Closed System Cleanliness

How often should the water treatment in a commercial closed system be monitored?

For a newly constructed and well-maintained systems that have been correctly pre-commission cleaned and treated the answer is simple; once every six months as a minimum…… assuming no water has been lost through leaks or maintenance work. A loss of water means a loss of chemical protection and checking no later than once every six months generally allows for remedial work to be arranged before the system degrades too far. But, as so often is the case, the water treatment is neglected or forgotten.

But with systems not so well constructed or which have an inherent water loss, such as older systems that have been poorly maintained, where the system is often devoid or low on inhibitor concentration, it is not even worth considering having the system routinely monitored.

Low or non-existent levels of corrosion inhibitor results in progressive degradation of the system metals to cause oxidation, particularly in mixed metal systems where the sacrificial metal is the ferrous content. In such circumstances the system monitoring is not even worth considering until appropriate remedial action is undertaken to restore the system to a good internal condition.

Oxides deposit in areas of low flow and can cause cold areas within radiators and blockages of pipework. The introduction of an inhibitor can mobilise some of the deposits, but not all, so systems may need chemical cleaning prior to the inhibitor introduction. Regrettably, some blockages are so severe that even the strongest cleansers are ineffective, meaning some heat emitters or terminal units have to be removed for manual cleaning. Once the system has undergone a restoration clean to an acceptable standard, the system chemical concentration can be monitored every six months.

However, leaking systems will allow fresh water rich in dissolved solids and oxygen into the circuit to cause further problems. The oxygen will be a further cause of corrosion and the dissolved solids in areas of hard water will present a scale problem.  The system must be made sound and the leaks stopped, after which it should be cleaned to a reasonable standard and correctly treated before routine monitoring can be considered.

Before restoration cleaningAfter cleaning


The image to the right is that of a strainer taken from a commercial heating system that had not been pre-commission cleaned, had leaking components and has been without water treatment for just twelve months.



The image to the left is the same strainer after the system had been subjected to a restoration clean……….the difference is striking and the efficiency of the system transformed. The clean also led to improved pump performance and decreased wear.


If you need any advice on the treatment of closed systems, please contact us on 020 8659 1833. Hints and tips on system cleaning can be found in various publications, such as BSRIA’s application guide BG/29.

By | 2015-03-26T15:32:06+00:00 March 26th, 2015|Aldous & Stamp|Comments Off on Closed System Cleanliness

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