I arrived today to check over the tankless install, and to address a potential drain issue. The homeowner made me aware that the union at the bottom of the tankless unit was loose, and he had to tighten it to prevent the gas from leaking. However no other gas smell was present after he addressed the loose union. I used leak detection fluid to verify that other gas leaks were present, I sprayed all fittings we installed and no leaks were presented. They also made me aware of a drain issue they experienced Saturday after they returned. The drains were gurgling, which the issue has not persisted since then and it seemed to be a single occurrence. I made them aware that a soft stoppage may have been present, but has cleared itself since then. They also experienced a sulfur smell during this occurrence, which is explained by sewer gases. They’re going to treat their drains and fixture traps with hydrogen peroxide to treat the bacteria. If the issue should reoccur or persist, we can return t