1

I have total dissolved solids (TDS) meter which is built in to a water purification system and this meter always reads high, around 90-100 when the machine is turned on, but over the next 30 seconds or so while water is produced it gradually settles down to zero.

Is this likely to be some artifact of the meter or is the purification system somehow getting more contaminated when it sits out of use?

I suppose I could test this by generating two samples: a quantity of water produced by the machine at the outset, then a second quantity produced a minute later, then testing both samples with a separate, hand-held TDS meter. However, to do this test I would have to get another TDS meter.

Shaka Boom
  • 2,324
  • 15
  • 30
  • Sounds like there's a slug volume of water that gets moved through when you start the pump. – Todd Minehardt Jan 27 '22 at 03:07
  • Your hypothesis sounds plausible. TDS meters usually measure conductivity which can change in standing water if metal ions leach from the plumbing. What you are observing could also be a form of hysteresis. Hand held meters are not terribly expensive, unless you want a high quality device. Finally, it would help if you provided more information: type of filter, water, application (lab?), even temperature etc – Buck Thorn Jan 27 '22 at 17:51

0 Answers0