Pre-Commission Cleaning & Flushing

The Ultimate Guide To Pre-Commission Cleaning And Flushing

The pre-commission cleaning and flushing of pipework systems is a complex process.

With many procedures to follow, it’s of paramount importance that it’s carried out correctly.

That’s why we’ve written this guide to give you an overview of the topic.

This page covers:

• Why it’s necessary
• What happens if it isn’t carried out
• The standards that govern the process
• What to consider before you begin
• Assessing the water system
• How to ensure it’s a success

Why Pre-Commission Cleaning Is A Necessity

Pre-commission cleaning purges a pipework system of waste and debris. This includes biofilm, oil, and grease. Chemical cleaning and flushing leaves surfaces clean enough to apply a corrosion inhibitor. This helps prolong the life of the water system and ensure its optimal performance.

What Happens When Pre-Commission Cleaning Isn’t Carried Out.

If pre-commission cleaning isn’t carried out, there can be serious consequences. This is true for closed, open, hot water, and chilled systems.

A wide range of debris can accumulate in new closed water system installations. If these systems aren’t cleaned at the pre-handover stage, then this debris continues to build up. This gradually reduces the performance of the system and can lead to failure.

It can also cause erosion corrosion. This prevents the corrosion inhibitor from doing its job. Erosion corrosion can also be accelerated by chloride contained in some jointing compounds. Flushing the system with raw water won’t completely remove it. Only a thorough chemical clean utilising an appropriate biocide will be successful.

Other common issues include suspended solids, oil, and grease inside the pipework. These form a layer that the inhibitor cannot penetrate. More corrosion can occur as a result.

Hot water and chilled systems are particularly vulnerable to blockages. Strainers, small bore heat exchangers, and control valves are all common problem areas. Once a flushing and cleaning is project is complete, the water system will require continued treatment. This helps prevent further contamination.

The Pre-Commission Cleaning And Pipe Flushing Guidelines

Industry standard guidelines also make it clear that pre-commission cleaning and continued maintenance is essential.

BS 8552:2012 and BSRIA BG29/2012 are the standard regulatory guidelines to refer to.

There is also a BSRIA BG29/2020 version. It has a few additions relating to thin-walled carbon pipes and CPC procedures.

These guidelines take you through the entire pre-commission cleaning and flushing process. They also cover water sampling, and who is responsible for what.

Before You Begin

There are a lot of factors to consider and tasks to complete before you start. Here’s an overview of the most important ones, so that you’re informed ahead of time.


Pre-commission cleaning and flushing involves many steps, and these need careful planning.

A typical cleaning job will include:

• Pipework flushing
• Degreasing
• Circulation of chosen biocide
• Passivation
• Removing oxides
• Disposal via drains
• Dosing system with inhibitors

Because of the complexity of this process, keeping a record of all the details is crucial. Flushing velocity and water samples are two important examples. The samples should be taken from the whole system. This ensures the cleaning and flushing has been carried out thoroughly.

Pre-commission cleaning involves potentially harmful chemicals and specialist pipe flushing equipment. To adhere to all Health & Safety requirements, a risk assessment and method statement must be completed and signed off prior to carrying out any works.

If your installation is an older system, there are three further steps required:

1. There must be a clear reason why the cleaning is required
2. The pipe work should be examined to ensure they can withstand a chemical flush
3. The history of the system needs to be known

Before using any chemicals, it’s also important to know whether the system is suitable for them.

This means knowing:

• The system volume
• The debris within it
• The system type; open, closed, or partially closed.
• The materials pipes are made from; each material will require careful treatment and will react differently to each chemical.
• The scale within the systems pipe work; chillers, flow rate monitors, and small-bore control valves can be easily blocked
• If antifreeze is used and it’s glycol-based, this can nourish bacteria if not properly maintained
• Whether the system has been left as is since installation, or if it’s been modified in any way
• How long it took to build the system - this affects how much debris may have accumulated
• Data about how the system operates; the temperature, pressure, and flow rate will suggest the kind of treatment required.

Chemical Composition

There are many requirements to keep in mind when you’re selecting chemicals for the pre-commission cleaning.

The pre-commission cleaner used should be neutral in pH and high in polymer. It should also contain a surfactant and a chelant.

The neutral pH prevents metal from being damaged.

The polymer ensures solids and biofilm can be flushed out.

The surfactant removes any oil and grease, and the chelant dissolves corrosion.

The amount of chelant in a pre-commission cleaner determines its iron plateau level. BSRIA BG29 states 6ppm total iron and 3ppm soluble iron, but if the system is older, a lower level may be required.

Chemical Information

Biocides, effective inhibitors, and bio-dispersants are some types of chemicals required.

When you use these, you’ll need to consider the minimum contact time. If you’re using a biocide, then it should have a similar contact time to chemicals used in the pipe flushing procedure.

Maintaining the right concentration is also essential when using a biocide. Knowing the system volume will help with this.

The same calculation results and dosages should be used for three purposes. Calculating the system volume, the rates for the inhibitor, and the rates for any biocide you intend to use after the final flush.

The product should have a clear recommended dose so that the system can be tested easily. It will be difficult to choose how much of the pre-commission cleaner to use if it doesn’t. You can sometimes compensate for a lack of time with higher doses, but this isn’t always the case.

You’ll also need to ensure the product is supplied with environmental information. That helps dispose of it without any issues. Looking for one with low toxicity should help with this.

All this information helps ensure the chemicals are present for long enough to thoroughly clean the system.

Assessing The Systems Pipework

Once you’ve completed the paperwork and researched the required pipe flushing chemicals, you’ll need to physically inspect the pipework.

Several factors need to be assessed. These are:

• Water quality
• Drainage facilities
• Pumps
• Power supply
• System integrity

There needs to be enough water available for the pre-commission cleaning and flushing. A double-check non-return valve needs to be fitted as well.

Taking samples of water before beginning the flushing works is recommended, so that you can test its quality. As stated previously, you should take samples from the whole system frequently, and they should be taken both pre-flush and post-flush.

If there are any issues with water quality, the water can be treated with biocide as it enters the pipe work.

The water system should be pressure tested and filled before work begins. This ensures its integrity. You should also fit bypasses near valves as needed, place the units on bypass, as and leave the main valves fully open. This will keep any debris away from the units.

A waste licence to use local drainage facilities will be required. That’s because the wastewater will be full of chemicals. As well as securing a licence, the drains used should be able to tolerate the volume of water you intend to pour down it. Keeping a record of where drains are on-site is also required before work commences.

Some older systems can have a high level of scale, and this is often most noticeable on heat exchangers. The best way to deal with scale is to dissolve it, rather than applying acid. Systems with large amounts of scale will need a specialist product.

Pumping the water is a necessity, and this requires power. You should ensure that the power supply you use is stable, as well as having a backup to rely on, like a generator.

Calculations should be made to ensure the pumps can handle the pipe flushing velocity. You may need to add more pumps, but if you do, use isolation valves to reduce the risk of short-circuiting.

Ensuring Pre-Commission Cleaning And Flushing Is A Success

If you follow all the guidance given above, then you should have no issues with the process. There’re only a few reasons why the cleaning process can fail, and here they are:

• Stagnation
• Lack of data
• Presence of oxygen
• Untreated water
• Excess refilling
• Failing to improve water quality

This is why carefully selecting chemicals, completing the paperwork, and assessing the system are such important steps.

Once the cleaning is completed, you can take samples to see how much bacteria is present and what the pressure level is. It’s important not to top up the water because this could put bacteria back into the system.

Water systems can change quickly, and close attention needs to be paid to what’s going on. This includes before, during, and after cleaning. That way any issues can be spotted before they become too serious.

What’s Next…

Now that you know all the above, you might think there’s a lot to keep in mind. And you’d be right. Each system has its own requirements and will need a unique approach.

The most efficient way to carry out these specialist works is to seek advice from trusted experts.

That’s why we offer specialist pre-commission cleaning and flushing services. We can cover everything that’s been outlined in this guide while saving you time and giving you peace of mind.

To find out more, speak to a member of our team by calling 0800 772 0628, or fill out the form below.

UK Tank Relining Company

Nationwide Service Coverage

Our head office is based in Kent and we have specialist teams operating from London, Kent, Berkshire, Southampton, Manchester, Newcastle, Glasgow & Edinburgh ready to provide you and your clients with the services that you require.

Echo Square has an enviable reputation for carrying out successful projects of all sizes across a wide range of industry sectors from NHS hospital sites and factories to schools and residential properties.

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