Confused About Pool Chemicals

by Tom

I have an 18 foot new above ground pool and have followed the advise of a very reputable pool supplier. I am having two problems .

1. Sand coming back into pool even after following their advise, it continues.

pH and chlorine where very high and the pool is very milky and followed there suggestions.

So, I shocked the pool with liquid chlorine, waited 24 hours, then added a chemical to help the chlorine. Then pH is too high. Added pH down, however, still the water is milky after 3 days of filtering. Water tests showed everything ok so they said to add a clarifier. Now it is still cloudy and very frustrating

Any help understanding this would be appreciated.

Thanks for the question Tom

Understanding this is simple, but I'm walking a fine line here. I get these questions alot. They start out with "The guy at the pool store said such and such. I did it and now it's worse".

Check out these posts from very frustrated pool owners:

Do You Really Need All These Chemicals For A Pool Or Are They Just Trying To Get Your Money?

High Phosphates Over 1000 & Cloudy Water

First, I'd like to have your complete chemical readings: Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper). It makes troubleshooting much easier and the process of clearing up your pool will go much faster. You can get this done at your local pool store. They should do it for free. I'd encourage you to get a Taylor FAS-DPD K-2006 pool test kit.

Pool Water Testing

Testing Kit

Without these numbers I'm just guessing at what the problem is. I need to know what their advice was concerning the sand going back into the pool. Here are some posts to look over about this very issue:

Replaced Lateral But Still Sand In Pool

How Do I Stop Sand Going Back Into The Pool..Pool Keeps Getting Dirty..

Swimming Pool Sand Filter..Pool Seems To Be Manufacturing Small Debris

The question says the pH and chlorine were very high after talking to them. What were the readings? Then you shocked, I assume per their instructions, and added a chemical to "help" the chlorine. What was that chemical? The pH was still too high. What was it at that time?

Then the question says the water test were "ok", so why did they tell you to add a clarifier?

Since 1999, when I started my pool route in Arizona, and being the YMCA pool operator since 2008, I have found that many (not all) of these guys who work in pool stores are there to sell chemicals. They've never actually cleared up a pool...ever. This is what I meant when I said it's easy to understand why you're having these problems.

Get me the readings and answer the few questions I left for you and we'll get your pool back in shape.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Chemical Questions" category.

Swimming Pool Questions and Answers

Check back to this post for updates or answers.

Hope this helps and have a great Summer.


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Jan 18, 2015
Pool Water Analysis
by: Tom

Pool Volume: 28, 834 L
Sanitizer: Liquid
Finish: Vinyl
Location: Outdoor
Optimizer: No

Water Data
Temp: 29 C - 84F
T.D.S : 1000
Stabilizer: 0

Acid: 2
T.A 160 (125- 150)
Adj T.A: 160
CH: 175
Optimizer: 0
Copper: 0
Iron: 0
Mang: 0
Quat: 0
Algae: None
Clarity: Clear

After these reading they told me add 10L of liquid chlorine.

Thanks for the readings Tom

Your TDS is fine, but you'll want to keep an eye on that. At 1500 you might consider a partial water change.

Next is the TA at 160ppm. A little high but nothing some acid won't cure. Your pool is about 7600 gallons, which is what I use. To lower your TA to 100ppm, you're going to use 2.5qts. of muriatic acid. That's about 1.89 L.

You can add acid to one spot with the pump off for the alkalinity, wait about 3 - 4 hours, then turn it back on. Do this in the evening, then retest the alkalinity and pH in the morning and make another adjustment if needed.

Always wait for 1 full turnover of the water before retesting. This is normally about 8 hours. Very gently sweep the bottom and sides to break up any hot spots of acid. Don't disturb the acid too much.

Pool Alkalinity

Total Alkalinity

Hardness and pH are fine so don't touch them. When the acid is added it may affect the pH a bit, but not to worry. It will come back up through water movement and splashing around.

The stabilizer (CYA) is zero, so we need to get some of that in the pool. If you don't have that you're going to go through chlorine like crazy. You need to shock the pool. Use Dichlor shock. This is a stabilized form of chlorine. For 7600 gallons, about 1 lb. will raise the chlorine level to 10ppm.

You'll want to use a bit more (maybe 1 1/3 lb.) to get it to 12 - 15ppm. Go a little over, it's better than not hitting the 10ppm mark. Shock at night, then retest the chlorine and CYA in the morning. You'll see how much chlorine has been used through the night. Keep filtering 24/7.

Be careful when using Dichlor as it can get out of hand quickly. For every 10ppm of chlorine added with Dichlor, you'll raise the CYA by 9ppm. For every 10ppm of chlorine added with Trichlor tabs you'll raise the CYA by 6ppm.

Swimming Pool Chlorine

Pool Shock

Pool Chlorine

Chlorine Tablets

Pool Chlorine Tablets

Your CYA might be at 20ppm (or so) at this point. Shock it again with Dichlor and retest the chlorine and CYA after 1 turnover. When it gets to 30 - 50ppm, stop using Dichlor and switch to regular liquid chlorine.

Don't use regular chlorine granules to shock because it has a pH of 12. If you shock with granules the pH will go through the roof and you'll start all over again. During this process you can use a PolyQuat 60 algaecide as an added backup against any algae blooms that might occur.

The trick in clearing up your pool is to get the TA in line and keeping the chlorine level above 12ppm for a period of time. That's why you shock in the evening, retest in the morning, then shock again.

Remember to keep the chlorine level above 12ppm. This is the key point. Test and retest morning and night. Take a water sample to your pool store for analysis after every turnover of the water, or as often as you can. And remember when the CYA get between 30 - 50ppm, stop with the Dichlor, then use liquid chlorine. If you start with liquid chlorine now the chlorine will never hold.

No clarifiers, floccs, phosphate removers, etc... You don't need them and you'll end up getting more frustrated because the pool will continue to be cloudy, not to mention the additional costs.

Remember to back wash once per day. You're going to go through alot of water so keep the water level up 1/3 - 1/2 from the bottom of the skimmer.

Hope this helps and have a great Summer.


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