Pool water chemistry help

[bigkevj]

OK, so after all of you telling me you cant help me until I test it with a TFP approved test kit, I figured out how to use my Taylor K-2006 test kit and did some testing on my new pool.

FC - 5.4ppm
CC - after 5 drops of 0003 it did not turn pink
PH - 7.2
TA - 80ppm
CH - 200 ppm
CYA - the water level was well below the 100 mark, so its pretty high.

I know to handle the CYA, all I can do is drain, so I will wait until we winterize the pool here in KS and deal with that at that time. FC is a little high, I have an automatic feeder feeding dichlor granules, so I turned it down a bit.

Other thoughts?

 

[JVTrain]

Not sure if it's been mentioned but I'd get off the dichlor granules ASAP. They're only driving your CYA higher. Switch to liquid bleach, manual dosing.

You have two things working against you, causing your water to be corrosive to your plaster at this point. Your CH is low and your CYA is high. Right now your CSI is likely in the -1.0 range, meaning it's corrosive to your plaster/tile/concrete. Here's how you can correct it. Bringing your CH up to 350 will and allowing your pH to rise to 7.8 will get you to a CSI that's at least greater than -0.6. The other way to approach it is to lower your CYA level. Because you don't know exactly what it is, it's hard to tell how much that will change your CSI. High CYA also makes the CSI more negative.

You should repeat the CYA test, diluting your pool water 1:1 with tap water. Then multiply the result by 2 to get your actual CYA.

Your FC is not high. Not at all for a CYA that's over 100. In fact, it's low for maintaining sanitation. See the [FC/CYA][/FC/CYA].

 

[Mr Bruce]

You could do the dilution test to see what your CYA is near, although it doesn't matter you are going to have to drain anyway.

That dichlor feeder is not doing you any favors, I'd empty it now and switch to liquid chlorine only.

 

[duraleigh]

A dichlor feeder?? Man, that is doing you no favors at all! That will be a source of continually high CYA until you empty it.

 

[JVTrain]

The only dichlor feeder I know of is the Jandy model... but perhaps it's actually the very common trichlor tablet feeder. Maybe a simple mistake.

It does make a difference, however, because:
Dichlor = 1 ppm FC + 1 ppm CYA
Trichlor = 2 ppm FC + 1 ppm CYA

Dichlor will raise your CYA over time much faster than trichlor.

 

[bigkevj]

What is CSI? that is a new acronym to me. And how do I bring up CH? I will try the diluted test.

My feeder is granules, not tablets. It looks very similar to this:

 

[JoyfulNoise]

I agree with the other posts, that dichlor feeder is doing you no good at all. You can only use stabilized chlorine (dichlor, trichlor and cal-hypo) if you are very methodical about replacing water. So basically, by using dichlor, you also need to be on a strict regimen of backwashing your filter and periodically doing partial drains. In effect, you need to manage your CYA and FC levels. This is why we don't suggest using those products, it costs A LOT more in the long run than using straight bleach.

Since you need to raise your calcium hardness and because your CSI is so negative, you could switch over to cal-hypo chlorinating powder for the rest of the season. This will stop your CYA from increasing and still allow you to use a solid chlorine source. However, you CAN NOT put cal-hypo in that feeder. Feeders are designed to work with only one type of chemical and if that feeder is using dichlor, then that's it.

The cal-hypo will also add CH and alkalinity to your water (from the excess calcium carbonate and calcium hydroxide in cal-hypo). So you will need to watch your pH while using it as it will want to rise. Even when properly used, cal-hypo can cause temporary clouding of the water that typically resolves with 24 hours of filtering.

One downside of high CYA in a closed winter pool is that there are certain types of bacteria that will use CYA as an energy source and they can produce ammonia. So, on some occasions, people will open a pool that had high CYA, find that the CYA is a lot lower than expected and then have an impossible time bringing the FC up because of all the ammonia in the water. I mention this because it is another strike against using a dichlor feeder and having high CYA.

 

[JVTrain]

CSI stands for calcium saturation index. It is a relative number that is derived from many of your chemical test levels. It is calculated using a long, complicated formula using your CYA, TA, CH, pH, salt, temperature and optional borate levels. It is calculated based on your inputs for you near the bottom of the colored area table on the Pool Math page (green row).

This number gives the total corrosive or scaling tendency of your pool water. Zero is completely neutral, no scaling, no corrosion. Negative values indicate a potential for pool wall corrosion. Positive values indicate potential for pool wall scaling. If your water has a CSI index between -0.6 and 0.6, you should not have to worry about corrosion or scaling. If your CSI is greater than 0.6, you have a good chance of scaling on your plaster. If your CSI is less than -0.6, you have a good chance at corrosion of your plaster.