Phosphates?

[Charlie]

Hi everyone,
According to the company that makes my chlorine generator (Pool Pilot), when Phosphates get over 1000ppm, the cell will no longer generate chlorine. I found this to be true last year as I thought something was defective with the cell. When I called Pool Pilot about it to return it for a new one, they asked me what my Phosphate level was. I bought a test kit and it was over 1000.

After reducing the level to 500, the Pool Pilot unit began working again producing chlorine, and I was able to get it to 100. What I don't understand is how the Phosphate level increases? This year, I noticed it climbing again to 500ppm. The only draw back with reducing the level is it increased my calcium level to 500 from 250. Is this bad?

I'm probably going to have to empty half my pool water to lower the Phosphate level since I don't want to increase my calcium level any higher.

[chem geek]

Charlie,

What is your pool's Cyanuric Acid (CYA) level and what was the Free Chlorine (FC) level before you found that the SWG wouldn't produce chlorine when the phosphate level went up? It is possible that the FC level was too low for the CYA level so the chlorine was getting used up fighting algae and the SWG couldn't keep up. Did you notice the water getting dull or cloudy when the SWG couldn't produce chlorine fast enough?

Did the manufacturer of the SWG give any sort of explanation for this? Did they say anything about phosphates directly interfering with their SWG?

I've been looking at getting to the bottom of what's going on with phosphates at this thread and so far it looks like one has to get to a rather high phosphate level above 3000 ppb before Ben's chart doesn't work as reliably. Most SWG pools are able to keep away algae and operate effectively with an FC level that is at least 4.5% of the CYA level up to around 3000 ppb in phosphates, but for a pool owner with 4000-6000 ppb in phosphates, they needed to keep the FC level closer to 7.5% of the CYA level which is the minimum level recommended for manually dosed pools. This is why I'm interested in your pool's FC and CYA levels and if you noticed the water getting dull or cloudy.

Richard

[CarlD]

Charlie,

What is your pool's Cyanuric Acid (CYA) level and what was the Free Chlorine (FC) level before you found that the SWG wouldn't produce chlorine when the phosphate level went up? It is possible that the FC level was too low for the CYA level so the chlorine was getting used up fighting algae and the SWG couldn't keep up. Did you notice the water getting dull or cloudy when the SWG couldn't produce chlorine fast enough?

Did the manufacturer of the SWG give any sort of explanation for this? Did they say anything about phosphates directly interfering with their SWG?

Richard

Bingo! Richard hits the bulls-eye again!

[Poolsean]

First, Phosphates will not stop the Pool Pilot from generating chlorine. It may create a high chlorine demand condition that can consume all the chlorine that is being generated. Actually, there's very little that will stop the Pool Pilot from generating. Very low salt levels, insufficient flow, and a depleted cell are pretty much the only things.

Second, phosphates can be introduced by vegitation landing in the pool, tile and vinyl cleaner as some contain phosphonic acid, and municiple water treatments use phosphates to prevent corrosion in their pipes.

Finally, phosphates have been around forever, but since we've been able to test for and treat it, it seems to gain more acceptance as the cause of problems. In the past we've always been able to overcome MOST situations of high chlorine demand by shocking to satisfy the chlorine demand. MY opinion is, and this part is only my opinion - not an AutoPilot stance, phosphates are not usually the cause and should be considered one of the last things to treat for.

Thank you for selecting Pool Pilot for your backyard investment.

[waterbear]

Sean,
Excellent advice again, as usual!

[CarlD]

The short answer is:

Phosphates didn't cause your problem. More conventional issues did.

Make sure your CYA, T/A, pH, CH and salt levels are correct.

[Charlie]

Thanks for the responses. The issue with the Pool Pilot was last year. As soon as I got around the 500ppm level, the unit began generating chlorine again. It was the first question that the Pool Pilot tech asked me while we were on the phone discussing the issue.

As of 11-10-07:
FC = 1.8
CC = 0
pH = 7.6
TA = 90
CH = 500
CYA = <20
Salt = 3000
water temp: ~60°F

The water is crystal clear. If you were to throw a quarter in the water, you can tell if it's heads or tails. Looks like my CYA is too low. I believe the correct range is 60-80? If I was to use triclor tablets, that will raise the CYA correct?

[aylad]

If I was to use triclor tablets, that will raise the CYA correct?

Yes, trichlor will raise your CYA. Just keep an eye on your pH--CYA will lower it. Of course, with a SWG, if you're having to constantly add acid, that would be a good thing!

Janet

[waterbear]

I would not use trichlor to raise your CYA since it is so low right now. It will take quite a while to get enough CYA in the water by using trichlor and CYA is important to make sure the cell is operating properly and not being overstressed. I sould just go ahead and add enought to bring your level up to about 70 ppm. Perhaps this was your initial problem since the phosphates really have no bearing on chlorine production but having low CYA and a chlorine demand or having the pool exposed to sunlight WILL make it impossible to maintain a FC level in the pool. Also, inspect your cell regularly for scaling since your CH is 500 ppm. and be sure to keep close tabs on your pH and do not let it get above about 7.8 since high pH is the MOST important factor in creating scaling conditions with high calcium. Scaling will also inhibit chlorine produciton.
Finally, once you get your CYA up into the proper range maintain your FC between 3-5 ppm. You should have no problem then.

[chem geek]

To add to what waterbear said, you have a couple of easy options to add CYA quickly. One is to use Dichlor since that dissolves quickly and for every 1 ppm FC added by Dichlor, it also adds 0.9 ppm to CYA. So using Dichlor as a chlorine source will help, but it will still take a while to add 60+ ppm CYA, but is something you can do in addition to the other option below (if you want).

The fastest and least expensive option is to get pure Cyanuric Acid (CYA). This dissolves slowly, however, so you need to put it into panty hose or a sock and hang it over a return flow. That way, it will dissolve in about a day, maybe two, if you keep the pump running 24/7 until fully dissolved. I suppose you could put it into a panty hose or a sock and put that into the skimmer (being careful not to fully block the water flow) as another option. Lastly, you could add it carefully and slowly to the skimmer (with the basket removed) directly and have it get caught in the filter, but that takes longer to dissolve (about a week) as the water flow per unit area in a filter is far lower than in the skimmer itself or from a return flow.

Richard