Common sense: Had removed a WC from my yard toilet three years ago. Now it smells!

[Cecil Lee]

If the WC sewerage drain pipe is not properly capped, this can occur.

As often the contractor merely places a plastic membrane sheet and covered by a tile.

Once the “u-trap” no longer hold liquid, by osmosis, the sewer smell may slowly seep out of this tile. Thus causing the stench.

The disadvantage of capping is the floor may have to be raised to accommodate this plug.