Water Quality in Heating Systems | Thoroughflush

Water Quality in Heating Systems | Thoroughflush

In this episode of Energy Unwrapped, I’m joined by Ricky Prescott from Thoroughflush to talk about one of the most overlooked parts of any heating system: water quality. Whether you have a boiler or a heat pump, the water moving around your radiators and pipework has a huge effect on reliability, efficiency and long-term performance.

We get into sludge, filters, flushing, inhibitors, VDI, system monitoring and why so many homeowners never think about any of this until something goes wrong. Ricky makes the case that poor water quality is behind a huge number of breakdowns, and that a lot of those problems could be avoided with better commissioning, testing and ongoing care.

A big theme throughout the episode is simple: people often spend thousands on a boiler or heat pump, then pay almost no attention to the water running through it. That lack of care can cause blocked strainers, damaged components, corrosion, poor flow rates and repeat faults that should never have happened in the first place.

What we cover in this episode

• why water quality in heating systems matters more than most homeowners realise

• how sludge and debris damage boilers and heat pumps

• why flushing a system properly is so important

• what magnetic filters and line strainers actually do

• the risks of poor commissioning and chemical guesswork

• why inhibitor needs to be measured, not just poured in

• what VDI water treatment means in practice

• chemical vs chemical-free heating system treatment

• why heat pumps can be especially sensitive to blocked strainers and poor flow

• the signs that your heating system water may need attention

Watch or Listen

Spotify: https://open.spotify.com/episode/628vkfB4VoIxeNPGhL4KSa?si=LOuGsRLWR_WgUSLlX0dETg

Apple Podcasts: https://podcasts.apple.com/nz/podcast/water-quality-in-heating-systems-what-homeowners-must/id1875873044?i=1000754816775

Watch on YouTube

Full Transcript

Below is the full transcript for this episode, lightly edited for readability.

Why Water Quality Matters in Heating Systems

At the heart of this episode is a simple point that many homeowners never really think about. Your boiler or heat pump is only one part of the system. The water flowing through every radiator, valve and pipe is just as important. If that water is dirty, chemically unbalanced or carrying sludge and debris, it can slowly damage the very components you are relying on to keep the house warm.

Why So Many Heating Systems Are Full of Sludge

Ricky explains that one of the biggest problems in the industry is that many systems are simply not flushed properly. Debris, black sludge and corrosion products stay in the system, settle in radiators and then get stirred back up later. Homeowners may never see that happening, but the evidence often shows up in magnetic filters, blocked strainers and failing parts.

Heating System Filters, Magnetic Filters and Strainers Explained

We spend time talking through the different jobs of magnetic filters and strainers. A magnetic filter can catch ferrous sludge, while a strainer helps stop larger debris getting into sensitive components. For heat pumps in particular, protecting the plate heat exchanger and maintaining good flow rate is critical. This is why filtration is not just a nice extra. It is basic system protection.

Why Flushing a Heating System Properly Matters

A major message from Ricky is that flushing is still not happening often enough. Whether an engineer uses a dedicated flushing tool, a power flush machine or even a very simple method, doing something is usually better than doing nothing. The real risk is fitting an expensive new appliance onto old dirty system water and hoping for the best.

Why Inhibitor Needs Testing, Not Guesswork

One of the more eye-opening parts of the conversation is around inhibitor. Many people assume inhibitor is just something you pour into the system and forget about. Ricky explains why that is a bad habit. Different products use different chemistry, not all can be tested in the same way, and overdosing a system can cause its own problems. The right dose matters, and the only sensible way to know where you are is to test.

Chemical Soup, Mixing Products and Unknown System Water

We also talk about the problem of mixing chemicals over time. If one engineer adds one product and another later adds something different without knowing what is already there, you can end up with what Ricky calls a kind of chemical soup. That is a good example of why records, labelling and proper monitoring matter. If nobody knows what is in the system, good decisions become much harder.

What VDI Water Treatment Means

This episode also gets into VDI water treatment, which comes from German engineering guidance on heating system water quality. In simple terms, the idea is to reduce the conditions that allow corrosion and scale to happen, rather than relying only on chemicals. That can include demineralised fill water, conductivity testing, pH checks and keeping oxygen out of the system as much as possible.

Why Oxygen Is the Real Problem

A line that really stands out in this episode is Ricky’s point that oxygen is the killer. Once oxygen keeps getting into the system, corrosion has the conditions it needs. That is why sealed systems, stable pressure, good commissioning and avoiding repeated top-ups all matter so much. It is not just about what goes into the system once. It is about keeping the whole thing stable over time.

Why Repeated Top-Ups Can Damage a Heating System

Another useful section focuses on pressure loss and topping systems up. Many homeowners treat topping up as normal, but repeated top-ups can keep introducing fresh water, oxygen and hardness into the system. In hard water areas, that can bring scale problems too. If you are having to top up regularly, that is usually a sign something needs attention rather than just more water.

Why Heat Pumps Can Be More Sensitive to Water Problems

We also discuss why heat pumps can be especially sensitive to water quality issues. Boilers can often seem more forgiving, while heat pumps tend to rely on tighter flow conditions and more delicate internals. A partially blocked line strainer can have a noticeable effect on flow rate, performance and faulting. That makes proper flushing, filtration and monitoring even more important for heat pump owners.

The Importance of Monitoring Heating System Water Over Time

A recurring theme in the episode is that commissioning is only the start. Good water quality is something to monitor over time. Conductivity, pH, iron levels and inhibitor levels can all help indicate whether the system is stable or if something is starting to go wrong. That gives the installer a chance to intervene early before a homeowner ends up with blocked parts or bigger failures.

What Homeowners Should Ask Their Installer

By the end of the episode, the homeowner advice is pretty clear. Ask how the system will be flushed. Ask what filteration is being fitted. Ask what chemicals or treatment method are being used. Ask whether the water is being tested and recorded at commissioning and at service visits. Those questions are simple, but they can reveal a lot about how seriously the installer takes water quality.

About the Energy Unwrapped Podcast

Energy Unwrapped is my podcast about renewables, home electrification and how energy technology works in the real world. You can browse all episodes, platform links and future updates on the main Energy Unwrapped Podcast page.

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