How do I get the black lines out of hardwood floors without replacing?

Here's a tutorial on how to refinish your hardwood floors. You'd need to sand and re-seal the floor, but it's doable: https://www.hgtv.com/design/real-estate/how-to-refinish-hardwood-floors

sand and reseal - takes some elbow grease, but it can be done!

I would think that you could get most of it out with a good sanding. When we bought our latest house, we had the whole house redone. They sanded, stained then put three coats of Bona commercial urethane on it. That was four years ago and they still look the day they were done.

Now that you're motivated, you need to refinish as Beth has suggested. It probably needs to be smoothed, anyway, since it has been rather abused over the past 18 years. You'll need to sand - go from a low number grit to a high number in steps and at that point you can decide if you want to re-stain the floor. Fill in any big empty spots with wood filler (knowing it will take the stain a bit darker). Make sure the floor is completely free of debris (including dust and dog fur) before you seal it. We used a nice satin polyurethane on our floor. Oh, and make sure you remove wall accents and hang some drop cloths on furniture in all doorways before you start sanding. It will save you HOURS of dealing with the dust. If you don't have a sander, you might want to check some YouTube videos to help you choose what will work best. Take your time and I'm sure you'll love the result.

Before doing anything I would give them a good wash with Murphy's Oil Soap and see how they turn out. If that doesn't do it, then I would consider having them refinished.

You'll need to sand the floor down, restain, and refinish it.

Sorry to say but, I think they would need to be sanded, stained an sealed. I do have two professional flooring guys I can see what they say if you like. I'll check back to see if you want me to.

Growing up we had hardwood floors way before they were "in style". Back then men's shoes seemed to always leave black marks on the floor. Mom had us us a dry steel wool to remove them prior to dry mopping and then a go over with Murphy's Oil Soap. Try that prior to refinishing.

Before undertaking a refinish job, I would TRY two great products. 1) Magic erasers, slightly damp and wrung out, probably the extra strength ones. They do a surprisingly good job on things like kitchen sink, bathroom cleaning, etc. And might work on your floor. 2) Tuff Stuff, an excellent cleaner from Walmart or a car-parts store. Comes in a tall yellow can. You could spray some on a folded paper towel to test. Test on the most hidden area first. OR if it is just a small area, you might cover with two low-pile carpet squares with that good tough black non-slip backing.

It looks like the marks are from a worn finish. If so, you will need to either screen and recoat or refinish completely. If you have not used any wax or oil products on it (including Murphy's oil soap) sometimes you can screen and recoat vs sand and refinish. If they were prefinished floors to begin with vs. site finished they may need to be sanded. I personally would not use magic erasers. I have damaged my floor finish trying to take off a few small scuffs.

Before you commit to refinishing, try this. Put some lemon oil on the area. Work it in with a nylon scrub brush wipe with a clean dry cloth. Repeat until it is clean. Give it a good wipe with the dry cloth and if necessary cover it with a throw rug for a couple of days, then go back and wipe it with a dry cloth to get rid of any oil the wood didn't absorb. I suggest you avoid cleaning with anything that is waterbased because water can turn unsealed oak black. Once you get it clean you can seal the floor with floor wax.

Of it's just in spots, try soaking a rag with peroxide and letting it sit on the stain. Worked for me.

Please people I beseech you not to use Murphy's oil soap, Orange glow ,or any products containing oil, wax, or silicone. If your floors have been done in the last 30 years it more than likely has some type of polyurethane finish. These products are considered contaminants and can get into the micro pores of wood. When recoated or sanded and finished even down to bare wood the above products can cause modern finishes to separate and peak. Call a professional, 75% of the time we can clean and buff the floor and recoat it the the Bona recoat system. If the floor is worn too badly it will require a refinish. I train my guys for years before they are allowed to do either of these things by themselves. For most homeowners this is a task left for a pro. Even among professional floor companies a cheap job with 3 coat of polyurethane may last 2-4 years, whereas a good company with the right products and techniques can take three coats and make a floor that will last 10-20 years. (You get what you pay for) The picture you put up is just dirt embedded into the grain and will sand out. I am Joe with Joe's hardwood floors Inc. San Diego, CA. this is our 30th year in business and my company has sanded well over a million square feet of flooring and have fixed homeowners attempts at refinishing many times. Do yourself a favor and call a pro he can get you in the right direction.

Joseph, Thank you for your valued n experienced comment. May I ask you what I should look for in finding a contractor?

Thanking you advance,

Linda

Here are several tips and tricks that might help you https://chascrazycreations.com/floor-cleaning-hacks/

Sand the stains away and then seal the floors. i know it is a lot of work but well worth a beautiful floor.