How to chlorinate with liquid chlorine so I maintain a residual free chlorine level throughout the day?

ArizonaBob

New member
Aug 26, 2019
2
Mesa, Arizona
Hi I am new to the pool forum, and relatively new to pool ownership.
I have a 10,000 gallon play pool and elevated spa equipped with a Pentair in floor cleaning system, a variable speed Pentair pump and a Pentair DE filter.
At installation the pool builder installed a Quick Dek-Clor erosion deck chlorinator.

At pool start up I spent a considerable amount of time reading about pool chemistry. I purchased a Taylor K-2006 FAS-DPD complete test kit.
I have been testing my water daily for free chlorine, combined chlorine, and PH. Once a week I check my total alkalinity, cyanuric acid, and calcium hardness.
I started using TriChlor 3” pucks. Once my cyanuric acid level reached 35 I started using liquid chlorine.
Each morning I would adjust my chlorine level to 3.0 assuming 13 oz of liquid should produce a 1.0 ppm rise in my free chlorine level.

What I didn’t realize was that as the Arizona summer got really hot a once a day addition of liquid chlorine wasn’t enough.
Due to bathing load and increased temperature I often found my chlorine reading in the morning to be very low.
I was adding upwards of 56 oz of liquid chlorine each morning. I also discovered that due to splash loss my cyanuric acid level had dropped below my ability to measure using my Taylor test kit.
After one typical Arizona dust storm and rain I ended up with a significant algae growth on the pool bottom. I thought it was dust from the storm, but after brushing the pool two days in a row what I originally thought was dust returned and I determined it was algae, probably mustard, but not sure. After 2 pool shocks and a lot of brushing the pool looks great again.
I went back to using TriChlor pucks not knowing another way to provide a constant supply of chlorine to the pool.

My question is given the problem of excessive cyanuric acid build up with TriChlor, how can you use liquid chlorine and provide a constant residual level of free chlorine?
It would appear you would have to test and dose your pool every 3 to 4 hours which is not reasonable.
I have seen comments on the liquidator chlorine dispenser, but some of the reviews are less than stellar.
Due to the amount of travertine decking, travertine pool coping and a natural stone wall at the back of my pool and around my elevated spa I hesitate to go to a salt water system.
Any recommendations?
Do I just live with the cyanuric build up and drain and fill when the level hits 80 ppm?

Thanks
ArizonaBob
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,428
Laughlin, NV
Welcome to the forum!
I do not suggest you continue to use trichlor exclusively. In your area, using a CYA of 50 ppm or so would be best. Then add liquid chlorine each day to reach the upper target for that level, FC/CYA Chart. That would be 8 ppm FC.
You will lose about 5 ppm or a bit more of CYA each month during the summer. So use trichlor when your CYA tests at 40 ppm. Or use granular CYA.
I do suggest your reconsider the use of a SWCG. Your travertine, if a quality stone, will not be effected. Low pH has far more effect on natural stone than lightly salted water.
I would also suggest you do a Overnight Chlorine Loss Test tonight. Take your FC to 10 ppm. Remove all pucks. Test 30 minutes after adding your the chlorine (after sun down) and then again in the morning before sun rise.
I suggest you read ABC's of Pool Water Chemistry.
 
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IceShadow

Gold Supporter
Jun 8, 2019
1,072
Milwaukee, WI
If you keep your CYA around 50ppm, you should be able to experience only a 2-4 ppm loss of FC per day. Your target FC at 50ppm of CYA is 6-8ppm, and you don't want it to go below 4 - so you bring it up to 8ppm daily and it won't drop below 4ppm.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
3,814
Damascus, MD
Trying to dose the exact amount of chlorine that you use daily is an exercise in futility and a sure way to always be battling algae. Chlorine has a range depending on your CYA level (see chart below). Target the high end of that range. You are safe to swim up to @ 3x the target level. If you get a bit too far above the high end of your range, simply don't add chlorine that day to allow the chlorine to drift down.

 

Edc1911

Well-known member
Mar 25, 2018
51
South Texas
I use a Stenner pump for my chlorine injection. The stenner pump runs every four hours (each cycle runs for 18min during the day and 6min during the night) to add about 64 oz of chlorine a day. I like to add chlorine through out the day, and I also run my VS pump 24x7. At 1100 RPM the pumps draws 85 watts. The parts list can be found on this thread, post #4 Stenner pump for chlorine. Help with sizing and install ideas
 
Last edited:

ArizonaBob

New member
Aug 26, 2019
2
Mesa, Arizona
Thanks everyone for your input and assistance.
Mknauss - I did the overnight chlorine loss test and my chlorine level dropped 1 ppm. This seems OK from the instructions.
I have read the ABC's of Pool Water Chemistry. Along with other reading I've done it was information I already had obtained.
IceShadow - the lass of 2 to 4 ppm of FC per day helps. Do you add liquid chlorine in the morning based on the FC measured?
PoolGate - I get what you are saying about the amount to dose, it depends on bathing load, temperature, rain, etc. Yet one has to use some method to attempt to provide enough residual chlorine. I guess I never heard that you are safe to swim at 3x the target level. Most documentation that comes with chemicals say's don't swim above 3.0. Which doesn't exactly work with a CYA level of 45. Targeting the high range seems reasonable. So I guess you are saying add chlorine based on size of pool and concentration of liquid to provide the high end of the range based on CYA. Is it best to do this once a day say in the morning or evening?
Edc1911 - A Stenner pump sounds like a good option. I need to investigate this further. Total cost seems about $400 is that about right?
 

JoeSelf

Gold Supporter
Jun 18, 2014
601
Glassboro NJ
I test and add chlorine when I get home from work. I usually add a couple of PPM over the high mark for Target. That way no matter what happens during the day I am sure to have enough to never go below the minimum for my CYA. adding in the evening gives the chlorine all night to work without any loss from the SUN.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
3,814
Damascus, MD
Thanks everyone for your input and assistance.
PoolGate - I get what you are saying about the amount to dose, it depends on bathing load, temperature, rain, etc. Yet one has to use some method to attempt to provide enough residual chlorine. I guess I never heard that you are safe to swim at 3x the target level. Most documentation that comes with chemicals say's don't swim above 3.0. Which doesn't exactly work with a CYA level of 45. Targeting the high range seems reasonable. So I guess you are saying add chlorine based on size of pool and concentration of liquid to provide the high end of the range based on CYA. Is it best to do this once a day say in the morning or evening?
This site doesn't prescribe to the pool store chlorine levels. It trusts in the CYA to Chlorine chart which is based in science and not a desire to sell you something. I add chlorine 24 hours a day since I have a saltwater generator. For manual additions, I think most people add it once a day. Not sure when most people add it. Once your chlorine is at the proper level based on the CYA/Chlorine chart, you would only be adding what you consume in a day. That should be fairly constant.