the water dont flow into it fast enough to make it foam up lol would be funny though an its seems to be effective as it dilutes over time with it in traps as well and a little in bottom of case even smells lush lol when i did it in aldi stores managers would give ya a bottle for nowt off shelf saved them hasslee as well for a while ahh the supermarket days gettin soaked an stood on an moaned at how i dont miss it lmao another engineer used to swear by milton baby sterilizing tablets works great on smelly ac evaps never tried it on drains though they both good cos non toxic an pc touchy feely lol