Chlorine won't stick around!!

[davidgelb]

Hi all,

I am so confused and frustrated, and I hope someone here can help me shed a little light on my problem. I am in Los Angeles and am getting my pool up and running for the summer. My pool is approximately 17,000 gallons and we recently had a FNS Plus 60 filter installed to replace a dead Pentair filter.

The pool is very old and in bad need of a replaster - we just purchased the house a couple years ago, but I am willing to be that this plaster is well over 25 years old. It is showing a lot of delamination and there is probably a little algae under some of the bubbled plaster, but nothing more than last year, and I had no real chemical balance problem.

Other than that, the pool is sparkling and everything seems to be in check, but my chlorine doesn't stick around for more than a day and a half to two days. Yesterday, I did a big chlorine shock using 2 gallons of liquid and one bag of Pro Side Super Shock Quick. Here is my information as of yesterday after the shock:

CYA = 87
Total Chlorine = 10
Free Cholorine = 10
pH: 8.2
Total Alk: 133
Adjusted total alk: 107
Total hardness: 300

After that test, I added 2.5 pts of muriatic to bring the pH down and retested this morning. Here is where I am as of today:

CYA = 90
Total Chlorine = 3
Free Cholorine = 3
pH: 8.2
Total Alk: 130
Adjusted total alk: 103
Total hardness: 292

My chlorine levels dropped 7pm in about 24 hours. And by tomorrow morning, I am willing to bet it will be at 0. I don't see any chlorine demand issues, and my conditioner is fine, so I have no idea what's going on. Also, I noticed that 2.5 pts of muriatic had no effect on the pH. So, I am not sure where to begin.

I did clean the filter completely - there was some algae, but nothing crazy, and it is completely cleaned out now, so I don't think I have algae depleting the chlorine.

Any help would be greatly appreciated, as I am out of ideas.

Thank you!!!

-David

 

[linen]

I did clean the filter completely - there was some algae, but nothing crazy, and it is completely cleaned out now, so I don't think I have algae depleting the chlorine.

How does your pool water look? If you suspect algae it would be best to start the shocking process. See: http://www.troublefreepool.com/pool-school/defeating_algae

Your cya level of 90 ppm is quite high and will require a minimum FC of 7 ppm to keep algae at bay (calculated by poolcalculator.com assuming a cya level of 90 ppm)and much more if you need to do the shocking process (see link above).

It looks like your test numbers are from a pool store? Many people have found that pool store results are notoriously inconsistent. It would be in your best interest to get your own appropriate test kit (see the link in my sig).

Also, I noticed that 2.5 pts of muriatic had no effect on the pH. So, I am not sure where to begin.

Most test kits read 8.2 even if the ph is well above that. For you pool add 37 ounces of 31.45% Muriatic acid (from poolcalculator assuming 17000 gallons, TA of 133ppm and borates of 0 ppm). Test again in 1/2 hour and redose accordingly until your ph is 7.5-7.8. If you are going to do the shocking process then lower your ph even a little lower to 7.2-7.4.

Let us know if you have questions.

 

[davidgelb]

Thank you! The pool water looks great, actually. Crystal clear and no sign of algae, and have previously shocked, so I don't know that I need to shock again, unless it would make sense to do so.

Would you recommend bringing the cya level down? If so, is there a way to do that without a drain and fill?

I will try testing again with my own kit and see if I get numbers that contradict the store's numbers.

Thanks again for the help!!

 

[linen]

Would you recommend bringing the cya level down? If so, is there a way to do that without a drain and fill?

There are folks that deal with high cya for awhile, but I would lower it since it is the beginning of the season. Unfortunately drain/refill and Reverse Osmosis are the only ways to reduce cya.

I will try testing again with my own kit and see if I get numbers that contradict the store's numbers.

What kit do you have? Post your results.

Could you put your pool/equipment details in your signature? It helps us.

 

[davidgelb]

Yes, I will put together a signature with all my equipment info today.

I do have the TF100, but some of my reagents are a year or more old - do they likely need replacing?

 

[davidgelb]

One other question...is this a safe guide to use for my levels?

Chlorine 2.0-4.0
pH 7.4-7.8
TA 80-120
Hardness 200-500
CYA 50-80

-David

 

[Smykowski]

Start with this chart.

 

[davidgelb]

Great! Thank you.

OK, so would you recommend I start by doing a drain and fill (gallons based on the Pool Calculator) and then get my levels back per the recommended level chart you posted above?

I have been chasing my chemicals around so much already, I would like to this so that it makes the most sense.

Thanks,
David

 

[Speedo]

Last year I had a CYA level of 95 and managed alright; I actually stocked up on 10% LC and ended up having a couple gallons left over (even after closing at 37ppm FC ). It didn't really seem that bad as far as LC costs.

I just found out that yesterday without the solar cover on, full sun from probably 10am-5pm that it can burn up about 3.5ppm FC. (without any use)

My CYA level is now 60 and it's definitely easier, but I'm still not sure if I would do a partial drain given the situation again. Maybe I was just lucky.


Don't get me wrong though, I was very vigilant in keeping it well above the target level and it was never even close to the minimum. At 95 CYA, I never let FC below 11. I believe on average I was adding 3-4ppm/day. As everyone will point out, if there is a problem it will be far worse at higher CYA levels.

Bottom line: High CYA levels will make things more difficult, but if you are willing to stay on top of your FC and never let it go below 11ppm, you should be just fine. This is also assuming you add enough FC at night to keep it above 11ppm by the end of the next day. It definitely requires learning your pool's needs.

 

[linen]

I do have the TF100, but some of my reagents are a year or more old - do they likely need replacing?

That is awesome...definitely the tool for the job I would guess your reagents (as long as they were stored properly) are fine. Although taylor recommends replacing the reagents every year, I have used mine for 2 years. There are some comments in the extended test kit instructions that discuss individual reagent issues: http://www.troublefreepool.com/extended-test-kit-directions-t25081.html

OK, so would you recommend I start by doing a drain and fill (gallons based on the Pool Calculator) and then get my levels back per the recommended level chart you posted above?

If you decide to do it, I would do the drain/refill first then deal with the chemistry. What type of pool do you have? Do you have a high water table?

 

[davidgelb]

Hmmm....yeah, I am not sure if I would be better off just biting the bullet and doing the partial drain and fill to get my CYA down to 30-50ppm, or just work with the higher level (at 90). Will it be easier to maintain everything with the lower cya level? If so, if might make more sense to do that, especially since the pool will have a solar cover on it during the week...I want to prevent an algae bloom as efficiently as possible.

On a side note, I am trying to more accurately determine the actual capacity of my pool, but am not sure how to given the shape.

Anyone have any suggestions on that?

Thanks!

 

[davidgelb]

Linen - I have no clue what the depth of our water table is...is there a way to find out? I don't even know where to begin.

My pool is a plaster in-ground.

 

[linen]

Linen - I have no clue what the depth of our water table is...is there a way to find out? I don't even know where to begin.

My pool is a plaster in-ground.

Where do you live? Do you have a dry well (a sump hole) by the pool? When you dig in your yard, how far down until your hole starts filling up with water (this time of year)? Sometimes you can call the county and find this information out generally for your area.

The issue is, if you drain below the water table, then a buoyant force is applied to your pool which at some point can make your pool a boat If you are not sure or able to find out, then it is best to do partial drains and refills. If you were to drain 25% of your water twice (drain refill drain refill), that should get you to about 50 ppm cya.

 

[davidgelb]

I am in Los Angeles (Culver City). No, there is no dry well by the pool and I called both the city and county and neither seem to have water table info.

I know our pool guy (he was awful and I eventually fired him) did a full drain and there were no apparant problems, but I am sure he didn't know what the water table depth was. Given this, should I just do two 25% drains? Should I leave any time in between to make sure that I am not re-draining new water, or does that not matter at all?

Thanks again for all the help!

 

[davidgelb]

One other question. I am doing my 1/2 drain and fill, and I noticed as it gets further down, the water in the deep end (over the main drain) has completely clouded up. Is this normal? What would cause this?

I have a thread going elsewhere in this forum about my main drain not working. Might this rule out a clog or a capped off main drain?

Thanks,
David

 

[linen]

I am not sure about the cloudiness. Are you draining through the drain? If yes, I would assume that it is working...or am I missing something?

 

[davidgelb]

No, I did the drain using a submersible pump. I have never gotten any suction through the main drain. Actually, I started a thread in another section here...if you are good with equipment, please take a look...I can use all the help I can get!!!

My post about the drain problem is here: http://www.troublefreepool.com/drain-not-working-t45818.html

Anyway, I just thought it was weird that the water got cloudy as I drained it, but I know I had some DE get into the pool after I last cleaned the filter, so maybe all the water moving down to the deep end just caused that DE to stir up and cloud the water.

Thanks!

-David

 

[davidgelb]

Do I need my pH in range in order to test the cya? I did approximately a 50% drain and refilled, but the cya is still testing very high...not much of a drop, but my pH is at 8.6, so not sure if it is possible to get a true cya reading. Should I try bringing pH down and retest the cya, or should I do another partial drain and fill?

 

[linen]

but my pH is at 8.6

How are you testing ph? Most tests (drop based) show no change above 8.2 (including the Taylor K-1000 that ships with the TF-100). If your FC is above 10 ppm, then your ph will read falsely high. If you are sure you are below 10 ppm FC, then I would definitely adjust ph down to about 7.2-7.4 right away.

Do I need my pH in range in order to test the cya?

I do not think high ph affects the cya test, but if yours is really 8.6 that is high. I would deal with ph first then measure cya after ph is down below 8. What does your water look like right now?

Is your fill water ph really high?

What was your cya test reading with the tf-100 pre drain/refill?

 

[davidgelb]

After doing about a 50+% drain and fill, my cya is still showing at around 80. pH is testing at 7.5 (which makes sense), chlorine at 0 and TA at 125. Should I just call it good on the conditioner and start chlorinating, or do I really need to do another drain to get the cya down to the 30-50 range?