You already answered your question…you find little to no value in the bathroom as it is, but would find more value if it was utilized as proper storage. Don’t try to second guess what some imagined person in the future might find valuable.

Is your property large enough that a future occupant might get pretty dirty working in the yard, so that they might want to take a shower to clean up before traipsing through the rest of the house? Just because you don't use this shower doesn't mean a future occupant won't. Do you think you might sell sometime in the near future? Have you spoken to realtors in your area to get their opinion?

The builder added this bath as an after thought. They built my street and owned a construction company. I’m sure this was useful to them.

For me, the toilet and sink is nice. But is this worth having to jackhammer the slab up? Also, what’s the life span of copper plumbing?

I plan on living here indefinitely. At least the next 20 years.

Including pics of the plumbing and how it runs thru basement wall under slab. I’m concerned because it’s looking iffy.

Explain what you think is iffy. All I can see in the photos is that the copper is tarnished and the sweat soldering is a little sloppy, but looks adequate.

The “iffy” part is that I’m concerned about what the condition of the pipes may be inside the slab. They’re about 40 year old copper pipes and I live in Ohio. I’ve been told by one plumber that copper starts to fail around 50 years. I’m unsure what the cost to repair or replace copper pipes in concrete would be.

Also want to point out that the pipes are going to be going thru cold and warm seasons. I’m a bit nervous about the sweating of the pipes causing issues with corrosion that I can’t see.

I agree with Kilroy. Are the copper pipes actually embedded in the concrete, or do they simply pass through it with clearance provided by a sleeve? And as for "sweating" by itself causing corrosion, that's a non-issue.

The pipes are running thru a 4 to 6 inch piece of PVC tubing. No sleeves.

If you want to remodel the bath into a half bath plus additional storage go ahead, you know how the house works. I can’t imagine a full bath off a kitchen adds much value anyhow. I would not arbitrarily do it because the pipes might fail. Your furnace might fail, your electric might fail, you have lead paint… it’s a 70 year old house. If those pipes do fail turn them off and problem solved.

I agree with @HALLETT & Co. You’ve said a couple times that the toilet / sink is useful to you & guests. Think about taking out shower & converting the space to a toilet room and a room for freezer & more kitchen storage. Worth exploring possibilities. If you post a floorplan with all wall measurements & doors, windows etc. my bet is you’ll get way too much advice on how to lay it out!

"It makes sense to me not to deal with the future nightmare of having the floor jackhammered up to repair pipes and remove it."

Who says the floor would have to be jackhammered? They may supply through the attic in a day with no dust.

I understand that you would appreciate the storage space, but the possibilities for the full bath are also great. If you ever need a live-in helper, the garage and bathroom could be made into their own suite. Or an in-law suite as someone else mentioned. As a gardener, I would appreciate the shower. So would anyone with kids playing in the yard, or if a pool (even a kiddy one) was put in for the summer. Or for dog showers.

I would not worry a bit about the copper pipe going bad, Copper is the mainstay and other than having to replace it after thieves strip an empty house, I have never heard of it having to be replaced. What is the shower like? Is it big enough and square enough for shelving inside of it? If so, use it that way. Can you do a drawing of the kitchen, breezeway, and bathroom and surrounding rooms with measurements and doors and windows marked? Folks here love to re-arrange and find space for peoples’ projects. Pictures help, too.

You can always wait to demo the bathroom when the pipes break.

I'd be tempted to see if it can be reconfigured as a powder room with room left for the storage you need, but I don't have any idea what size and shape space you have.