TSP, or Trisodium Phosphate, is one of the most powerful cleaning agents still in regular use. It's especially good at cleaning greasy buildup off tough surfaces, like flooring or siding, but it can be dangerous to work with, and can damage sensitive materials.
Safety Note: TSP can cause injuries if it comes in contact with eyes or skin. Always wear protective gloves and goggles when working with this substance and never ingest it. Wash any areas of accidental skin contact thoroughly with soap and water, and flush any eyes it contacts with water for at least 15 minutes.
Benefits of TSP
Properly applied with a brush or spray, TSP can help you prepare tough surfaces for repainting or refinishing, and can clean off mold, mildew and fungal growth when combined with household bleach.
Because it's so corrosive, you should only use TSP on resilient materials like stone or brick, or on surfaces you're planning to repaint after cleaning. It makes an effective substitute for muriatic acid, another potentially hazardous substance.
A good starting ratio is half a cup of TSP dissolved in two gallons of warm water. For a more powerful solution to combat mildew and mold, you can dissolve one cup of TSP in three quarts of warm water and add one quart of fresh chlorine bleach.
Disadvantages of TSP
TSP is also dangerous for plants and wildlife, and environmental campaigners have raised concerns about introducing phosphates into ecological systems through runoff into local water sources. If you're concerned about these impacts, you can substitute borax for many cleaning tasks you might be thinking about tackling with TSP.
TSP can also harm the items you're trying to clean. It's not a good match for delicate fixtures, as it can stain the metals of your faucets and pipes, and damage glass showers and ceramic tiles. Its high alkalinity can react with aluminum, causing corrosion and releasing hydrogen gas.
As it does with paints, TSP can even attack and remove grout, and in fact it's often used in products that help take off old grout and glazing.
The bottom line is that this cleaner can be extremely effective for getting your home in tiptop shape, but it can do more harm than good if you don't know how to use it.