I have a water sump under my tanks for overflow water. I test this water for TDS periodically and replace it if the readings get too high. This past week the readings were over 400ppm. I changed the water with new RO water and the reading remained over 400ppm. Fearing that my RO membranes were shot, I went into the basement and checked the RO water and got a reading of 5ppm. Now - I'm confused so I check all of my water.
The water I just removed from the sump is 6ppm (in the bucket in another room). Another reservoir is 5ppm. I recheck the sump and it is reading over 400ppm (still).
I now remove a cup of water from the sump & go to another room and get a reading of 5ppm.
Evidently, the electric / electronic equipment in the vicinity of the sump is causing the meter to provide erroneous readings. I've never seen this before nor heard of anyone else having this experience.
I'm interested in hearing of other theories or experiences ...