A closed recirculating system is one in which the water is recirculated in a closed loop without evaporation or exposure to atmosphere.  Very little make-up water is needed in these systems unlike cooling towers and boilers, so they are typically thought of as very easy to treat.  Unfortunately, for that same reason, they are also easy to overlook and attention can be limited until of course a failure occurs.  In this section we focus on some ideas for closed system treatment.  A couple of those ideas include…1) Cleaning your loop for restoring efficiency and 2)Filtration for improved maintenance.