we see it done all the time, and we get asked to do it all the time. Which is why incorporating an automatic air vent on a filter is more a concession to the marketplace than a true system need.

ECM technology and filtration

In the U.S. market, that’s come about because, for a long period of time, you’ve had heating systems working with furnaces or old steam boilers. These older systems have flow channels of up to an inch in diameter, so they’re less susceptible to component failure as a result of iron oxide in the system.

When we moved to the more modern technology like condensing boilers — and, in particular, the ECM (electronically commutated motor) pump technology that will be compulsory by 2020 — it has caused a shift that all pump manufacturers are gearing up for. At this point, no matter what happens, it’s a done deal. So, it’s not the passing of that legislation that’s driving the market. It’s the fact the legislative review has already been done and, consequently, all of the manufacturers have changed to ECM technology to be ahead of that curve.

ECM pumps have a very low tolerance for magnetite. If the installer continues to install products the same way as he did before, he’ll encounter many callbacks due to system failures — not as a result of the products he’s installed, but as a result of failing to maintain system water quality.

There has also been a tendency to resort to some low-cost filter options, but they’re very ineffective. Where lower-cost products may have worked on older equipment that didn’t require the degree of operational excellence that new equipment requires, contractors will find these solutions increasingly ineffective. Installing a barrier filter — or much worse, no filter at all — will only result in more equipment failures.

Filter manufacturers such as ADEY are working on getting out the message to help educate the trade on these problems. We need to make the jump to get to the point where installing a high-quality magnetic filter is automatic. That’s the only way to maintain high-efficiency equipment, and to prevent system breakdowns.