The appeal of the Shark line of cleaners, vacuums and steamers is the use of steam for sanitizing rather than harsh chemicals that can cause a toxic environment in your home. In light of this, the water canister is not designed to use anything other than water. Adding any kind of chemical, soap or even essential oils to the canister can damage and even ruin the steamer, causing it to no longer work properly.
Even the water you use in your Shark steamer must be chosen carefully. If you have hard water, identified by a mineral buildup of calcium or lime around your water fixtures and in your sinks, toilets and tubs, do not use tap water in the steamer. The hard water will leave mineral deposits inside the steamer, just as it does on your faucets, causing corrosion and blockages within the unit. Instead, use distilled water in your steamer.
To keep your Shark steamer and steam cleaners in good working order, empty any remaining water out of the canister after each use then rinse the canister thoroughly to remove any dirt or sediment that can gradually build up and clog the hose.
Always unplug any steamer unit when adding to or emptying the water reservoir. Failure to do so can result in electrical shock. Be sure the cord and plug are completely dry before plugging the steamer back in. When operating the steamer, be aware that steam from the diffuser can burn you so do not touch the diffuser anywhere but on the handle while the steamer is hot.