An apparatus comprising: a recirculating water system comprising a recirculating water system inlet, and a recirculating water system outlet, a chemical feed system comprising a chemical feed system inlet and a chemical feed system outlet, said chemical feed system inlet connected to said recirculating water system outlet, and said chemical feed system outlet connected to said recirculating water system; said chemical feed system further comprising a storage tank having a storage tank inlet and a storage tank outlet and a chemical feed tank having a chemical feed tank water inlet, a chemical feed tank water outlet, and an opening for receiving solid chemical, said chemical feed tank configured to receive through said opening solid chemicals which include an indicator-chemical and to allow said solid chemicals to dissolve or partially dissolve in water held in the tank; the storage tank inlet connected to said chemical feed system inlet via a first piping having a first isolation valve, and said storage tank outlet connected to said chemical feed tank water inlet via a second piping having a second isolation valve; said chemical feed tank water outlet connected to said recirculating water system via a third piping including said chemical feed system outlet, a chemical feed system isolation valve and said recirculating water system inlet; said storage tank located at a lower elevation than said chemical feed tank so that said storage tank is gravity fed with contents of said chemical feed tank when said first storage tank isolation valve is closed, said second storage tank isolation valve is opened, and said chemical feed system isolation valve is closed, during loading of solid chemical into said chemical feed tank; a measuring device for measuring the level of the indicator-chemical in the recirculating water system, an automatic valve to allow dissolved chemical held in the chemical feed tank to flow into the recirculating water system based on a measured level of said indicator chemical. a recirculating water system comprising a recirculating water system inlet, and a recirculating water system outlet, a chemical feed system comprising a chemical feed system inlet and a chemical feed system outlet, said chemical feed system inlet connected to said recirculating water system outlet, and said chemical feed system outlet connected to said recirculating water system; said chemical feed system further comprising a storage tank having a storage tank inlet and a storage tank outlet and a chemical feed tank having a chemical feed tank water inlet, a chemical feed tank water outlet, and an opening for receiving solid chemical, said chemical feed tank configured to receive through said opening solid chemicals which include an indicator-chemical and to allow said solid chemicals to dissolve or partially dissolve in water held in the tank; the storage tank inlet connected to said chemical feed system inlet via a first piping having a first isolation valve, and said storage tank outlet connected to said chemical feed tank water inlet via a second piping having a second isolation valve; said chemical feed tank water outlet connected to said recirculating water system via a third piping including said chemical feed system outlet, a chemical feed system isolation valve and said recirculating water system inlet; said storage tank located at a lower elevation than said chemical feed tank so that said storage tank is gravity fed with contents of said chemical feed tank when said first storage tank isolation valve is closed, said second storage tank isolation valve is opened, and said chemical feed system isolation valve is closed, during loading of solid chemical into said chemical feed tank; a measuring device for measuring the level of the indicator-chemical in the recirculating water system, an automatic valve to allow dissolved chemical held in the chemical feed tank to flow into the recirculating water system based on a measured level of said indicator chemical.