Picture the scene, wet patch on bathroom floor by toilet (it's not what you think) DH thinks there's a leak, he thinks it might be an underfloor pipe for the radiator. 
I try explaining that on the 1st floor of a building water does not leak up. He doesn't get it and insists it must be a pipe under the boards.
He says we meaning me need to check the garage.
Now I know for a fact that there is no leak in the garage as I checked yesterday paranoia because our bath leaked last year
So I went into the bathroom and pulled up the carpet so see where else was wet. Behind the toilet. So whilst I'm on the floor I flush to toilet and discover what is leaking.
So I tell DH exactly what the problem is.
He is still going on about a pipe under the floorboards that must be leaking.
aibu to be thoroughly exasperated with him because he doesn't seem able to grasp the concept that Water doesn't leak up! especially in a house where gravity is firmly established
if it helps I'm pregnant and I'm sure he's not usually this aaaahhh