pH/ORP & pump

[rlpardue]

All,

I've noticed an intriguing (and slightly disturbing) pattern on my Neptune charts. Whenever my closed loop pump turns on, the pH and ORP both drop for the period until the closed loop is turned off. My closed loop pump cycles on/off a couple of times per day.

Why would the pH and ORP both drop whenever an extra pump is turned on?

The pump is a Dolphin Ampmaster 4750, with its flow split between a 1" seaswirl and an OceanMotions 4-way valve, leading to lots of locline outputs. The timer is currently set to run between noon and 2:30pm, then again from 4pm to 7pm. I haven't changed the timer for about two weeks, so there is some good data in the charts.

You can see my AC3 history on this website. Keep in mind that the probes are old and therefore inaccurate. However, the trendlines should be meaningful - you can see the ups and downs.
http://www.reeftronics.net/La/lee-p/ac3-status
http://www.reeftronics.net/La/lee-p/ac3-history

Video of my tank:
https://goo.gl/photos/N2FFHvwHasriQPBe8

 

[slief]

It would either be caused by interference from the pump or Ocean Motions or your closed loop is stirring up enough detritus to impact the ORP and pH. That said, that would be plausible for the ORP but not so much for pH. As such, I tend to think you are having an interference issue with the pump or OM and the probes. Do you have the probe wires running parallel to the pump or OM power cord? Perhaps try routing the probe wires differently and see of that helps or even moving the probes to a different part of the sump. The last possibility is that the OM is leaking power into the water. You can take a cup of tank water and place the probes in the cup outside of the sump and see if the readings change back to normal when the pump is on. If they do, then either the pump or OM have a voltage leak and I'd lean towards the OM.

 

[rlpardue]

That is actually a pretty brilliant analysis. I will try varying the wiring!

 

[slief]

That is actually a pretty brilliant analysis. I will try varying the wiring!

I will keep an eye out for your update. I'm interested to know what the root cause is.

 

[Greg 45]

I have the same issues with my GHL unit. They claim it's a earth ground issue. The power supply that came with my unit only has two plugs going into the socket the third round ground is missing. They also stated that the temp probe is not affected by this because there isn't any electric contacts in the probe. I had this issue for year on end , I would unplug the power bar and orp would go negative. This also affected salinity probe . Hope this helps.

 

[rlpardue]

I've been fooling around with the tank tonight and I think I probably have the same issue as Greg. My temp probe is the only unaffected probe. I tried moving all the probes to the sump and the issue continues. Tomorrow I'll try unplugging the OM but turning on the CL pump; I'm curious as to which item is causing the odd readings. Perhaps I could move the CL and OM over to a manual timer...

 

[Greg 45]

The issue has nothing to do with the pump and or pumps. The fault is in the control unit and the probes the way the systems are set up. GHL had me chasing my tail , if you remove the complete unit from tank like they had me try there is no issue . There should be standards and lab tests for all this equipment. We pay enough for these units not to be faulty. I cannot trust my unit any longer . Now the wanted $60.00 for a new power supply sorry to say man over board had enough.