Suction cups allow you to add storage space to tiled walls such as the shower without drilling holes or using adhesives. If either the suction cups or the tiles aren't clean, however, the cups won't stick for long, if at all. Even after a thorough cleaning of both the suction cups and the tile, the cups may fall off. Water, cooking oil or petroleum jelly help keep the suction cups in place with enough gripping power to hold items such as shower caddies.
Treating the Tile
Suction cups stick best to smooth, slick surfaces. Soap scum, mineral deposits or even water spots on the tile walls may hinder the cups' ability to stick. Wipe the tile down with a household cleaner or tile cleaner appropriate for your tile; then rinse the cleaner away. Afterwards, wipe down the area again with rubbing alcohol and a sponge or durable cloth. Alcohol helps cut through any remaining grime or debris that may prevent sufficient suction. Even if the tile walls are completely clean, suction cups will not stick to heavily textured tiles or extremely porous tiles, as they require a perfect seal in order to stay put.
Soap for Better Suction Power
Whether the suction cups are brand new or have been used before, give them a thorough washing in warm, soapy water to help remove dust or greasy films that may prevent them from sticking to the tile. Pat the suction cups dry with a paper towel afterwards. The underside area -- the portion that sticks to the tile -- is the portion that must be clean and free of dust.
Wet the underside area of each suction cup in warm running water, shaking off excess water; do not pat them dry, as the small amount of remaining moisture helps them stick to the tile. Press each cup in place along the tile in a desired location. For an item with two or more suction cups, such as a caddy or soap dish, hold the item up near the tile to ensure it is straight or aligned as desired before pressing the cups onto the wall. If the suction cups feature separate hooks so you can hang various items from them, allow the cups to stick to the tile for a full day before hanging anything from them.
Super Suction Tips
Sometimes, moisture alone isn't enough to create sufficient suction. Lubricate the the underside of each suction cup just inside its perimeter with a small amount of petroleum jelly or cooking oil; then press each cup onto the tile in the desired location. Over time, the suction cups may lift away from the tile slightly. If so, press them toward the tile to burp out the excess air.