This instructable not so funny but practicable, the U-tube of the ground level drainage may not filled with water, you may sometimes filled the bad smell, and the professionals stated that empty U-tube may distribute diseases. There are seldom times that plenty of water will flow from the ground drainage except if the water closets in trouble, so you might need to take caution to fill the U-tube periodically.
Many designs of the ground drainage have a filter grid, so you think hard how to fill water in, this instructable is done in no cost, you need a pet bottle with the lid, a RCA plug sleeve, a plastic tube from the form bath bottle and some glue, that is.
Step 1: The Funnel
Cut the bottom of the pet bottle in what ever length, drill a hold in the lid to plug in the RCA plug sleeve, just the sleeve not the plug, glue well. pull out the plastic tube from the empty form bath pump head, insert the plastic tube the sleeve and glue too, bend the tube over the stove slightly right angled, crimp flat the tube tip can go through the filter grid.
Step 2: Fill With Water
Plug the tip into the grid, hold the funnel upright and pour half liter of water into.