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Power Flush vs Chemical Flush


As your heating system advances in age, it will start to run into problems resulting from the buildup of debris in the system. With the efficiency of the central heating system lowered, you may begin to think about acquiring a new boiler. There is no need for such thoughts, though. With a single power flush or chemical flush, you can easily remove sludge, dirt, and debris from the system, thus improving its efficiency.

Besides boosting the efficiency of your boiler and central heating system, flushing will also increase their lifespan and prevent future breakdowns.

However, how can you tell when your system needs a power flush and when it needs a simple chemical flush?

No need to guess. In this guide, we will talk about the features of both types of flushing and signs that your system needs either kind of flushing.

What is a power flush?

A power flush is the deep cleaning of your heating system and boiler by flushing hot water and a combination of chemicals through the system at high pressure and high flow rate. The cocktail of chemicals dissolves the dirt, sludge, and debris built up in the system, which is then suspended and transported by the hot water.

All heating systems typically consist of metal components, be it the pipework or the boiler. The metallic parts corrode over time, leading to the accumulation of rust and debris in your central heating system. The accumulation of the sludge in the system will block water from running freely through the heat exchanger, hence lowering the heating system’s efficiency.

A power flush dislodges and removes any accumulated sludge, rust, and debris from your system, thus improving the efficiency and lifespan of your heating system. It will also prevent future breakdowns resulting from blockages due to the accumulation of the same.

How is power flush done?

During a power flush, a powerful pumping unit is attached to the central heating system. The pumping unit is then turned on, and it circulates water containing the cleaning chemicals in both directions. After flushing the whole system in both directions for about 90 minutes, the focus is shifted to the contaminated radiators.

The radiators are worked on separately by flushing for about 15 minutes in both directions. If the sludge buildup is significant, an agitator in the form of a touchpad attached to a hammer action drill is used to scour the radiator.

Once the system is cleared, a chemical neutraliser is introduced and washed through the system. The chemical neutraliser cancels out the acidity introduced by the cleaning chemicals, leading to internal corrosion.

Lastly, an inhibitor fluid is added to the system to prevent corrosion and sludge buildup.

When does my system need a power flush?

Typically speaking, a power flush is only needed when your central heating system is heavily contaminated by dirt, rust or sludge, thus lowering its efficiency. Since this is not an everyday occurrence, it suffices to say that your system doesn’t need frequent power flushing.

In fact, if you strictly stick to your annual heating system servicing plan, you’ll only need to do a power flush once every five or six years. However, the time between power flushes may vary depending on the type of boiler, its age, and the system you have.

Another factor that influences the frequency of performing a power flush is the material of the heat exchanger. If your boiler uses stainless steel heat exchangers, then there is no need to worry as it doesn’t rust easily. On the other hand, if your boiler uses copper heat exchangers, you may need to perform a power flush sooner as it has a high corrosion rate.

Your five or six-year grace period may not even elapse before you find your system needing another power flush. The tell-tale signs that indicate your system need a power flush may include:

  • Your central heating taking longer than usual to heat up
  • Discoloured water coming out of the radiators when you bleed them
  • Cold spots mainly at the bottom of your radiators
  • The boiler constantly shutting down and needing to be restarted
  • Radiators requiring constant bleeding
  • Some radiators don’t heat as well as the others
  • Unusual noises coming out of your radiators or boiler
  • Your pipes are hot, yet the radiators are cold
  • Cloudy tap water indicating a limescale buildup

Also, note that you usually recommend a power flush when installing a new boiler to clear the system and ensure optimum performance.  Otherwise, you risk contaminating your new boiler with dirty water and debris, especially if your existing system is ancient.

Some boiler manufacturers also require you to perform a power flush before installing the new boiler. Failure to do so will render your warranty void.

Who should perform a power flush?

As no rules restrict who can carry out a power flush, it might be tempting to have a crack at it yourself or hire a cheap street tradesman for the task. However, this is not recommended, and it is best to leave it to a professional Gas Safe engineer.

The process requires specialised chemicals, which might pose a risk when handled by untrained hands. A mistake could also occur during the process, leaving the system in a worse state than before, and you may end up calling an engineer anyway.

The engineer may also discover and solve some underlying issues in your central heating system when performing the power flush.

Some manufacturers also require the process to be handled by a certified engineer; otherwise, your warranty will be voided.

How long does a power flush take? 

Your house will be without hot water or central heating when a power flush is being done on the system. Understandably, you would want to know how long the process typically takes to make preparations beforehand.

Well, the time it will take the engineer to complete the power flush will vary depending on your system’s size, age, and condition. On average, the process can be completed in about eight hours. However, if the issues in your heating system are pretty severe, it may take up to two days for the power flush to be completed

Benefits of a power flush                

The number one benefit of a power flush is increased system efficiency as it removes radiator sludge, boiler limescale, and other contaminants in your heating system.

It also boosts your heating system’s lifespan by preventing corrosion, rusting, and blockages.

Other benefits of a power flush include:

  • Enhanced energy efficiency leading to lower energy costs
  • The reduced likeliness of boiler breakdown
  • Quieter boilers and radiators
  • Improved quality of central heating and hot water
  • Restore pressure in the system
  • Improve system reliability

What is a chemical flush?

A chemical flush or a hot-and-cold flush is the process of clearing rust and blockages from your central heating system by introducing chemicals into the system and allowing it to circulate in the system.

How is a chemical flush done?

A chemical flush is a simpler version of a power flush that requires no installation of pumping units. Cleaning chemicals are simply introduced at the boiler and left to flow naturally in the system.

As the chemicals pass through the heating system, they disperse, suspend, and remove accumulated debris, dirt and rust and transport them. The dissolved materials are then emptied by gravity at several outlets in the system.

Once the cleaning chemicals are out of the system, a chemical inhibitor is introduced, and then the system is flushed with clean water.

When does my system need a chemical flush?

As earlier said, a chemical flush is a more basic form of power flushing. It is no surprise then to know that the signs of your system needing a chemical flush are pretty similar to those mentioned under power flushing. However, they should be on a smaller scale.

For instance, if you notice that only one or two radiators are developing cold spots or your system takes slightly longer to heat up, a chemical flush will be enough to fix it.

Also, if you recently did a power flush, it would be uneconomical to go for a second round when you suspect your system may have accumulated sludge.  In such a situation, performing a chemical flush will be enough to remove the little sludge accumulation in the system.

Lastly, it is recommended that you do a chemical flush of your system whenever you install a new central heating pipe system, radiator, or even boiler. Chemically flushing your system at this point will remove debris from the installation process and prevent the latest additions from being contaminated.

Who should perform a chemical flush?

Given the simplicity of the process, you can perform a chemical flush of your heating system on your own without engaging the services of an engineer. All you have to do is acquire the necessary chemicals, introduce them into the system, and you’ll be good to go in no time at all.

Benefits of a chemical flush

The benefits of a chemical flush are somewhat similar to those of a power flush. However, their extent is limited as the process is not as thorough as the latter.

All in all, performing a chemical flush will clear the built-up debris in your central heating system, thus boosting the efficiency of your heating system.  By removing rust and scale buildup in your system, a chemical flush will also increase the lifespan of your boiler and eliminate unnecessary breakdowns.

Also, by cleansing blockages in your radiators, a chemical flush will allow hot water to reach the cold spots in your radiators.

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