related articles: article index to toilet information Or use the search BOX found below to Ask a Question or Search InspectApedia. Question: whooshing sound air boosted toilet flush sources 2016/09/10 Richard Baldwin said: Hope you can help. Details are at toilet fill valve Bowl shapes of toilets There are two basic toilet bowl profiles or shapes, round (which are not necessarily exactly round - illustrated at below left where a Church toilet seat is installed and elongated or more of a flattened. The flush control for this tankless back-flush toilet is that round button just above the toilet tissue holder. See details about power-assisted flush or pressure-assist flush toilets at LOW water usage toilets. Back-flush toilet, aback-flush toilet (illustrated and explained in the article below) is designed to flush horizontally out of the lower back of the bowl into a waste pipe that is mounted in the wall behind the unit. The compressed air is what forces the water into the bowl, so instead of the pulling or siphon action of a gravity unit, the pressure-assist unit pushes waste out. A traditional back-flush toilet is designed to work by gravity alone.