Good morning, I am looking for a 500-n-125a-tp manual for a unit but, it is not in your website equip. model list. the problem we are having is that; during high water usage there is a water leak between the water tank and the fire box. weekends no leaks. the gasket seems to be ok. is there someplace elsa I should check? maybe the water is jumping over samewhere! advise please. I appreciate it guys