Our GasClean filter for oxygen changes colour within a few days, so we've checked for leaks all up and down the lines but haven't found a leak. When we remove the filter from the connecting unit and pressurize the line, the pressure holds--but when we install a filter, the pressure releases (350 psi in 45 minutes). This is not normal is it? We purchased a new connecting unit and this one lost about 250 psi in 3 hours. I read elsewhere in this community that GasClean filters should be changed (in general) once a year. Are we installing it wrong? Or perhaps we need to be using another model?