A neighbor recently tiled our 2 bathrooms and replaced the toilets (using one new toilet and one old toilet). About a week after he completed the job we started having a terrible stench in the master bath - BUT it does not stink around the toilets - it stinks through the air conditioning/heating vents (but not the vent closest to the toilet). The guest bath is now also starting to stink. At first we thought it was the sink/bath drains that do not get used that often. We ran water in all drains but the smell has not gone away. My husband and neighbor went under the house and there are no signs of a leak under the house.

They also checked the drain vents under the sinks (that do not appear to vent to the outside). The pipes have a cap on them with a small slit at the top - they were not familiar with this type of venting system.

Any help would be appreciated.