Methane gas smell or cloudy water is usually caused by algae blooms, decaying organics in shallow wells near swamps or oil well fields, or housing areas built above old landfills where the decaying organics have penetrated the water source / aquifer. Methane gas is explosive and toxic to breathe, making treatment of this issue vital. If you notice a methane smell in your water, do not use the water until it has been treated by a water professional. This problem can be resolved with a well vent or an open-aeration system (that provides proper venting of this methane gas to prevent explosion) which is then re-pumped up to proper pressure levels.