Auto Pilot Total Control, PH always needs to be increased.

[dmw0150]

Hi There, I have an Auto Pilot Total Control System that generates Chlorine and also has a pump that injects acid (from a small tank) into the pool. The system has sensors to test ORP and PH and then automatically makes adjustments on its own to balance the levels. For about 4 years everything was great, then I decided to refinish the pool with an Epoxy surface instead of resurfacing it with another layer of Marcite. After I did that, the Auto Pilot system has never needed to add acid to the pool (i.e. the PH has always been low). Now I always need to add Sodium Carbonate to increase the PH manually. I spoke with Robert at AquaCal (the company that makes the Auto Pilot) and he said he does not know why the PH "slowly falls" instead of "drifting up". I know it has something to do with the Epoxy Finish, but I am not a chemist. By the way, I asked him if the company could re-program (or "reverse") the system "logic" so that I could put "Sodium Carbonate" in the tank and then when the PH gets low, the system could then turn on the pump to rise the PH. Brilliant idea, but he said that the system is hardwired and cannot be "re-programed". So bottom line, Does anyone know what I can do to get the water in my epoxy pool to always need acid instead of needing Sodium Carbonate (i.e. for PH to drift up instead of down)? Any help would be much appreciated.

[PoolDoc]

Hi Dale;

I've covered, at various times, why I don't generally like using ORP/pH controllers on pools, and I won't rehash that.

Regarding your situation, what I would recommend is disconnecting the AutoPilot system . . . and the pumps. That means PHYSICALLY disconnecting the feed lines. Feed pumps are often installed in such a way that they can feed 'automagically' and secretly . . . all by their little selves! Until you disconnect those lines, I'm not going to be sure that that's not happening right now.

By the way, you'll need to cap the injection ports. One way to do that is to take a little extra tubing, connect it, fold it a couple of times to crimp it, and use electrical tape to hold the folds together.

Then, run your SWCG and keep up with ANY other chemicals you are adding. Let's see what happens under those circumstances.

Regarding epoxy: it doesn't make the pH go down.

Regarding using soda ash feed . . . I don't recommend it, but you can do it if you really want to do so. Assuming that the AutoPilot system powers the feed pump directly, you can put a NC (Normally Closed) switch between your acid pump and your controller, and then set the controller to 'maintain' 7.4. That way, at 7.4 or below, the feed pump switch will be de-energized -- and thus, the pump will be turned on --but when the pH is above 7.4, the switch will be energized and thus the pump will be turned off. Of course, you have to mess around with the wiring and make sure you get all your voltages right, and purchase the correct switch. But, it's not that hard to do.

FWIW, the full blown commercial ORP/pH controllers all come with a switchable pH control circuit, to feed either acid or base.

[dmw0150]

Hi Ben,

Thank you for the reply and all the helpful information. I forgot to mention earlier that the acid pump has been disconnected for about a year now so I know for certain that the pump is not "secretly" adding acid to the pool. The pool manufacturer is puzzled because he says that normally pH will always drift up and not down. He said it had something to do with the "leaching" of the marcite. As far as "tricking" the system by putting a "Normally Closed" switch on the system, I don't understand how that would work because when the pH sensor senses that the pool needs acid, the acid pump does not continuously stay on, rather, it cycles on and off a few minutes at a time over a period of about an hour or so. Regarding the "switchable pH control circuit", I think that is an excellent idea and I have already contacted the manufacturer to see what they say about that. Thanks Again!

[waterbear]

Hi Ben,

The pool manufacturer is puzzled because he says that normally pH will always drift up and not down. He said it had something to do with the "leaching" of the marcite.

Nope! The manufacturer is feeding you a line because he does not have an answer for you! pH rise in a salt pool, whether it is plaster, paint, vinyl, tile, or fiberglass is PRIMAIRLY from outgassing of CO2. Primary water balance parameter that affects outgassing of CO2 is TA followed by pH and (with a salt pool, CYA since it has an effect on cell run time and therefore aeration of the water, which speeds up outgassing). My question is what is your TA? If your TA is low and your pH is low then raisin the TA could help (assuming that NO acid is being introduced into the pool, as Ben suggested above and that the plaster finish is fully cured and not introducing alkaline material from curing plaster).

FWIW, I have a fiberglass pool with a SWCG and it has a tendency for pH to rise and I have seen just as many fiberglass and vinyl pools with rising pH problems when SWCGs are used. Curing plaster can add to the problem but they are NOT the acutual primary cause of pH rise!

Are you manually testing pH or relying on the sensor? pH sensors do wear out and need to be replaced peridociacally and if they are allowed to dry out can be permanently ruined (such as when the pool was being refinished perhaps?). 4 years certainly is long for the life of a pH electrode!

Post a full set of test results done with a good test kit like a Taylor K-2005/6, TF-100, or PS-232,233,234 and we can take it from there.

[PoolDoc]

DWM;

If you were my local customer, and I was visiting, I would say "Hm-m-mh, let me take a look." and then proceed to verify everything you've told me. I can't do that.

So let me suggest that YOU do what I'd do next, if I were there.

I'd disconnect 100% of your SWCG and feed system (and make 100% sure you couldn't turn it back on behind my back -- been there, got blamed for the "inexplicable" problems, NO thanks), and then have you run with bleach for 2 weeks, and see what happens.

ALSO . . . I'd test your water, and especially your TA / CA with my OWN Taylor based kit. And THEN, I'd test your fill water.

But, since I'm not there, I can't do that. But it's what I recommend to you. You'll need a Taylor K2006 -- Amazon links in my signature.