FLUSHING & CLEANING | Monitoring after Flushing

December 20, 2022 |

Once the flushing and cleaning activities have been completed, including the backflushing, there will usually be a delay until the handover as other commissioning works will need to be completed, such as hydraulic water balancing.

During this delay, the responsibility of maintaining the System, and the water quality, will be the general/main contractors or any specialist they have employed.

The works and requirements are pretty straightforward forward which we run through below.

Why monitor the quality?

It is imperative to complete this stage as it will ensure the System is handed to the building owner/facilities team in line with the specification and there are no problems, which could cause delays to the process and additional costs.

The worst case of allowing the water quality to deteriorate is that parts of the flushing process will need to be completed again; it could also affect the operation of the plant and equipment.

To see our full example of a method statement for the Flushing & Chemical Cleaning works, including the ongoing monitoring click here
Flushing & Chemical Cleaning Method Statement [MS Word]

Here is our Open Copy of our Flushing and Chemical Cleaning Method Statement in MS Word. With instructions




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Monitoring plan

A ‘Monitoring Plan’ should be put in place to ensure the correct steps are taken. Usually, this will form part of the method statement.

Agreement of the plan

Once written, the plan should be agreed upon with the following parties:

  • System Chemical Engineer.
  • Commissioning Manager.
  • Designer.
  • Building Operator/Facilities Engineer.

Items the plan should cover

The following should be identified in the plan:

  • Who will be responsible for the sampling and analysis.
  • Quanitiy of samples to be taken and locations.
  • Time between samples.
  • If site analysis and laboratory analysis or just laboratory.
  • Water quality parameters for reviewing the results.

Responsibility for the activities

The below provides an overview of activities and tasks that will need to be completed with examples of who would achieve them.

RefActivity/TaskResponsible
1Writing of the monitoring planGeneral / Main Contractor / Contractor / Chemical Specialist
2Approving the monitoring planChemical Specialist / Commissioning Manager / Designer / Building Owner
3Implementing the monitoring planGeneral / Main Contractor / Contractor / Chemical Specialist
4Overseeing implementationCommissioning Manager
5Sampling and providing laboratory certificatesGeneral / Main Contractor / Contractor / Chemical Specialist
6Analysis of result to understand if there are issuesGeneral / Main Contractor / Contractor / Chemical Specialist
7Final reports before handover of the SystemGeneral / Main Contractor / Contractor / Chemical Specialist
8Approving reportsCommissioning Manager / Designer / Building Owner

Quantity of samples to be taken and locations

The quantity of water sampling should be conducted in line with the following, which is covered in more detail in our article ‘DYNAMIC FLUSHING | Procedure & Sequence’.

Size of SystemQuantity of SamplesWhere to SampleTime between Samples
<3,000 Liters and <2 Terminal UnitsOneOne in Main Plant Area every 2 weeks
<3,000 Liters and <25 Terminal UnitsThreeOne in Main Plant Area + Two in Remote Locations on the Systemevery 2 weeks
<8,000 Liters or 25 to 80 Terminal UnitsFourOne in Main Plant Area + Three Remote Locations on the Systemevery 2 weeks
<20,000 Liters or 80 to 250 Terminal UnitsFiveOne in Main Plant Area + Four Remote Locations on the Systemevery 2 weeks
<40,000 Liters or 250 to 500 Terminal UnitsSixOne in Main Plant Area + Five Remote Locations on the Systemevery 2 weeks
>40,000 Liters or >500 Terminal UnitsVariousOne in Main Plant Area + [no. of terminal units/500]x5*every 2 weeks

Tools and equipment that can be used

The following tools, systems, and equipment can be used to provide information on the System:

  • Site water analizing kit – for quick onsite understanding of the water quality.
  • Sampling bottles – for collection of water.
  • Chemical treatment system – to ensure the water within the pipework is dosed inline with the specification.
  • Corrosion coupons, where installed – to help understand the corrosive nature of the system.

Monitoring parameters

The water quality parameters would be dependant upon the specification of the System, type of materials, and requirements of the designer/chemical specialist.

Usually, the parameters analyzed would be:

  • Suspended Solids
  • Conductivity
  • pH
  • Total Alkalinity
  • Total Hardness
  • Nitrates
  • Sulfates
  • Chlorides
  • Total Iron
  • Dissolved Iron
  • Total Copper
  • Molybdate
  • Phosphates
  • Glycol
  • Total Viable Count [TVC]
  • Pseudomonas

What to do if any issues are noted?

Once the analysis and reporting of the samples has been conducted, there needs to be an evaluation to ensure the results are inline with expectations, or if thre are any issues such as the parameters rising over time.

Where any issues are noted, the chemical specialist should be notified straight away. They will then complete further investigations and make recommendations as the the steps that need to be taken.


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