Сухой трап из 50 мм стандартного трапа.

thingiverse

The problem of drying out the standard trap and smelling is familiar to many. After re-examining different structures, I came up with this solution. When the water dries out, the opening is closed, and when there is water, it works like a siphon. The usage time is more than 3 months, the flight is normal, and previously the smell appeared within three days. The lower layers of the model (upper when used) need to be made 100% full filling, which I did not do, so I had to impregnate with epoxy to prevent water from entering the float. There is one peculiarity - it does not like sudden releases of water (when a lot of water is poured at once) - compresses and closes the opening. The water pressure exceeds the buoyant force of the float. You need to either lift or wait for the water to drain itself. The standard trap grate rises, the plastic cover is removed and replaced with this float.