ORP probe question

hart24601

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Hey Mr Randy, or other chemistry experts, I run ozone into my skimmer around 10mg/hr. Where is the best place for the probe - in sump or in the external overflow? If I leave it in sump it reads quite a bit higher, enough to shut the ozone off at 450. If placed in overflow it's about 330.

Another question, I read that when the probes get dirty they read higher, but I noticed my ORP was always around the 230 range even if I bubbled ozone next to it. I cleaned it with a soft brush and the reading went to the above numbers.

For anyone interested, I was running the ozone with just the suction from the skimmer, but just for fun I attached a small air pump behind the drier tube and it seems to be working much better. Maybe the skimmer wasn't able to pull enough air through the internal area of the generator? But I can run more ozone without smelling it, so I think the generator might have been leaking a little bit without enough airflow.
 
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hart24601

hart24601

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Follow up question, the ORP probe has a small hole in the top cap, is that just for when they filled it or does that need to be exposed to the air? It's a BRS lab grade probe.
 

DaveMorris

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When I was running ozone on my 300g tank I had the ORP probe in the overflow. I don't care what the O2 level was in the sump. I was more interested in what the overall level was in the display tank. As for cleaning, I would add that to a monthly maintenance list. In fact, I do that with all of my probes just to keep them as clean as possible. I think it depends a lot on the particular system as to how often the probes really need to be cleaned.
 

Randy Holmes-Farley

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That hole is likely a fill hole for the reference solution. It should be plugged to prevent seawater from entering or solution from evaporating or spilling out into the tank.

FWIW, not all ORP probes are refillable. None I have had are.

I'd personally keep the probe in the sump.
 
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hart24601

hart24601

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Thanks Randy! The hole might very well be sealed inside - I doubt it's really open all the way internally, but I will ask BRS to be sure but if it's open there would be seawater in there by now. Would it spill out? I have had it upside down with no issues.

What is your take on ozone and ORP in sump vs tank? Like I said the sump reads very high, but the skimmer is large and takes up a lot of room, so the probe can't be mounted too far from the discharge. I only run about 15mg/hr.
 

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