As of right now, If SHTF I don't have a BOL. I will be sheltering in place. A concern crossed my mind and I don't know if it has any validity. If the public sewage system were to fail due to power outages, could the sewer system conceivably back up enough that it would start overflowing in a house? I know it probably is a function of where you are in the 'altitude' of the system so to speak. But I was wondering if it may be worthwhile to have a packer/plug that could be installed in the toilets and sinks to make sure your BOL doesn't become un-inhabitable. By the time this may happen, sure you would have a mess, but could the mess of just cleaning a couple bathrooms and kitchen turn into 2 feet of sewage throughout a whole house?