You can smell damp. You either decide to lift up the carpet or you don't.
As soon as you choose to lift up the carpet, you know the floor beneath is wet.
Then it's a question of whether you keep lifting up the carpet towards the downstairs toilet.
Having seen the wet floor, you can decide to either put the carpet down, knowing that there's damp beneath, or you can keep going.
Keep lifting, keep looking. Or stop and bury the knowledge; live with damp.
You keep lifting the carpet. Halfway to the bathroom, you're looking at obvious piss and shit. The question then becomes, "How much accumulated old piss and shit can I stomach, because it's not going to lessen under the remaining half of the carpet?".
So you can still put the carpet down, or you can face the horror of the backed up toilet that you, your family and every person who ever went into that toilet shat in.
Then the question becomes, "Did anyone top-deck the downstairs toilet?".
Turns out, they did. Your father-in-law. Awks.
UK Government reports suggest the Fully Vaccinated are rapidly developing Acquired Immunodeficiency Syndrome, and the Immune System decline has now begun in Children
Dr. Jessica Rose: the impact on your immune system (US VAERS data perspective)
Update: