decrease the pH salinity
 

Hello! I was just wondering if there are any inexpensive solutions or household products that I can
add to my water to decrease the salinity from about 8.5 to 6.0-6.5. Thanks!

You can use sulfuric acid (battery acid);
nitric acid;
hydrochloric acid (muriatic acid) used to treat swimming pools;
but these are very toxic and should be used with caution.
The safest to use is acetic acid better known as vinegar but not for long periods because it can be toxic to plants over time.
Ron