Interesing Zodiac TRi issue with pH

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R

rthorntn

0
Jan 8, 2013
59
Sydney, Australia
Hello you very helpful bunch,

TRi is 4 years old, I just noticed the chlorinated side of the cell has a brown residue all over it, I took it out and cleaned it (for the first time), it could be one of the cables to the electrodes rusting, not sure.

So my guess is there is brown residue going down the cell outlet pipe and the sensor / acid feeder pod, the pH sensor had some brown gunk on the glass bulb that I wiped off.

The strange issue is that with the chlorinator off (0%) the pH reads correctly at a low 7.0 (FAS-DPD) but with the chlorinator on, so I can see the chlorination bubbles the pH jumps up to 8.0 and then the acid turns on, as a temporary measure I have disabled the acid pump to let the pH climb overnight.

Very strange.

Thoughts?

Thanks for looking.

Cheers
Richard
 
Nice to meet you via TFP :)

The water should flow per this sequence of equipment: Pump - Filter - pH pod - SWG cell. Is that how it's laid out?

Try to clean the pH sensor without rubbing it. Maybe just dip it and swish it around if that will do the job.

pH is tested with phenol red. FAS-DPD is the preferred test for free chlorine.
 
Thanks needsajet!

The pH pod was indeed installed in the wrong location 4 years ago (it's after the SWG cell), I will plan to have the plumbing redone (looks like the pod clamps on so maybe the move might be easier than I thought).

Apologies when I said FAS-DPD I was referring to the Taylor "FAS-DPD" blue box, the Rolls-Royce of test kits but yes I was using the correct solutions for pH :)

Right so clearly the pH pod should be installed just after the filter so it has the cleanest water to test but my incorrect placement worked well for 4 years, any idea what could be causing the pH rising when the cell is active, so I could "band-aid" it until I get the order redone?

Thanks again.

Richard
 
Welllll, I'm not a big fan of pH automation, so I'm a bad one to ask. I think it's tends to make people use more acid than they need to use, plus the sensor needs maintenance. For me, testing weekly and pouring 300 ml of acid is not a big deal. So I would just buy a plastic measuring cup and turn it off. Or could you turn up the pH setting?

Puzzling why it just started. I can see why it's happening (the SWG raises pH in the return water). I think the only thing that could cause it to start happening when it hadn't been happening before, would be a reduction of flow rate (dirty filter or skimmer, something stuck in a pipe somewhere, new lower speed pump, or something) Just guessing because I have no experience with it.

Yeh, the Taylor kit is noice. Glad to hear you have one :)
 
Thanks again needsajet!

The pH and acid feeder pod has been moved, still getting wonky readings (haha but now it's lower around 6.0pH) when the chlorinator is running, I'm starting to suspect this part of the manual holds a clue:

"pH & ACL sensor cables must not be close to high voltage cables to prevent false readings."

Now could the chlorinator power cable be classed as high voltage, I wonder if it's possible that the pH probe has become susceptible to interference from the chlorinator power cable over the years?

I have a replacement probe and cable and will probably install it, the current probe is 4 years old.

EDIT: Actually comparing the old and new pH probe cables, on the old one I can see some exposed metal at the probe end where it joins to the BNC that must be covered by the rubber sheath on the new probe cable.
 
Replaced the pH probe and cable, calibrated with new fluid.

Still having issues.

I investigated some more...

The pH climbs past the set point (7.5) then the pump motor starts up to deliver acid, so the pH reads 7.6, I see the pump move for a few seconds and all of a sudden the pH is 5.8 which is stopping the pump, it just goes round in a loop (7.4, 7.5, 7.6 [motor starts], 5.8, 5.9...) and acid is not delivered. So the peristaltic pump motor or circuitry connected with it is messing up the pH readings, anyone got any ideas?

Thanks.

Richard
 
I guess I would try keeping the wires separated, but I don't have much confidence it will help.

Here's the service manual, with the Tri pH trouble-shooting section around page 22. Zodiac Tri Ei and pH Large Manual.pdf - Google Диск

Just to catch up, is this correct? The sensor is now relocated and is after the filter and before the salt cell, on a horizontal pipe. The injection fitting is closer to the SWC cell than the sensor. Or in other words, the injection point is downstream from the sensor, e.g. if the flow is left-to-right, the injector is to the right of the sensor.

Hopefully there's an Aussie or European that has some experience with the Tri pH that will chime in. Or anyone else! Here's the Tri pH manual for reference: http://www.pumpshop.com.au/wp-content/uploads/zodiac-tri-ph-water-care-system-manual.pdf
 
Thanks needsajet!

Not confirmed, if the flow is left-to-right, my injection point is to the left of the sensor!!!

I can't see that stated in the manual but it seems obvious to me now.

I will change it round and lt you know what happens.

UPDATE: turned the sensor pod 180 degrees and it all appears to be working, pH is 7.1 because we manual dosed but I calibrated so that the acid pump came on and it kept running, also the pH seems stable!
 

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