sewer gas smell

I have read your archives and don’t see anything that fits my problem. I have a 1 ½ story house served by a septic tank. The house was finished 2.5 years ago. The home has bad sewer odor from time to time. Downstairs only never upstairs. I just determined that the odors may come when it is windy.

Someone else lived in the house until I moved in a few months ago. They complained about sewer odors from the downstairs bathrooms. The odor is much worse in the master bath. I took off the master toilet and replaced the gasket and re caulked around the toilet after I replaced it. The new seal did not help. While the toilet was off, sewage smelling air was forcefully coming out of the toilet hole, like a fan was behind it. All the toilets and sinks are used frequently so I know the traps are full, (if they exist). The builder went broke so I can’t call him. The roof vents have a cap over the pipes to keep rain out. The attics don’t stink and the odor comes and goes so I don’t think there is a pipe leak. My email is [email protected]. Phone is 512-217-3398.

Oh yea I almost forgot, the water level in the low flow toilets is very low all the time. Maybe it’s so low that the toilet trap isn’t submerged. Can the water level be raised somehow?