Chlorine tabs/ Liquid Chlorine

[jland47]

Just registered to the site but I have been referring to this forum for 2-3 years when I have issues with my pool. We have 60,000 gunite pool just recently replastered (this is our second summer with it being renovated). During the renovation I had new skimmers installed and plumbing around the filter/pump redone. When this occured I had the company install two automatic chlorinators (tabs) becasue I couldn't keep the chlorine level high enough during the summer with all the swimmers we were having. We replace the old pump with a Intelliflo 2 vst pentair and had the sand changed this year after having some green water issues. I didnt have any major issues last year but this summer has been a pain.

All this brings me to the old issue of liquid chlorine vs tabs, I've read a lot and I know everyone says liquid but, would this be the case for a small commercial pool. Larger waterparks use liquid chlorine with automated systems, I just wonder why our contractor wouldn't have recommended this, and no he doesn't sell the chemicals or had a friend selling them to me. Thoughts / comments?

 

[tim5055]

Welcome to TFP!!

It's very simple, Stabilizer/CYA. For every 10ppm of chlorine that the tab adds, it also adds 6ppm CYA. Eventually the CYA builds up to such a level that the chlorine is no longer effective in doing it's job.

Have you tested your CYA level?

How much Pool School have you read? Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

 

[mknauss]

Welcome to the forum!

Most pool builders have very little knowledge about proper pool water chemistry or how to manage it.

Your size pool is large for normal residential pools. An algae outbreak would be very expensive to manage unless you can change your water with little cost.

A Stenner automated chlorine injection would be viable. You would need a source of bulk chlorine. Would not want to fill it by the gallon from the grocery store!

Sand only needs to be changed in a sand filter if you have used too many pool store potions. Sand is millions of years old. It does not wear out.

Good luck -- take care.

 

[jland47]

FC- 2.1
TC- 2.49
CC- .39
PH- 7.7
HARDNESS- 225PPM
CYA- 89 PPM
TA- 67 PPM

Added 16 lbs of TA UP after this reading. And the pool is commercial use.

 

[tim5055]

What are you using for testing?

 

[mknauss]

Also - if this is a commercial pool that is normally regulated by your local health department.

TFP is for private, residential pools. Please do not use TFP methods if you are regulated by your health department.

Take care.

 

[jland47]

Bringing a sample to a pool store where they do a computer analysis. I have my own drop test kit that I watch the chlorine and ph levels mostly.

 

[tim5055]

Bringing a sample to a pool store where they do a computer analysis. I have my own drop test kit that I watch the chlorine and ph levels mostly.

Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. But, what can you do?? We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit. Order a TF100 and at least include the XL option. That will give you what you need while you are clearing the pool, and probably enough reagents for a couple of years normal use.

While you wait for it to get delivered, you have a homework reading assignment. Start with ABCs of Water Chemistry and Turning Your Green Swamp Back into a Sparkling Oasis

 

[jland47]

So lets say I decided to go with the liquid chlorine automation, am I safe to get a stenner pump and just adjust the tube size for flow rate? Is the 3 gpd considered a lot or should I go up a size in pump?

 

[dsmith99]

For a pool of your size I would go with the fixed rate pump 100psi in the 10 or even 17 gal per day size, then simply control the stenner with a timer. It will last much longer if it runs for shorter intervals and saves a lot of wear on the motor, rollers and the pump tubes. The tubes are interchangeable so if you decide you want to change its as simple as changing the tube.

You will likely be using 2-3 gallons per day depending on strength of the chlorine purchased. The 10 gallon per day is about .89oz per minute according to the pump spec.

You would probably want to source the chlorine by the drum as you would be using close to a barrel per month, that's a lot of jugs to haul. Liquid injection works great but handling that much each month might get old. Might not be so bad if you could find a source to deliver by the drum right to you.

A better option might be converting to a salt system to generate chlorine. It will be more expensive up front and require some routine maintenance but most who have them would never go back.

You should get your own kit and test at home. Pool store testing has routinely proven to be inaccurate and their advice is usually even worse. Get one of the kits mentioned above and don't look back. Check out the Chlorine-CYA chart, your FC level is entirely dependent upon your CYA level. As CYA increases from using all those tablets you need to maintain an even higher FC level to compensate.

 

[jland47]

Ok, Im doing some research to figure out what it would cost me per month to switch from tabs and granular shock to straight liquid chlorine. I can get a 55 gal drum of 12.5% for $135, does this sound reasonable anyone? Should I consider any other chemical cost if I switch to liquid chlorine?

 

[mknauss]

Review this -- Cost Comparison of Chlorine Sources

Be aware that liquid chlorine degrades over time. Especially due to heat. The high concentrations, such as 12.5%, degrade quite quickly.

So, if you can store the drum in a cool place, and use it within a month or so, it is a very good deal per ppm of FC in your pool.

Take care.

 

[harleysilo]

I've always been interested to read threads by people who maintain a public/commercial pool. If you have the funds, I'd go with SWCG.

 

[jland47]

Wouldn't the SWCG require more maintenance that an automated liquid chlorine injection system?

 

[mknauss]

The main maintenance with a SWCG pool is to manage pH. In some cases, depending on your fill water, a SWCG can cause pH to drift up. So acid additions may be required. The nice part is that it is a constant stream of chlorine to your pool. If you dose with a Stenner, it will be bursts of chlorine.

I assume you will need an ORP or something like that to monitor FC as you must maintain zero CYA? Most commercial pools are not allowed to have CYA.

Hope that helps.