57
Maintenance and Storage
Figure 73
Cleaning the pH and
pH/ORP sensor with hydrochloric acid
1 M HCl
Chlorine
bleach
Acid Soak
For heavy contamination or slow response after advanced cleaning,
remove the sensor from the bulkhead and perform the following steps:
1.
Soak the sensor for 30 to 60 minutes in one molar (1 M) HCl
(
Figure 73
). HCl reagent can be purchased from most chemical or
laboratory distributors. To prevent injury, carefully follow the HCl
manufacturer’s instructions. If HCl is not available, soak in white
vinegar.
2.
After soaking, thoroughly rinse the sensor with tap water. Then
soak the sensor in clean tap water for 60 minutes, stirring
occasionally. Finally, rinse the sensor once again with tap water.
Attach the sensor to the bulkhead and test the response time. If response
time does not improve or biological contamination of the reference
junction is suspected, continue to the chlorine bleach soak.
pH/ORP Sensor Maintenance and Storage
(continued)
Figure 74
Cleaning the pH and
pH/ORP sensor with chlorine bleach
1 M HCl
Chlorine
bleach
Figure 75
pH and pH/ORP
short-term storage
Bleach Cleanse
If biological contamination of the reference junction is suspected or if
good response is not restored by the previous methods, remove the
sensor from the bulkhead and perform the following steps:
1.
Soak the sensor for 60 minutes in a 1:1 dilution of chlorine bleach
and tap water.
2.
After soaking, thoroughly rinse the sensor with tap water. Then
soak the sensor in clean tap water for 60 minutes. Finally, rinse the
sensor once again with tap water.
Attach the sensor to the bulkhead and test the response time. If response
time does not improve the sensor may be nearing the end of its useful
life.
Short-term Storage:
When in regular field use, the pH-pH/ORP sensors should remain on the
bulkhead with the calibration/storage cup installed. Place a small amount
of tap or surface water in the cup prior to storage or transport. The
probes should be kept in this water-saturated air chamber between uses;
not submerged (
Figure 75
). Make sure the storage cup makes a tight
connection to prevent evaporation.
