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pH/chlorine regulator AUTODOS 5000 - 2005-01-21
Eng_Autodos5000.doc ver 3.2 - page 28
4.3. Measuring Free/Combined Chlorine
Free chlorine can be measured with special measuring cells. Combined chlorine is measured with a measuring cell
for total chlorine and when the free chlorine value is subtracted from the total, we get the combined chlorine value.
4.4. Free Chlorine Regulation by Free Chlorine Measurement
Free chlorine regulation use the direct measurement of free chlorine ions (in mg/l) to control chlorine dosing. A
suitable value in normal pool water is 0.60 mg/l and 1.00 mg/l in bubble pools (dependent upon the pH value).
When installation of an AUTODOS 5000 with free chlorine electrode in swimming pools, that have previously been
treated with organic chlorine (trichlor or dichlor), the pool water must be changed. This is because the cyanuric acid
content in the pool water, caused by the organic chlorine, results in an exceptionally high value of chlorine when
DPD no.1-testing, thus making a correct calibration impossible. The chlorine cells show the free chlorine value,
whereas a DPD no.1-test shows the free chlorine together with the cyanuric acid bound chlorine.
4.5. Combined Chlorine Regulation
When there is too much combined chlorine in the water, the total (co free) chlorine level can be reduced
with UV light or active carbon.