You can even fill a ziplock bag and tie it on a faucet.
If your water is really hard, pour vinegar into that little tube in your toilet too, the jets get clogged easily and that flushes them out and prevents them from blocking up. If they are blocked, the vinegar will eventually open them up if you don't regularly.
Obviously water softener if you don't have one, but depending what your waters like you may have to do more.
An alternative to vinegar is citric acid. You can buy it as a tub of crystals so it's much cheaper because you aren't paying for water. It's great because you can add more teaspoons to water to make it stronger than vinegar. Plus it doesn't smell bad like vinegar.
Where do you find citric acid? I've been using white vinegar in a jar in my dishwasher which gets rid of all water spots and cleans better with my hard water. However, I'd like to find a place to purchase citric acid crystals without relying on Amazon.
Citric acid is commonly used in the canning process. So look in the canning section of the grocery store. The last time I found it was at an ACE hardware that had a very good canning section.
Oxalic acid is an option for rust removal, but it is less common. Basically you need an acid that is safe for fiberglass tubs but works on rust. I have also used stuff like CLR or Lime-Away. Just double check that they are safe for the tub.
Just remember that even weak acids can be dangerous to work with. Wear gloves, eye protection and make sure the room is well vented.
Almost any store that sells general canning / food preservation supplies will have food grade citric acid crystals. If you're in a part of the world that has Walmart, Target, etc, then those types of places will usually have it. Grocery stores often have it. Sometimes it's considered a seasonal item and is only stocked during times of the year when people are doing lots of canning (i.e. spring through fall).
I think if you sprinkle a little baking soda in there that could help with some of the more stubborn stains but vinegar alone works really well. I recently cleaned all the hard water stains off my sliding glass shower door with it.
