Contaminated Closed Loop Recirculating Systems

Closed recirculating loops generally utilize little make-up and should rarely become exposed to bacteria.  In theory, closed recirculating loops should not foul easily. However, due to the repeated isolation of zones and exchangers during change over seasons and re-exposure of water into a dual temperature systems, stagnation and fouling are a major concern in closed recirculating loops.  Mud, accumulated in dead leg and low flow areas, further perpetuates fouling by serving as a nutrient source.  This also gives an ideal breeding ground and shelter to bacteria.  Most treatments do not permeate the layers of mud therefore do not effect or protect dead leg and low flow areas areas.

Improperly laying-up exchangers creates stagnant water that is ideal for the propagation of bacteria and accelerated corrosion.  When a stagnant body of water is reintroduced to the bulk water, contamination occurs and bacteria proliferate throughout the entire system in a relatively short period of time. Your current vendor should be aware of this, and should be taking certain measures to sequester and/or obstruct the progress of corrosion and bacteria.

As mentioned above, zones of stagnant water will contaminate all areas of a closed loop.  An effective program will maintain the optimum conditions for a healthy system by taking the necessary measures to both prevent and eliminate fouling.  If Purity’s cleanout and lay-up program is followed every changeover season the effects of these contaminants should be successfully reduced.

The make-up water/ expansion tank can be an additional source of bacterial contamination.  Often they are open to the air (atmospheric) and will contribute to the bacterial fouling of the recirculating loop.  An aggressive sanitizing and blowdown program will help maintain an excellent pretreatment hygiene.

If a glycol (antifreeze) is being used to winterize fan coils, it is ideal to flush and chemically cleans each coil’s waterside before active service begins.  Glycol can foul a system and cause various problems if not flushed properly.  Noxious odors, low pH, and corrosion of metal surfaces are some of the detriments that it creates. Bacteria feed off the depleted glycol and metabolize it for basic nutrients.

Please refrain the use of nitrite based inhibitors.  Nitrite is easily metabolized by certain bacteria and will contribute to their proliferation.  As a water treatment vendor, we will not utilize a nitrite program in any dual temperature loop.

If you have noticed a foul odor or slime accumulations from your closed loops please contact Purity Labs immediately which will enable us to assess and correct the situation.