Chlorine Level ZERO

[SwimmingInWisconsin]

25000 gal in ground gunite pool

I opened my pool two days ago (May 24, 2021). Water is clear all the way to the bottom. No organic material in pool. Equipment running fine.

I've been testing the water everyday. Here is a summary

• CYA 40
• TA 100
• CH 275
• pH 7.2
• Cl 0

I can't test the FC because the R-0870 powder when added to 10 ml pool water DOES NOT turn red so I can't use the R-0871 solution to turn it back to clear and get a FC and CC reading. Thus, no TC measure. (My R-0870 and other testing supplies are from last summer.)

I used the Daily Test Kit to measure Chlorine and pH. Cl measures 0.

The summary above has been done everyday and the results are similar. CYA (40-50), TA (90-110), CH (250-275) pH (8.2-7.2), and Cl has been consistently at 0.

Each day I use the Pool Math and add what has been indicated. Thus far, over three days I have added the indicated amount of liquid pool shock (12.5%), muriatic acid (to reduce the high pH on Monday), Calcium chloride (to increase the CH). I have my Pool Math targets set at FC (4), pH (7.5), TA (100), CH (300), CYA (40) and 25000 gallons.

It has been sunny, dry and warm in Wisconsin: 76 degrees F right now. Rain forecast Friday and Sat.

What is happening with the Chlorine and how should I proceed? Right now, Pool Math is indicating I need to add another 102 oz shock, 45 oz by weight baking (washing) soda and 74 oz by volume of Calcium Chloride.

I have an inline chlorinator running and the arrow is set to medium-low. It has 3 inch Tri Chlor (90%) tablets inside.

What do you suggest I do to increase the Cl?

Thank you.

 

[Sunnydaze]

How old is the liquid chlorine? It degrades over time and you may not be adding as much chlorine as you think. Or something in the pool is consuming it quickly.

 

[Oly]

30 minutes after adding liquid chlorine and running your pump, test your water for FC and see if you have reached your intended target.

 

[JohnT]

You will need to test and add chlorine several times a day until things get cleaned up. Once a day isn’t often enough.

 

[magiteck]

All of the advice given so far is good. Just wanted to add that just because you can’t see anything growing in your pool, doesn’t mean there’s no organic material there.

If the there was 0FC in the water when you opened, and especially if the pool water was warmer than 60 degrees, odds are good that there’s something there. Your inline chlorinator and the liquid you’ve added have likely kept it just low enough to avoid a visible outbreak.

If you want to rule out testing error, if you’re on city water you can test your tap water. It should have chlorine in it.

My hunch is that a quick SLAM Process will be in order.

 

[SwimmingInWisconsin]

How old is the liquid chlorine? It degrades over time and you may not be adding as much chlorine as you think. Or something in the pool is consuming it quickly.

Thank you for your help. The liquid chlorine is new this season.

 

[SwimmingInWisconsin]

30 minutes after adding liquid chlorine and running your pump, test your water for FC and see if you have reached your intended target.

Thank you for your help.

I added the recommended amount of liquid chlorine and tested after 30 minutes. Here are the results:
FC 2ppm
CC 1 ppm
TC 3 ppm

Not quite the recommended level (target is TC 4 ppm).

What do you suggest as a next step?

 

[SwimmingInWisconsin]

All of the advice given so far is good. Just wanted to add that just because you can’t see anything growing in your pool, doesn’t mean there’s no organic material there.

If the there was 0FC in the water when you opened, and especially if the pool water was warmer than 60 degrees, odds are good that there’s something there. Your inline chlorinator and the liquid you’ve added have likely kept it just low enough to avoid a visible outbreak.

If you want to rule out testing error, if you’re on city water you can test your tap water. It should have chlorine in it.

My hunch is that a quick SLAM Process will be in order.

Thank you. I tested my tap water (city water) and it did show a very low amount of FC - about .5 ppm, so it seems the testing kit is viable and there is/was no testing error.

Do I start a SLAM now, in your opinion?

 

[SwimmingInWisconsin]

You will need to test and add chlorine several times a day until things get cleaned up. Once a day isn’t often enough.

Thank you. So you are saying I should check the FC and add chlorine (using the Pool Math calculator) and do that several times per day? Someone else suggested using the SLAM method. I'm trying to figure out if I should just test, add, test, add etc OR SLAM (to the higher chlorine level.

 

[mknauss]

What do you suggest as a next step?

Follow the SLAM Process

 

[Oly]

Yes, stock up on liquid chlorine now and get a SLAM started. The more diligent you can be about keeping your FC at the SLAM level the faster this will end and you can start swimming.
All of your other numbers look good for now so don't test anything but FC now and add enough liquid to maintain your level. Use the 10ml sample to save reagent.
Be sure to read and reread the process from the link Marty provided and don't cut any corners.