Ph probe working or not?

[dradam]

With a lot of help from this forum I recently upgraded to full automation.

I am using the Pentair intellichem. firmware 1.030 rev B

I find that the ph reading is always about .7 lower than my measured samples. I have calibrated the probe and used the "tweak" feature but it is still off compared to my test kit.

Does it sound like a bad probe? or are there other tweaks any one can suggest. Thanks.

 

[chem geek]

That's way off. Does it measure incorrectly for your tap water as well? Usually tap water is in the 7.5 to 8.2 range -- often around 7.8 to 8.0.

 

[JasonLion]

Have you added any chemicals through the skimmer? Doing that can throw off the probe results for a number of days.

It is also possible, though rare, for the probe to become fouled with organic oils and give readings that are off until it is cleaned.

 

[dradam]

have not tested it against tap water-- will try it.

no chemicals added to skimmer-- borates sprinkled in pool but not skimmer.

Thanks for responding.

 

[dradam]

cleaned probe with detergent, have not tried muriatic acid yet-- this will be my next step

 

[Patrick_B]

Make sure you dilute the acid by at least 50%. I don't know these pool probes but don't think they are much different than those we use. None that I know of can handle a stronger acid solution without the loss of integrity. If you have pH probe storage solution or pH 4.0 buffer, give it an overnight soak in that first. It can't hurt.

 

[dradam]

Thank you, I did dilute the acid about 5:1 which Pentair recommends. Ph probe was replaced and same problem so I think it is the cable or motherboard.

Appreciate your help.

 

[Patrick_B]

Sure thing, sorry I couldn't help more. Let us know what you find out.

 

[dradam]

Thanks for your help and advice.

Problem fixed.

Turned out it was it was the cable from the PH probe to the Intellichem motherboard. Cable replaced, PH is reading normally and rock stable.

If anyone is reading this can you recommend what solution to store the ph and orp probes in over the winter. Pentair intellichem manual is not clear on this.

Thanks.