Not sure about Pool Closing Chemistry

[xsmarc]

In-Ground Gunnite Pool
POOL size: 40,000 gal
Filter: Hayward, DE-4800
No Heater

I am in central Jersey.

I will have my pool closing/winterization next week by a company. I am however taking care of the chemistry.

I am not understanding a few things:

1. What does it mean by bringing the pool to Shock Level FC?

2. Can I Shock the pool and throw in algaecide at about the same time? (There is no algae in the pool right now)

3. Last Sunday evening, the FC level was 0.5, I used 1lb shock (which according to the label treats about 16k gal., my pool is 40K gal.), ran the filter for 6 hrs, when I tested the water next day the FC was at 5.0, Is this normal? I want to use another 1lb of shock before the pool is closed next week. Should I do that?


Thank you
Mrac

 

[BoDarville]

xmarc:

Welcome to TFP!

To familiarize yourself with pool water chemistry, I would start here: ABC's of Pool Water Chemistry. This will give you the foundational knowledge needed to manage your pool.

This will help us determine how much chlorine you need to add in order to bring your pool to shock level. At a minimum, we will need free chlorine (FC), combined chloramines (CC), CYA (stabilizer) and pH levels. Shock level is not the same for every pool, despite some industry and pool store claims otherwise. The amount of chlorine needed to achieve shock level depends on the CYA level. This is explained in the ABC's article.

What kind of shock product did you add to your pool last Sunday evening? Need active ingredient (preferred) or brand name.

After reading the ABC's article and posting test results, we will have more information that will help us address the specifics associated with properly closing your pool for the season.

 

[pwrstrk]

Welcome to TFP !
I agree with the advice Bo has given ya. Good advice.
I have a question for you, what test kit are you using? If your not using one of these Test Kits, I highly suggest you purchase one. We base our advice on accurate water testing and one of these kits will give you results that you and the forum can trust. I use the TF100 kit. Best value and the best customer service !!
Hope you enjoy the forum and when you have questions don't hesitate to ask ?

 

[xsmarc]

BoDarville and pwrstrk thanks a lot for responding,

Here are the test results:
Before shock - PH 7.3, Alk 90, FC 0.5, TC 1, CC 0.5
After shock - PH 7.5, Alk 100, FC 5.0, TC 5.0, CC 0
Haven't bee doing CYA test as it is not available in my test kit (I think).



I bought chemicals at Leslie's Pool Supplies, a local chain. The product is called POWER POWDER PLUS and it contains 73% Calcium Hypochlorite as active ingredient. The label also says "Minimum 70% Available Chlorine".

The test kit also came from Leslie's- Its called "Taylor K-1004 Deluxe, made by Taylor Technologies.

Thanks again,
Marc

 

[BoDarville]

Thanks for posting those results. You are correct in that the K-1004 does not contain the CYA test. However, this test is a must-have. Optimal chlorine levels, both normal maintenance and shock levels, depend on the CYA level (Chlorine CYA Chart). That's why the conventional "wisdom" of maintaining a chlorine (FC) level of 1-3 ppm is totally false. The chlorine/CYA relationship is the cornerstone principle of the TFP method. Understanding this relationship will eliminate 80-90% of the issues most pool owners experience. Not knowing the CYA level is why I could not recommend the proper shock level or chlorine dosing amount.

In addition to the CYA test, you will need the FAS-DPD chlorine test (which uses a powder plus a liquid reagent). The current DPD chlorine test in the K-1004 can only test FC up to 5 ppm. As you will see on the Chlorine CYA Chart, recommended shock FC levels are considerably above 5 ppm. The FAS-DPD chlorine test can test FC levels up to 50 ppm. You can purchase the individual CYA and FAS-DPD tests here : http://tftestkits.net/Individual-Tests-c6/. If your current test kit is nearly depleted or is more than 2 years old, I would spring for the TF-100 which is a much better buy (http://tftestkits.net/TF-100-Test-Kit-p4.html).

I bought chemicals at Leslie's Pool Supplies, a local chain. The product is called POWER POWDER PLUS and it contains 73% Calcium Hypochlorite as active ingredient. The label also says "Minimum 70% Available Chlorine".

Thanks for this info. If you dosed 1 lb of this product in a 40,000 gallon pool, it should have raised the FC by 2.2 ppm (per Pool Math), so I'm not sure why the test result showed an FC of 5 ppm after dosing. Were any trichlor tabs used in a floater or in-line chlorinator at the same time? If so, that could explain some of the difference.

I'll make another plug for reading the ABC's of Pool Water Chemistry article. It is a quick read that is well-worth your time and it will reinforce the recommendations we are making.

 

[zimm]

Welcome XC marc! These guys are getting you on the right track. Since you test your own water, I highly recommend getting a recommended test kit (see link in my signature). I have the TF-100, a great value. It does the CYA test which you have to have to know how much chlorine you should have in the pool. It also has the FAS-DPD chlorine test which is super accurate, among other things.

That powder pro is good stuff, 73% hypo. A little goes a long way. BUT.... if you don't watch your calcium levels, it could elevate them too much. If you need CH in the water, then the powder is good. We do recommend regular, unscented bleach for the majority of chlorination though, it has no extra chemicals in there.

To answer your question- you need your CYA level, then use the Chorine/CYA chart linked in the above post to find the FC level you need.

If you just want to close 'er down- I'd shock to at least 20ppm and throw in a bottle of polyquat algaecide, and that should hold you for the winter.

Learn from the site here and we'll keep you out of Leslie's and start saving some money...