Xaviera Arata Editor of the Cheap Hot Tubs website -- http://www.CheapHotTubs.me -- pointed out;
“…A clean cover will keep a clean tub. Get a garden hose and spray the water on the surface of the cover. Do so until the debris and the dirt come off…” Added Xaviera Arata
Get a soft brush and a large sponge to scrub on the spa cover. Do it with a mixture of dishwashing liquid and water. The vinyl top should be scrubbed in a circular motion and don't let it dry with the soap! Rinse it well with water. As for the underside of the cover, wash it with water and dry with a rag.
Never, let the soap get into your hot tub! It will be a lot of trouble if it happens since you have to get it out of the tub.
Remedies for unwanted dirt
Anything can get on your spa cover such as tree sap, paint, grease, or grime, especially when your hot tub is under a tree or in your backyard. Tree sap can be annoyingly hard to get off, but a little bit of lighter fluid will do the trick. Don't use too much because it will damage the vinyl cover. Right after the application of the fluid, apply your preferred spa cover conditioner or soap.
As for paint - sorry, but there's no way to get it off. Once it dries, it remains there forever. Yes, there are solvents used to remove paint, but its a different story once you apply it on the spa vinyl cover. Solvents used to remove paint can damage your vinyl cover permanently.
Damages, blisters and whatnot
Sometimes fading color, blisters, or puddles show up on your spa cover. When the bottom vinyl of the spa cover sags like blisters, it means the water chemistry of your tub water is off. Improper water chemistry may manifest on your spa cover by color change, its being easily ripped, or falling into the water. The best remedy for this is to replace your spa cover.
“…These are just some tips on how to protect your spa cover. Treat your spa cover with care to make it last for a long time. It saves money and it saves a heck of a lot of worry…” Added Xaviera Arata
Further information, resources and reviews of the best but reasonable priced hot tubs by clicking: http://www.CheapHotTubs.me