Attached is the interior of my bathtub. The darker parts appear to be more like stains rather than dirt that can simply be washed off. What causes this and what do I need to do to clean it?
Just a couple cleaning sprays, like an all-purpose and a tub cleaner with a sponge. I was apprehensive to scrub really hard or use something stronger, so I thought I'd check here to see if that's all I need to do or if there's a different method I ought to use.
I may be wrong but that looks like rust stains to me from untreated water.
I'd get my water tested to see what type treatment is needed.
Your likely going to need to add a water softener.
You can clean all you want but if the waters not treated it will never end.
Whatever you use be careful mixing products. I know people try this and it doesn't work and then try that and the next thing they know they have a toxic gas coming up.
I have had good luck with laying paper towels flat on the stained areas, then wetting them with straight vinegar from a spray bottle.
Leave them on for a few hours, spray again if they are drying out, then clean up with a scotchbrite pad or similar plastic scrubbing pad.
Never mix bleach with ammonia. Also never mix bleach with acetone. Both will create toxic gas. They sell lemon scented bleach now for people who hate the bleach smell.
I have hard water (a lot of iron in my well water) so that staining in the tub looks familiar. The stuff coats everything my well water touches unless I run the water through a filter.