Purchase trisodium phosphate.
Where can I purchase trisodium phosphate to treat a mold problem on my back deck?
Many paint stores and hardware stores carry TSP. If unavailable in your area you can look online. Painters-Toys.com carries <a href="//www.painters-toys.com/dap-trisodium-phosphate.html" target="_blank">Trisodium Phosphate by Dap</a> in a couple of different sizes.