A brief explanation of a BSRIA BG29/2012 flush and why they are so important

A brief explanation of a BSRIA BG29/2012 flush and why they are so important

DATE:
10/07/2019

A BSRIA flush is a term often thrown about and requested, but rarely fully understood. In fact, when most people ask for a BSRIA flush, they get just a regular system flush - they just don’t know they’ve been short-changed. 

It’s easy to see why everyone is so confused about what a BSRIA flush is. You have to obtain a guide from BSRIA BG29/2012 to get the full details.

When to specify a BSRIA flush

The BSRIA guidance document BG29/2012 is for new pipework systems, not for remedial cleaning or flushing. If you are specifying a BSRIA flush on existing pipework systems, you may expect the service provider to follow the recommendations and methodology defined in BG29/2012, but there are several criteria that would not be relevant or even achievable. This is why good engineering judgement is required when carrying out remedial cleaning or flushing of existing pipework systems. You need someone experienced and someone you can trust.

A BSRIA flush explained

Think of the BSRIA flush as a Big Mac, and you’ve just paid for this Big Mac and parted ways with your hard-earned cash, only you get to the collection point and you’re given a 99p cheeseburger. However, you don’t know it’s just a 99p cheeseburger so, you eat it and it’s okay. That doesn’t mean there’s anything wrong with a 99p cheeseburger, it’s just not what you paid for.

McDonald’s themed analogies aside, in truth, BSRIA flushes are far more complex than a regular flush. It involves taking and trending microbiological samples of the incoming water quality that are going to be used to fill & flush the system with, rather than just crack on and use water with unknown microbiological content.

However, with greater complexity comes increased procedure time, and inevitably, greater cost. This greater cost is justified (but that’s only if you get what you paid for) as regular flush would take around 48 hour using 24 hour cleaner contact time, whereas a BSRIA BG29/2012 flush can take up to two and a half weeks from start to finish.

So what does a BSRIA flush entail?

A complete BSRIA flush carried out to BG29/2012 guidance would include full test results of the stages and processes carried out, in broad stroke terms these are some of the process stages that are followed such as the achieved flushing velocities and iron plateaux during the chemical cleaning. 

And as such therefore carefully documented records should be available to the water system owner and form part of the handover documentation along with operation and maintenance manuals, in a form of a comprehensive report compiling the various measurements and results obtained instead of one page certificate. If additional cleaning is undergone as the BG29/2012 guidance, the associated water test results and chemical dosage will have to be included. 

For example, in a closed water system comprising of main plant air handling units and office layout with 250 fan coil units, we would carry out an initial water change and prove the system levels are equal to mains quality. This is often referred to as static & initial dynamic flushing.

For systems classed as being “at risk of bacteria” this process would be followed by a biocide wash, possibly for three to five days which is dependant on the timeline between first fill and start of cleaning. Water is less likely to be circulated and been treated with biocides for long lasting periods of time, the risk of microbiological growth increases as the time passes, and therefore the needs of a biowash is more necessary. It is essential to ensure biocide has entered and is present at all extremes of the system (including any coils that have been wetted) this is done with the use of chemical tracers and by field testing the biocide concentration. 

Procedures to follow would be chemical cleaning and then “batching” with recording, witnessing and documenting flushing velocities to ensure any particles of are removed, one propensity of the cleaner is that it has the ability to suspend particles in solution. Post chemical cleaning the system will be dosed with suitable inhibitors & biocides and then enter a seven day passivation period, this is to achieve stability and uniformity in the system .

At the end of this passivation period, the system will be sampled bi-weekly and trended, daily circulation must be maintained all prior to PC (practical completion). Post PC BSRIA BG50/2013 Water Treatment for Closed Heating and Cooling Systems becomes applicable and that’s a different blog.    

There are installation requirements needed to ensure a successful outcome, for example, drain cock sizes. The general rule of thumb is drain cock sizes should be equal to the pipe size up to 50mm. Particulate matter, in suspension, will never be flushed through a small drain cock with the dynamic volume required. There is an importance of having flushing by-passes and isolation of sensitive items of plant such small bore control valves, fan coil units, heat exchangers, air handling unit coils, boilers and chillers.

But why get a BSRIA flush if it’s so much more expensive?

Normal flushes are perfectly fine in most scenarios. However, sometimes a regular flush is not enough. Generally, BSRIA flushes are required on specification and focus on bacterial biocide washing along with full documentation of the processes and stages for future auditing.

Flushing to BSRIA BG29/2012 standards are not necessarily carried out on some projects for various reasons, the simple fact is that you won’t know whether it’s been performed correctly or not which is why independent stage witnessing becomes so important, the potential problems the BSRIA flush are meant to prevent do not materialise immediately, or if they do, the systems are re-flushed straight away, and the problem is solved albeit temporarily specially when sessile & planktonic bacteria are involved.

BSRIA flushes are essentially a long term solution - as the procedure is so in-depth and complex as it focuses on prevention rather than treatment.

Why does this matter?

Ensuring people are educated on BSRIA flushes is important, as it allows the customer to hold water treatment businesses to account, particularly if all parties involved know the BSRIA flush stages.

This would have a knock-on effect, raising industry standards across the board and allowing us to build trust with our customers, as they know we are executing what they ordered as best we can - because they know and understand what they asked for.

A BSRIA flush is a term often thrown about, specified and requested, but rarely fully understood. In fact, when most people ask for a BSRIA flush, they get just a regular system flush - they just don’t know they’ve been short-changed. This is why it is essential to correctly specify what deliverables are to be provided on completion and to review them for completeness. In doubt refer to BSRIA guide BG29/2012 or get in contact with us here at Comfort Services Group for further assistance or advice.

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