UV Sterilizer Increasing ORP Rapidly

[CheifReeferNB]

I recently installed a Pentair 40 watt UV sterilizer on my 170 gallon tank. I have the pump circulating at about 160gph. After installation, my ORP has shot up from the low 200s to 450 over the span of two weeks, with a large jump almost immediately. Is this normal for a UV sterilizer or should I be concerned?

I will add there is no ozone on this system currently so that is not a variable.

 

[Randy Holmes-Farley Verified Community Expert]

There is no concern of the ORP getting too high from a reasonably sized uv.

Where is the probe in relation to the uv outlet? If just downstream of it, it may be giving a false sense of the main tank ORP.

You might also unplug the uv for a minute and see if ORP drops instantly, which could suggest electrical interference.

The rise from 4/9 to 4/16 may also just be calibration drift of the electrode.