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.

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 leave the surface clean enough to apply a corrosion inhibitor. This procedure helps prolong the life of the LTHW or chilled water system and ensures its optimal performance.

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

If pre-commission cleaning isn’t carried out, there can be severe consequences. This applies to 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, 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 altogether remove it. Only a thorough chemical cleaning utilising an appropriate biocide will be successful.

Common issues include suspended solids, oil, and grease inside the pipework. These form a layer that the inhibitor cannot penetrate. Advanced 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 common problem areas. The water system will require continued treatment once a flushing and cleaning project is complete. This helps prevent further contamination.

The Pre-Commission Cleaning And Pipe Flushing Guidelines

Industry-standard guidelines also clarify that pre-commission cleaning and continued maintenance are essential. BS 8552:2012 and BSRIA BG29/2012 are the standard regulatory guidelines.

There is also a BSRIA BG29/2021 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 you’re informed beforehand.


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

A typical system flushing project will include the following:

  • Pipework flushing
  • Degreasing
  • Circulation of chosen biocide
  • Passivation
  • Removing oxides
  • Disposal via drains
  • A 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 work.

Flushing Older LTHW And Chilled Water Systems

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 pipework should be examined to ensure that it 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 suits them.

This means knowing:

  • The system volume
  • The debris within it
  • The system type; open, closed, or partially closed.
  • The pipes are made from; each material requires careful treatment, and reacts 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 pre-commission cleaning. Pre-commission cleaners used should be neutral in pH and high in polymer. They should also contain a surfactant and a chelant.

It’s critical the cleaning chemical utilised has a neutral pH, as this prevents the metals in the system from being damaged. The polymer ensures solids and biofilm can be flushed out, whereas the surfactant removes any oil and grease, and the chelant dissolves the corrosion within the system.

The amount of chelant in a pre-commission cleaner determines its iron plateau level. BSRIA BG29/2021 states 6ppm total iron and 3ppm soluble iron, but a lower level may be required if the system is older.

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, it should have a similar contact time to the 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. Calculate 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 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 true.

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 long enough to clean the system thoroughly.

Assessing The Systems Pipework

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

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 to test its quality. As stated previously, you should take samples from the whole system frequently, which 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.

before and after flushing samples

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, 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 large scale level, which is often most noticeable on heat exchangers. The best way to deal with scale is to dissolve it rather than apply the 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 your power supply is stable and have 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 above, you should have no issues with the process. They’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 important.

Once the cleaning is completed, you can take samples to see how much bacteria is present and the pressure level. 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 must be paid to what’s happening. This includes before, during, and after cleaning. That way any issues can be spotted before they become too serious.

Require help with a Pre commission Cleaning and Flushing project?

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

The most efficient way to do 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 learn more, speak to a team member by calling 0800 772 0628, or contact us here.

Who We've Worked With

James Eckloff
James Eckloff
We used Echo Square services to reline a water tank in a local school recently, fantastic work and completed within the timescales needed
Gaetano milazzo
Gaetano milazzo
Had a cold water tank in the loft full of dust, wasp and flies. Tanks were cleaned to a very good standard, considering the awkwardness of the job. Very happy with the service
Stuart Mills
Stuart Mills
We were carrying out plumbing works on a site in London where we discovered a badly leaking GRP water tank, the Echo Square Services team attended site as quickly as possible to repair the leak and reline the tank. We will definitely contact them next time we are faced with a similar issue - would highly recommend.
Daniel Sheen
Daniel Sheen
We had a heavily leaking metal water tank above our office which was leaking through our ceiling, Echo Square Services repaired the leak and relined the tank just two days after we made the enquiry!
Harold Carter
Harold Carter
Arrived very quickly when the crisis developed in the 100-year-old water tanks in this Grade 1 listed building; did what looks a highly professional job (re-lining two hard to get at tanks in the roof) all in one day - which involved working really late - and were careful to make no mess and cause no damage. So far, it looks a great job at a reasonable cost.
Stuart Mills
Stuart Mills
I have used Nationwide Tank Relining on two occasions now and each time I have been absolutely delighted with their service, ‘can do’ attitude and professionalism from start to finish. I will definitely be requesting their services again in the future.
Luke Busby
Luke Busby
Working with James was a pleasure, thanks again bud will be in touch for my next project
I contacted ECHOSquare to reline our water tank due to it being damaged and developing a leak, we needed the job doing ASAP as our site had no water so staff had to be sent home until it was fixed, James understood how urgent the job was and he was i spoke with him on the Friday and he was able to get the job booked in for the Monday, all The necessary Paper work, IE Rams & Training Certificates were sent to me via email before the guys got to site, from start to finish the service was excellent, Thanks ECHOSquare.
Dark Iron Fabrications
Dark Iron Fabrications
The team was very helpful, polite and knowledgeable. Glad to speak to people who know what they're doing. Won't hesitate to use them again in the future
Rachel Pickett
Rachel Pickett
Having used other companies in the past I can wholeheartedly say that our dealings with Nationwide Tank Relining have been a breath of fresh air. We have had tanks relined, water hygiene assessments and floor coatings. All work was carried out in a timely manner and the quality of work has each and every time been exemplary. My bosses are thrilled with my decision to switch to Nationwide Tank Relining and a tank that was relined 10 years ago by them still looks good as new internally, and the money we've saved from choosing the right supplier has proven to be a very smart business move. Highly recommended!

Buy With Confidence

The quality of our product combined with our skilled team of applicators means we can offer a comprehensive guarantee of up to 15 years (10 year minimum guarantee).

You can rest assured that Echo Square will provide the very best service from start to finish and emergency backup should you ever need it.

Enquire Today