How Often Does This Happen?
You don’t have to worry about evaporation occurring in the event of a weekend getaway or even a short business trip. In general, P-traps remain sealed for at least a couple of weeks, possibly even longer. However, in extreme circumstances, P-traps can dry up faster.
Extreme heat, dry environments, high levels of ventilation and/or air flow, and basement floor drains, laundry room standpipes and spare bathrooms tend to lose their water seal faster.
In most cases, this problem arises during longer trips, typically three weeks or more, or in areas of your home where the drain rarely receives water.
Does the “Paper & Upside-Down Glass” Trick Really Work?
While we should give credit to those who came up with this hack, there’s a logical premise behind it. If you cover a drain, it may slow down the rate of evaporation, and potentially block odors or insects from entering your home if the P-trap dries out. Therefore, the theory behind this hack is valid.
However, the implementation is where things fall apart.
Unless the upside-down glass creates a tight seal over the drain opening, it’s unlikely to do much of anything. Simply resting the upside-down glass in the sink basin is merely decorative. Additionally, the paper will likely become soggy and unsightly from moisture in the air, and will not form a true seal.
In fact, any slight jolt to the sink could dislodge the entire setup.
