chlorine tabs and liquid chlorine

[houstonpoolguy]

I take care of my own pool and try to get advice and information from different places. i use 3 inch tabs in a chlorinator. the local pool store recommends doing one bag of shock each week to help with the chorine levels adn then do a good shock once a month (hot weather in houston means we are always in the pool).

when i just got my pool resurfaced i was asking questions and this pool company uses the tabs and then does liquid chlorine once a week to help with the chlorine levels. While researching i keep seeing don't mix liquid and tabs. Trying to get more info. any ideas?

 

[zea3]

Hi, welcome to TFP! We advocate our own method that relies on pool owner testing and liquid chlorine to maintain your pool. A properly maintained pool will not need weekly "shocks". Tabs and other forms of dry chlorine will either add CYA or Calcium to the water. Too much of either makes it difficult to maintain your pool. Dichlor and trichlor come in granules and tabs and add CYA to the water. In Houston you want to keep your CYA level between 30-50, maybe towards the 50 end at the height of summer in a manually chlorinated pool. When CYA gets too high you will have a difficult time preventing algae growth, as the higher the CYA, the higher the chlorine needs to be to maintain the CYA/Chlorine ratio.
Calcium hypochlorite also comes in granules and tabs and adds calcium to the water. When calcium levels get too high you have a risk of developing calcium scale, which feels like sandpaper and has diry, patchy appearance in the pool.
Both CYA and Calcium can only be removed by draining and refilling the pool.

 

[Dtkokay]

I don’t see any reason why you cannot add liquid chlorine to your pool while using tablets at the same time, as long as you don’t overchlorinate. They’re both ways of adding chlorine.

I’ve actually been doing that with my new pool while I learn how to adjust the tablet feeder for the right amount of chlorine. A few days ago the chlorine level fell a little low, so I added liquid chlorine to instantly bring the water up to the level I wanted.

 

[zea3]

I don’t see any reason why you cannot add liquid chlorine to your pool while using tablets at the same time, as long as you don’t overchlorinate. They’re both ways of adding chlorine.

I’ve actually been doing that with my new pool while I learn how to adjust the tablet feeder for the right amount of chlorine. A few days ago the chlorine level fell a little low, so I added liquid chlorine to instantly bring the water up to the level I wanted.

The problem is not over chlorinating, its over stabilizing with CYA. Most tablets contain CYA. Those that don't contain calcium. If you are going to use any form of dry chlorine you need to keep an eye on your CYA levels so they don't get to high and they will get high very quickly.
IN a 10000 gallon pool one 8 ounce trichlor tab will add 3.3 ppm of CYA by the time it completely dissolves. If you add 3 tabs per week, that is approximately 10ppm (9.9 if you want to be exact). Provided you start with your pool at the usual minimum 30ppm of CYA, in 4 weeks of tab use your CYA level is approximately 70ppm. If you also do a weekly "shock" with dichlor granules, then in that same 4 week period your CYA will be approximately 94ppm, and your pool will probably be green.
This is why regular testing by the pool owner with a high quality FAS/DPD kit is so important. You want to know what you are putting in your pool and what the effects will be. You can use tabs if your CYA is not too high, but you have to stop when your reach the top of the recommended range.

 

[mariane]

Welcome to the forum!
zea3 has got you covered.
Liquid chlorine adds . . . liquid chlorine.
Solid chlorine ie. pucks, powders add . . . CYA and chlorine. The problem with CYA is it "conditions" your water so the sun won't burn it off before it kills algae. If the CYA is high . . . >50, you have to add high amounts of chlorine to kill algae.
Using pucks and powders build up the CYA in the water until it gets high and you are force to use massive amounts of chlorine to kill algae.
So it's not really good to use the solid pucks when you need to keep your pool sanitized. Use liquid chlorine.
If you keep the chlorine levels where they need to be using liquid chlorine, you won't need to shock every week and you won't need to use tabs.
Here are good reads re: keeping your pool sanitized:

Pool School

www.troublefreepool.com

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.

www.troublefreepool.com

 

[ellislo]

Another effect of adding Trichlor is your pH level will drop too. In essence, you wouldn’t want to alter other chemicals level while trying to achieve your targeted FC.

 

[houstonpoolguy]

thanks for all the replies! Im new to owning a pool and new to keeping up with it myself. We had a pool guy for the first year, and watched and learned and have been taking care of it for about a year and a half now. but always learning, and getting new information. Didn;t know liquid chlorine was an option until about 4 weeks ago. Going to give it a shot, seems like CYA is a little high after we jsut got pool resurfaced. Resurfacing company said to give it a few months to get all the chemicals to settle and even out. Said to just keep an eye on TA and when that is in line, everything will balance with tabs and they do a gal of chlorine once a week to help. Can someone vouch for that???

 

[zea3]

CYA is only adjusted by either adding it to or removing it from the water. It is not found in fill water and degrades so slowly that the only effective way to remove it is to drain and refill with fresh water. That's why we say keep an eye on CYA levels if you use stabilized chlorine.
TA and pH kind of go hand in hand, but there are ways to adjust one with minimal effect on the other. Usually we only adjust TA to stop wide fluctuations in pH. Most of the time pH only needs tweaking once the plaster is fully cured. While plaster is curing the calcium levels may rise and pH will rise. It is important to brush the pool daily and to closely monitor the pH and adjust pH as needed.

 

[Palpatine]

This is a great thread... I live in So Cal and had similar questions about the 3" pucks. I'm a brand new pool owner and I recently resurfaced my pool in the Fall last year also. Did the startup and tried to balance the chems the best I could. Problem is we had a very cold and rainy Winter (for So Cal), so much so that my pool got close to overflowing a couple of times.

Was interesting to watch my PH levels rise off the charts in the Winter. I was constantly adding Muriatic Acid to bring it down and I only used liquid chlorine to chlorinate. Worked fine while there was minimal sun... but now the sun is back and I can't keep chlorine in my water. Turns out that I now have 0 CYA in my water. I think I had it to about 30 before the winter started... but I guess with all the rain it's now gone.

Was doing some research here and figured I'd continue with the liquid Chlorine and also supplement with some 3" pucks to bring the CYA back up. I might add a little bit of CYA... but I guess if I use a couple of pucks a week that my CYA level should be fine in a few weeks. I guess that's a question... am I understanding correctly?

Also was interesting that because of the cold weather and rain that I didn't have to add water to my pool for several months. Now, during lock down, I've heated my pool to 90 degrees and it's amazing how much water, and chlorine I guess, evaporate per day. Like an inch. I've also been keeping my pump running on high 24/7 for the last couple of weeks... is that too much stress on the pump?

Just refilled my test kit and will try to dial all the chems in as best as I can... but the good new is... no algae so far. I have a buddy who is a pool man and he says at least half the pools he's servicing have algae, probably because they're heated.

 

[mariane]

Was doing some research here and figured I'd continue with the liquid Chlorine and also supplement with some 3" pucks to bring the CYA back up. I might add a little bit of CYA... but I guess if I use a couple of pucks a week that my CYA level should be fine in a few weeks. I guess that's a question... am I understanding correctly?

You could do this but the problem is two fold - 1. it will take too long to get your CYA levels up which causes problem 2. the chlorine will be quickly burned off by the sun while you're waiting for the CYA levels to increase from the pucks.

You're best bet is to buy CYA at the store and put in enough to get it to 30-50 because of the hot sun and then use pucks to supplement if you get a lot of rain and have to lower your water levels a bit. CYA does not evaporate or loose it's strength. If you get it too high you have to do a partial drain. If it's too low it will not protect your chlorine from the sun.

Save the pucks "for a rainy day"

 

[Palpatine]

Thanks @mariane.

 

[Palpatine]

So glad to have found this forum. My friend is a pool man and he's telling me that "it's time to start using tabs in the pools" because that's what the management is telling him to do. He had no idea that the tabs have CYA in them.

 

[NYY]

CYA is only adjusted by either adding it to or removing it from the water. It is not found in fill water and degrades so slowly that the only effective way to remove it is to drain and refill with fresh water.

I read or heard somewhere that CYA rises to the top in a pool after it has not been circulating for a period of time. After leaving my pump off for a day, I overfilled the pool to push the top foot of water out of the overflow drain, and it worked to lower my CYA to the bottom of the range, from 93, if I remember correctly.

 

[mknauss]

I read or heard somewhere that CYA rises to the top in a pool after it has not been circulating for a period of time.

That is incorrect. The CYA is a dissolved solid. It would not 'float' to the top.

How were you testing your CYA levels? A value of 93 is not possible using accepted methods.

 

[NYY]

That is incorrect. The CYA is a dissolved solid. It would not 'float' to the top.

How were you testing your CYA levels? A value of 93 is not possible using accepted methods.

It was several years ago now, so don't recall the exact number. I used the blue test kit myself and then also took a sample to the pool store.

 

[NYY]

I suppose it would be easy to test this by taking a sample in the first 6 inches while the pool is circulating and then doing a sample a day later.

 

[mariane]

I suppose it would be easy to test this by taking a sample in the first 6 inches while the pool is circulating and then doing a sample a day later.

Depends on how you're testing it. Pool store results are not consistent. If you have your own test kit, you would know for sure since your regents and test procedure would be exactly the same from one time to the next.

The other test you could try is take a sample to the pool store and have it tested. Take another sample to a different pool store (or have a different person take from the original batch and walk into the same store 5 min. later) and have it tested. Then compare their results. It would be eye opening to say the least, especially if a different tester is working the machine each time.

 

[Palpatine]

I took my tap water in to Leslis's by my house to see what the calcium reading would be on my fill water and the CYA level came back at 50, lol. When I told him that's impossible because it's my tap water, he said "oh, that's weird... must have been some residual left in the bottle."

 

[mariane]

" must have been some residual left in the bottle."

Not uncommon.
The pool store near uses employees high school or young college age kids to do the water testing.

 

[zea3]

Your test results are only as reliable as the one doing the testing. That's one of the reasons we recommend testing yourself, so you know consistent methods and chemicals were used.