Reef Angel Forum

After about a month of working correctly, yesterday the pH reading dropped to ~2 and then raised to ~5. I recalibrated the probe. The reading for pH7 and pH10 went down respectively from 554 to 457 and from 832 to 741. When I put the probe back to the tank or sump it still reads ~5. When I test this probe in a cup with the water from the tank it shows 8.11 which is about right. So i thought voltage leaking in the tank. I tried to unplug every item one by one with no results, the reading remained in the ~5 range. Tested it in cup again and it shows over 8 which is correct. What could be the reason of the false reading when the prob is in the tank/sump? Also keep in mind that it just happened yesterday.

Can you check you float switches?

That was it, when ATO switch is unplugged pH reading goes back to normal.

Is there a way to fix this bad switch or I need to order a new one?

Was it the exposed leads that was touching the water or the float itself that causes the issue?

The leads are outside the sump and I isolated them with electrical tape, it must be the floating part of the switch.