Hot water boilers and steam boilers alike need a water source. This can either be city water or well water supplied by a pump. This is the source for water that is fed into the boiler. Barring any leaks, drips, or weeping in your system, the supply from the well or city is necessary to keep the water level up in the boiler. A dry fired boiler is very dangerous and it is important to keep the water in the boiler at proper levels. For hot water boiler systems the boiler should be full. Steam systems are different. Too much water and the boiler mains flood. The steam boiler will not function properly with flooded mains. A boiler control at the supply should keep the proper water levels in the system. The beginning of the supply (city or well) should have a gate or ball valve to turn the water off to the boiler for maintenance and/or to stop major leaks. When this is shut off the power and fuel source for the boiler should be shut down also. After the shut off valve there should be a back flow preventer, however there may be some older boilers that do not have back flow preventer's. Current local and national codes require back flow preventer's to keep the boiler supply water from being contaminated by back flow water from the boiler. Older boilers are grand fathered so they do not require a back flow preventer. After the back flow preventer there should be a pressure reducer valve (PRV). Many city water sources (and well sources) have pressures exceeding 40 P.S.I. A residential boiler should not operate at pressures over 20 P.S.I. The pressure reducer valve reduces the supply water pressure down to 12 P.S.I. After the pressure reducer, the boiler source supply water for the boiler should be fed into the boiler return or boiler supply loop.

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