Closed System Water Treatment

Pre-commission Cleaning

Closed System Water Treatment (Pre-commission Cleaning)

Closed System Water Treatment cleaning in relation to heating, cooling and other closed pipework systems is the process of bringing the water system to a satisfactory condition for commissioning and ongoing maintenance of water quality.

System contaminants such as mill scale, jointing compounds and building debris will unavoidably be found in newly made-up heating and cooling pipework systems. If these materials are left and are allowed to build up over time these contaminants will make the system prone to blockages. These blockages usually begin at strainers, control valves and small bore heat exchangers. Further corrosion of the pipes is likely and this will eventually encourage the growth of micro-organisms such as Legionella.

The necessity of Closed System Water Treatment in recent years has certainly increased and this is due to modern day heating and cooling systems moving towards energy efficient control strategies that result in low flow rates in terminal units with consequently very small orifices in control valves.

Pre-commission Cleaning

Do I need a Closed System Water Treatment?

If any of the following cases apply to you please speak to a member of the team today to discuss a Pre-commission Clean.
– Have you had a new installation of a heating or chilled closed water system?
– Have you had a large scale extensions or alterations to a water system?
– Do you conduct regular water sampling (which will determine preventative or remedial action) and need advice on results which need action but you are not sure what to do?
– Has your water system shown a decline in water quality (e.g. increased iron levels)? This can often specify potential corrosion activity and needs addressing.

Pre-commission Cleaning BSRIA Guide


All of our works are carried out in accordance with:
• BSRIA BG29/2012
• BSRIA BG50/2013
• BS8552


What is the process of a Closed System Water Treatment?

Closed System Water Treatment is achieved through a process of flushing and chemical cleaning. (where necessary), followed by the addition of biocides and inhibitors

How do you know if a Closed System Water Treatment was successful?

As it is not possible to directly examine all of the internal surfaces of the water system, the success of a Closed System Water Treatment is determined by taking water samples, which are then analysed for a range of parameters including suspended solids, iron and bacteria.
Once Water Hygiene Services has undertaken a Closed System Water Treatment, your water system should;
1. Be free of debris and dirt.
2. Internal surfaces should be free of millscale and will be appropriately treated to minimise ongoing corrosion.
3. Pipework, fittings and terminal units should be free from settled solids, which could increase the risk of corrosion.
4. Residuals levels of solids should be low enough not to cause difficulties with commissioning or significant accumulation in low flow areas.
5. Bio film formation should be minimised by appropriate use of biocides and those bacteria associated with microbiologically induced corrosion should be controlled.

Water Hygiene Services prides itself on the highly experienced in-house Engineers who are trained in working with all types of water systems. When conducting a Closed System Water Treatment job our team ensure they work within a management framework and ensure safe and effective working practices whilst ensuring record keeping is documented through each stage of the process. You will be supplied with a full report post Closed System Water Treatment, which will detail the process we took, the results and recommendations for future maintenance.

Pre-scommission Cleaning

For more information on a Closed System Water Treatment or to discuss your job please contact a member of the Water Hygiene Services team.

Please look at the other services we offer.


Phone: 0113 267 9785

Very happy with their very high standard of work Water Hygiene Services have been carrying out legionella risk assessments for us for a couple of years now. We have been very happy with their very high standard of work, their ability to work to tight deadlines and the general professional service they provide

Richard Waudby
Engineering Surveyor, NPS Humber Ltd