Q1 - If the house and water has not been used in months, the junk in the pipes may have made the water quality much worse. Run the water for hours (outside dump).
Water gets ran regularly, I just replaced the entire system with PEX line from the pressure tank out. Sample was taken from a spicket directly off the pressure tank, there is a 4 way split, in /out, one in to tank, then spikot out the front. Entier system has pretty much been flushed in the last 2 weeks.
Q2 - Contact the local 'Extension Agent" or "Building Inspection Office" to see if this is a common problem in your area, they can look at Soil Maps, elevations & soil types and water quality/levels in your area on their maps.
My sister is in college taking some ecology lcasses, she found out there has been wells going "sour' due to a bad flood in 2003 or 2004. This well was dug in 1992 and had hard, but not slaty water. I thikn the saltiness caem bfore the flood, but not sure. It went bad pretty quick though.
Q3 - Talk with close neighbors, to see if they have had this, and what they did.
The only neighbor did have a Culligan system so she could use it, but did not have this level of salt in hers, she just had iron and hardness.
• How close is the sewage field, trash dump, animals. Water comes from an 'aquafier' which can pick up junk from great distances, it does tend to run or flow in a direction? What's upstream (the Soil Maps will show this)?
• One of our continued problems is 'Nitrates' from local farms, it's in the aquafier for years to come, so all of us around here have to "shock" our well yearly with Chlorine & run the well for at lest 8 hours, dumping water, we still can't use this water to bath babies or drink, but it's OK for bathing and washing. We use an osmosis for drinking and cooking. To save a lot of salt, buy an "on-demand" water softner, in our case, we use about 1/4th of the salt we used to (just 25%, or 50#/month).
Good luck, and let us know how you come out.
We do have a large river and some tributaries within 1000-1500 feet maybe along with about a 1000 acre active corn/bean farm on the other side of that. Water was checked last year for nitrates/arsenic/coloforms, all came back at 0 levels. Mom used to shock the well yearly, it will help the saltiness a tad, but then come right back. It is recomended now not to shock them with chlorine anymore. Chlorine is not an issue for me other than if shocked. I know you have to remove if using RO with city water.
Water softeners remove calcium and magnesium ions from the water. .....The brine wash (salt) strips the calcium & magnesium from the resin bed in the softener, and replaces them with sodium ions.
That's one of the problems we have if using standard iron filter then a softener, we would still have a super high amount of sodium in the water after softening, this causes the "harsh" water which then is as bad or worst on going through a RO system afterwards. The softener uses the salt to clean the resin beds and adds low amounts of salt into water, I would be cleaning resin bed all the time LOL
From my research and what I was recommended, I will need a large almost commercial size RO system to do everything with probably at least a 200-300 gal reserve tank with a pump, then I would need a mineral tank afterwards to replace some of the good minerals. Drawback is excessive use of water, the large storage tank and costs. I orginally had about a $1400 system setup using small RO for drinking lined out, but this high salt content really screws that up.
It's overall really wierd, mom's neighbor ( within 250 ft up rooad) doesn't have this big of an issue and I live 1/4 mileby the crow flies around the corner and I have great water using a softener, my water is hard, but no rust and my softener regenerates every 3 days with family of 4. We have city water, but most of my neighbors are all on wells and no issues i know off other than slightly hard stuff. Even mom's old well had rusty/hard water, but this salty thing seems to be a thing of it's own.
I'm at 2 water tests and recommendations, may call someone else and get a third opinion.