[Gavik]

We have a well water system and soda ash tank. I went to add soda ash today and found that water is backing up and flowing back into the soda ash tank (or at least to the pump). When I turned the pressure release valve (that usually only pumps out a few drops to get the soda ash flowing) water was spewing out like a garden hose. The pump was unplugged, so it's definitely not coming from the soda ash container, but rather from the house pipes.

I have no idea what this is. Is is a pressure tank problem? Should I just drain the backed up water? Will it even stop? Ideas?

Also, water pressure in the house is fine. Aside from acidic water due to lack of soda ash, there are no other changes to the water.

 

[Gavik]

When was the last time that you cleaned the point where soda ash is injected to the water stream?

Soda ash will build up at the point of injection and needs to be cleaned every so often so that the injection can continue.

Not for a long time, but we did the best we could today. Couldn't clean the tube that delivers the soda ash to the rest of the water since water was spewing out through that. But I did notice soda ash built up just after the pump on top of the soda ash tub.

 

[Gavik]

If there is any way of removing the part and letting it soak in vinegar for a few hours that would help.
You might also take the line from the pump to the injection point and do the same thing... soak in vinegar for a few hours.
After all of that is cleaned out or changed out with clean replacement parts , have the pump pull some vinegar , say 2oz and then some clean water and then back to soda ash.

Right, but the problem is that water is flowing back into the tank. I didn't even know that was possible, but the whole flow is reversed. It doesn't seem to affect water pressure anywhere else in the house though, so I think it's somewhere around where the soda ash enters the water.