Electronic Chlorine, pH, and TDS sensors?

dschlic1

Silver Supporter
LifeTime Supporter
Oct 5, 2007
663
Valrico, FL
pH is easy to read accurately. Most TDS meters just read the conductivity of the water, so again are simple and cheap. The difficult measurement is chlorine. Some meters (none of the above) use a measurement called ORP and morph that into chlorine. If CYA is zero or close to zero, then ORP is a good measurement of the disinfection level in water. However at CYA levels 30 ppm and above it is useless. True chlorine probes are very expensive, starting at $500 and up. There was available a chlorine probe, perhaps 7 or 8 years ago that was affordable, but before I was ready to purchase, it went off the market.
 

Bosley

Gold Supporter
Silver Supporter
Nov 23, 2018
224
Edmonton, alberta
I Have the PH tester. Different Chinese brand but same unit. Check the calibration every few months. Works excellent. Use it in the hot tub every few days. I do compare it with my blue devil drop test every now and then and is perfect every time.
 

TexasBR

Well-known member
Aug 17, 2020
63
Houston, TX
pH is easy to read accurately. Most TDS meters just read the conductivity of the water, so again are simple and cheap. The difficult measurement is chlorine. Some meters (none of the above) use a measurement called ORP and morph that into chlorine. If CYA is zero or close to zero, then ORP is a good measurement of the disinfection level in water. However at CYA levels 30 ppm and above it is useless. True chlorine probes are very expensive, starting at $500 and up. There was available a chlorine probe, perhaps 7 or 8 years ago that was affordable, but before I was ready to purchase, it went off the market.
Thank you for putting this in perspective with the ORP, in the context of CYA. That is very helpful.
 

TexasBR

Well-known member
Aug 17, 2020
63
Houston, TX
I Have the PH tester. Different Chinese brand but same unit. Check the calibration every few months. Works excellent. Use it in the hot tub every few days. I do compare it with my blue devil drop test every now and then and is perfect every time.
It appears that electronic pH measurement is practical but Chlorine measurement is not (due to the unknown CYA issue).
 
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skybloke

New member
Apr 25, 2019
4
N. Bucks, UK
Ditto all the above. I have used the cheap Chinese pH/TDS digital types (your second pic) with great success. Re-calibrated yearly and checked a few times against a reagent test successfully. So I'd recommend those. Forget the needle type (first picture) as FC will be wrong as mentioned above, there's no way of measuring CC and the max range of 3 is next to useless!