Best chlorine tabs to use?

[AE2000]

Hi, I'm trying to figure out the best way to keep the chlorine level in my pool decent, my pool is in direct sunlight all the time pretty much, if this makes a difference. But overall I'm wondering is bleach alone a way to keep chlorine maintained or won't that constantly need to be added to or is there a good chlorine tablet I can use so I don't have to add bleach all the time. Thanks.

(note: I did read chlorine section but still wondering if I have to go through alot of bleach won't my salt get to high in time and how would you lower it? so just wondering best method and I also don't have a pool cover at this time if that helps with keeping chlorine in?.)

[chem geek]

Without an automated dosing system (peristaltic pump or The Liquidator or a saltwater chlorine generator, SWG) and without a pool cover you would need to add chlorinating liquid or bleach every day or two unless you have the CYA fairly high and have big swings in chlorine levels. This is why Trichlor pucks/tabs in a floating feeder or inline chlorinator are much more convenient since they last around 5 days or so (longer if you use more in the unit and turn down the output).

Unfortunately, the side effect of using Trichlor is that Cyanuric Acid (CYA) usually builds up and makes the chlorine less effective eventually leading to algae growth unless you use a supplemental algaecide or phosphate remover. For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases CYA by 6 ppm.

So you can certainly use Trichlor pucks/tabs, but need to use PolyQuat 60 algaecide weekly or use a phosphate remover (a copper-based algaecide would work, but can stain the pool so I don't recommend it). All of these extra chemicals cost money, including the pH Up you need to use to maintain pH since Trichlor is very acidic. It's a cost/convenience tradeoff.

[AE2000]

ok thanks chem geek, I think I'll stick with bleach then but as for it adding salt how can I control that if at all ? I mean I'm still learning but I read in one of your post that the bleach/liquid chlorine puts salt in your pool how can you fix if it gets to high or does it matter? Thanks.

[chem geek]

ALL sources of chlorine result in increased in salt since for every 10 ppm Free Chlorine (FC) that you add, this will get converted to 8 ppm salt (as chlorine converts to chloride). However, most hypochlorite sources of chlorine add additional salt when added to the pool at this same rate of 8 ppm salt for every 10 ppm FC. So with bleach, chlorinating liquid and lithium hypochlorite you end up with 16 ppm salt for every 10 ppm FC.

Salt is fairly innocuous unless the level gets very high so it's usually not a problem. However, if you have very little dilution because you have no rain overflow, have a cartridge filter so no backwashing, minimal splash-out, then the salt will build up more quickly. Nevertheless, it will take years before it gets high. At 2 ppm FC per day chlorine usage, this is an increase of roughly 100 ppm salt per month or 1200 ppm per year if the pool was used year-round with that daily chlorine amount.

It's generally a good idea to replace some of your water anyway on an ongoing basis. Ideally, you can use rain overflow to do this (or there is no overflow explicitly lower the pool water level after a rain using a pump) or you can do partial drain/refill every now and then. There can be a slow buildup of hard-to-oxidize organics in the pool that can eventually lead to higher chlorine demand and sometimes dull water, but in the low bather loads of a residential pool this takes years with no dilution.

Richard

[Waterbucks]

I continue to find extraordinary information here and mostly from Chem Geek To follow up on this thread, I'm using an inline chlorinator with Trichlor pucks and (right now) a low level of CYA, around 30 ppm. We maintain a level of 3 ppm FC. However, to AE2000's point and CG's confirmation, I'm going to continue to gain CYA over time using the Trichlor. So, two questions:

1) at a typical rate of Trichlor usage, and with low levels of dilution, and without citing complex algebraic formulas , how long would it take to get to high levels of CYA?

2) when we open and close the pool, we use PHOSfree to remove/dimish the phosphates, is this enough to keep algea at bay as the CYA rises?

Thanks in advance for what I'm sure will be excellent advice.

Buck

[chem geek]

At a rather low chlorine usage of 1 ppm FC per day, continued use of Trichlor as the sole source of chlorine would raise the CYA by over 100 ppm in 6 months if there were no dilution.

A phosphate remover, like an algaecide, should prevent algae growth in spite of higher CYA levels and low FC levels, if phosphates were kept very low (< 125 ppb).

[Waterbucks]

Perfect! Thank you much for the information.

Buck

[chem geek]

Just note that you probably need to use a maintenance dose of the phosphate remover since some fill water has phosphates in it (mine has 300-500 ppb) and blown-in fertilized soil will increase phosphates. Also, the higher CYA level will slow down chlorine oxidation so you may find the water getting cloudy from higher bather load. You could then shock the pool with unstabilized chlorine to clear it.

Of course, if you were to manage the CYA level by using less stabilized chlorine and more unstabilized chlorine, you could just control algae growth and keep the pool clear using chlorine alone and not need to shock the pool regularly. It's less convenient since you have to add chlorine every day or two unless you have a pool cover, but it's also less expensive.

[Waterbucks]

I left out that detail, but we do add maintenance doses of the same phosphate product on a regular basis, albeit much smaller doses than the opening/closing additions.

Great idea on using unstabilized chlorine except that we use Chlor Brite to shock with which also raises CYA. I'm hesitant to use cal hypo as it's much more aggressive on the liner and raises CH which we have in range at this time. Apparently, some exercise of dilution is going to be necessary in a year or so regardless of whichever method of chlorination we go with. Either CYA is going to get us or CH will. Is that a fair statement?

Buck

[chem geek]

Yes, that's a fair statement which is why I suggested unstabilized chlorine, specifically chlorinating liquid or 6% unscented bleach. Just make sure you add any concentrated chemical slowly over a return flow at the deep end with the pump running to ensure thorough dilution. I would stay away from the Dichlor. It increases CYA faster than Trichlor and proportionately increases CYA more than CH (since CH is usually much higher than CYA). The following are chemical rules of fact independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it increases Cyanuric Acid (CYA), by 6 ppm.
For every 10 ppm FC added by Dichlor, it increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it increases Calcium Hardness (CH) by 7 ppm.

Even at a low 1 ppm FC per day chlorine usage, Trichlor would increase CYA by over 100 ppm in 6 months if there were no dilution of water.

[land21]

From reading there is no way to reduce the CYA unless you drain the water--however, using the Cal-Hypo which would be "shock" would increase the calcium hardness-but it can be reduced without draining the pool--correct?

Liquid the best--but need to add more frequently...the next best would be Cal-Hypo?

Am I understanding this correctly?

Thanks

[chem geek]

You can't reduce calcium hardness (CH) without water dilution -- at least not easily (one can partially sequester it to prevent scaling and one can precipitate it using oxalic acid, but that's messy). Chlorinating liquid and bleach do not increase CYA nor CH.

On a percentage basis, the rise in CH from Cal-Hypo is slower than the rise in CYA from Trichlor or Dichlor so in that sense it is "better" unless your CH is already high. As for frequency of addition, you have to add Cal-Hypo just as frequently as any other chlorine unless you have a special chlorinator designed for Cal-Hypo tabs (such a chlorinator being very different than the one used for Trichlor).

[Ralph Figueroa]

A certain Pool Supply company, starting with an L, makes the claim that their "chlorine tabs are the STRONGEST in the market." Help us all cut through the marketing crap and make a good decision! They say they have 90% available chlorine. Most of the containers of chlorine I have bought on the market say 93.5-94% Tri-Chlor. Give us the breakdown...Please!

[chem geek]

Actually, typical Trichlor tabs/pucks are 99% Trichlor which is roughly 89-90% Available Chlorine so I don't know which ones you are using (see . However, that's pretty pointless unless you are concerned with how much weight you are carrying when buying chlorine. 12.5% chlorinating liquid or 6% bleach can be less expensive per FC than Trichlor when accounting for the pH adjusting chemicals needed for Trichlor. Of course, with bleach or chlorinating liquid, you have a lot more weight to carry, but they do not increase Cyanuric Acid (CYA) levels. See Cost Comparison of Chlorine Sources though that post is older so prices are not current (but the way the calculations are done is still valid).

Look at poolgeek.com and see that Trichlor products from GLB are 99%. The 93.9% are BioGuard Silk Sticks because they have additional ingredients.