Mike, Have you tested your sensor using fresh city tap water?
Split from this topic. JasonLion
I would be very interested in the results you get with a new ORP sensor.
I have had two HI 98121 pH/ORP/Temp meters from Hanna for over a year (one has an intermittent value on the pH reading) and I really like them for the temp and pH values, but the ORP values have never really correlated with the Cl values I have in the pool.
I also recently purchased one of the epool monitors from Leslie's and that correctly shows cl ppm over or under 2.
I think it would be great to be able to use ORP as a chlorine indicator but the values I'm getting don't make sense.
I just ran a bunch of comparison tests and the results are below. Key takeaway from these tests is that for tap water I am getting the "perfect" > 600 mv whereas with the pool I'm getting much much lower values. Ive seen the 150 mV I measured today even go lower than 100.
I have seen the ORP values affected by static (plastic measuring cup on a dry plastic pool accessories storage box) so I wanted to rule out any container effect, and I checked the cl with different test kits and it's ok (pool is also very clear and clean looking).
Leslie's says I have high phosphates, could that be causing a problem?
I have some minor metal (copper probably) staining on the stairs, could that cause it?
Does the salt from the SWG have any effect?
Any other ideas?
SWG: 3300 ppm salt
fc 3 ppm
cc 0.5 ppm
ta 80 ppm
ca 30 ppm
Thermometer temp 32.2 °C
Fresh DPD kit
cl 3 ppm
pH 7.5 ppm
pool orp values (meter held directly in pool)
ORP 150 mV
pH 7.47 pH
temp 32.5 °C
Standing pool water in plastic measuring cup
Cold tap water in plastic measuring cup
Cold tap water in glass
cold tap water in metal saucepan
Fridge filtered cold water in plastic measuring cup (has only trace cl)
Gas heated tap water in plastic measuring cup