New Home With Inground Pool - Chemicals Out Of Whack! Help Please!

by Jennifer
(North Carolina)

We just bought a house with an inground pool that holds 17,300 gallons of water. It has a sand filter. The pool is 5 years old. We had it inspected and the following repairs were made: rebuilt multi port, replaced pump shaft seals, and replaced the pressure gauge.

I had a person come out to teach me how to backwash and rinse, and which chemicals to add when. We have a vacuum that we run often. My daughter got a rash, so I did a test strip with the "teacher".

Pool was low PH and alkalinity so we added the baking soda, shock, etc. I waited 2 days and took my sample to 2 pool cos. here. One said drain pool 1/3 and other sold chemicals to straighten out issues. We followed steps- added balance pak 100 (35 lbs), balance pack 200 (1.5 lbs), 4lbs smart shock, and 22 oz of algae inhibitor.

The water was crystal clear and since adding the above, the pool is now pretty cloudy.

The pressure on the gage runs between 15-17 normally. We backwash when it gets to 22ish.

Here are readings from tests at pool co (before adding the balance pak, etc. 1st number is 1st test, 2nd number is 2nd test at diff. store following day (after a rain):

Free chlorine- .7; 0

alkalinity(adjusted)-negative50; 0(store machine doesn't go below 0)

ph level 6.5; 6.2

calcium hardness- 22; 59

cyanuric acid- 150; not tested at 2nd store

saturation index- -4.92

No algae or mold showed up on tests and none is visible in pool. We do not know if sand has ever been cleaned (one company recommended Kleen it and/or replacing sand) or if it has ever been replaced.

I think the homeowner only added chlorine tabs as routine maintenance, and it has been suggested the pool water has been out of balance for some time to be this bad. How do we know what/where problem is?

Do we have to drain 1/3 of pool and if so, why? (We were wondering why 2 local pool stores had such a varying difference of opinion- one said "MUST" drain- the other said "NO- DON'T DRAIN!"

How do you determine if problem is in chemicals, or sand, or filter? What should we do?

Please help.... we have never had an inground pool and we want to resolve the issues before it gets out of hand.

Thank you so much!!

Thanks for the question Jennifer and thanks for the readings. It makes it much easier to clear up your pool.

I'm going to give you the correct readings for your pool so you'll see where it's off.

Chlorine 2 - 4ppm
Cyanuric acid (CYA/stabilizer) 30 - 50ppm
pH 7.6 - 7.8ppm
Alkalinity 80 - 10ppm. 120 should be the highest.
Calcium hardness 150 - 250ppm. This is mostly for plaster pools.
Metals 0
Total Dissolved Solids 0 - 1000ppm. 1500ppm and over and a partial drain and refill is needed

Is your pool plaster or vinyl? If plaster you'll need to get the hardness up in range, if it's a vinyl pool, don't worry about it too much.

I'd encourage you to get a Taylor FAS-DPD K-2006 pool test kit.
This is the kit that most pool stores use to test water.

Pool Water Testing

Water Testing Kit

I see the CYA is 150. It must come down and the only way to decrease it is to do a partial drain and refill. This needs to be done BEFORE anything else. The reason is if you get all the other chemicals perfect, you'll destroy them with the refill because you're diluting everything you just did.

The CYA is the stabilizer for the chlorine. You can have a high CYA, but the chlorine needs to increase in relation to the CYA. The chlorine is 7.5% of the CYA level and that's 30- 50ppm. As the CYA increases the chlorine must increase as well.

To get it within range of 30 - 50ppm, you're looking at a 3/4 drain and refill with new water. You need to test the fill water as well.

This way you'll know what's going in the pool. Say the pH of the water is 7.8. Your pH right now is 6.5ppm. By the time it's filled, your new pH could be 7.4, which is good and no need to adjust it.

I would encourage you to do a 3/4 drain and refill. Once filled, turn the pump back on and allow for one full turnover of the water. This is when all of the water has gone through the filter, about 8 hours. After that, take another sample of pool water to your local pool store and get me the readings.

Once I have the new numbers we can get your pool straightened out. Getting your pool right is easy with the numbers you provided, but again, once there, you'll need to drain/refill and start all over again because of the high CYA.

Watch the clarifiers and algaecides. You need to understand that an algaecide doesn't kill algae, it's used as a preventative measure. If you need an algaecide, I'd recommend a PolyQuat 60. This has no metals and is safe for vinyl liners.

Don't bother buying fancy sounding products, floccs, algaecides, clarifiers, etc...

You need:

Regular liquid chlorine. Don't use granular chlorine. It has a pH of 12. If you need to shock the pool the pH will go through the roof. You can use this for normal weekly maintenance, but not for a shock.

Dichlor chlorine (this is a stabilized chlorine with CYA already in it)


Baking soda (to raise the pH and alkalinity), or 20 Mule Team Borax to raise just the pH

Maybe some calcium chloride for the hardness

Trichlor tabs

PolyQuat 60 algaecide. This is to be used while you're getting the levels right and the chlorine level is low. Once everything is balanced you can stop using it.

Possibly some metal out, if your fill water has a high metal content. If there's no metals obviously you don't need it.

Here are pages and charts to see how much you need for your pool:

Swimming Pool Chlorine

Pool Shock

Pool Chlorine

Chlorine Tablets

Pool Chlorine Tablets

Swimming Pool pH Levels

Pool pH

Pool Alkalinity

Total Alkalinity

I've personally cleared up and balanced hundreds of pools with the few products I listed.


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