Over Shock Pool

Animal827

Member
Apr 26, 2021
10
East Norwich, NY
Pool Size
16500
Surface
Vinyl
First, I apologize if this thread currently exists.
I have a kidney bean shaped pool at ~16,500 gallons with a DE Filter, inline chlorinator, oil fired heater, and vinyl siding.
I rarely shocked my pool. I typically wait till CCL is above .5ppm. I prefer to use liquid shock (Sodium Hypochlorite).
I have read that under shocking your pool can be bad (e.g., increase chloramines). So, it may seem to better to over shock your pool than under shock. One bad thing I have read is that if you over shock, it will just take longer for the chlorine level to settle.
So, my question is, how bad is it to over shock your pool? For example, if I calculate that my pool needs 1.5 gallon of shock, how bad would it bee to add 2 gallons?
 

Bradrc

New member
Apr 1, 2021
4
Spring, tx

Animal827

Member
Apr 26, 2021
10
East Norwich, NY
Pool Size
16500
Surface
Vinyl
Thanks for the quick response. I was speaking generally, but I have numbers if you like as well.
FCL 2.12
TCL 3.24
CCL 1.12
pH 7.4
Alk 90
CH 174
CYA 74
I am using a LaMotte ColorQ Pro 7. I also have test strips and take samples to pool store. Sometimes I just like to double check that the ColorQ is aligned with other testing methods.
I use liquid Sodium Hypochlorite at a concentration of 87.5%. If my calculations are correct, then about ~1.5 gallons should get reduce my CCL.
I use Trichlor tablets, so I'm constantly fighting CYA. I was just referred to the Chlorine/CYA chart and I always thought you needed to keep FCL at 1-3 maybe 3-5, buy 7-9 seems high. The test kits usually can't test past 10ppm.
In any case, I hope I gave enough information, but I got a spreadsheet tracking nearly everything in my pool for the past 2 years if you want any more data :).
 

Bperry

Gold Supporter
Aug 20, 2020
1,071
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
Thanks for the quick response. I was speaking generally, but I have numbers if you like as well.
FCL 2.12
TCL 3.24
CCL 1.12
pH 7.4
Alk 90
CH 174
CYA 74
I am using a LaMotte ColorQ Pro 7. I also have test strips and take samples to pool store. Sometimes I just like to double check that the ColorQ is aligned with other testing methods.
I use liquid Sodium Hypochlorite at a concentration of 87.5%. If my calculations are correct, then about ~1.5 gallons should get reduce my CCL.
I use Trichlor tablets, so I'm constantly fighting CYA. I was just referred to the Chlorine/CYA chart and I always thought you needed to keep FCL at 1-3 maybe 3-5, buy 7-9 seems high. The test kits usually can't test past 10ppm.
In any case, I hope I gave enough information, but I got a spreadsheet tracking nearly everything in my pool for the past 2 years if you want any more data :).
You might check your chlorine concentration again. It’s probably 12.5%, not 87.5%
 

YippeeSkippy

Mod Squad
Gold Supporter
LifeTime Supporter
Jan 17, 2012
17,725
Evans, Georgia
Animal, puck use will over time raise your CYA level to a point that it becomes very difficult to put enough FC in there to keep algae at bay. We rarely encourage routine puck use and prefer liquid chlorine as it adds nothing but chlorine to the water.

It looks like you've hit your wall- too much CYA. Can you drain your pool down a bit and refill? I know East Norwich probably has a high water table so you should be careful lest the pool floats. Draining - Further Reading

One way you could get away with puck use is by allowing the fall thru spring rains and snow help you exchange water yearly.

How does your water look?? Any visible algae?

Maddie <whose mom was born and raised in your sweet little town>
 

jimbethesda

Gold Supporter
Jul 2, 2018
534
Austin, TX
The test kits usually can't test past 10ppm.
They can, you just need the right one. You need a FAS-DPD chlorine test. It will test as high as you can count.

A FC level of 1-3 was first recommend before the effects of CYA were fully understood. Pool stores and pool service companies have a vested interest in NOT telling you so they can sell you more pucks and magic potions (algaecides, “shock”, etc). Buy a Taylor 2006c or TFT-100 and a SpeedStir. Stick this site. Once you get the hang of it, you will spend less $$ and have a healthier pool overall.

The other concept is “shock” is a verb meaning to bring your free chlorine level to 40% of your CYA level. You are adding a product called “shock” which can be several different things. So by putting shock (the noun) in your pool, you might never have put enough to shock (the verb) it.
 

Animal827

Member
Apr 26, 2021
10
East Norwich, NY
Pool Size
16500
Surface
Vinyl
Animal, puck use will over time raise your CYA level to a point that it becomes very difficult to put enough FC in there to keep algae at bay. We rarely encourage routine puck use and prefer liquid chlorine as it adds nothing but chlorine to the water.

It looks like you've hit your wall- too much CYA. Can you drain your pool down a bit and refill? I know East Norwich probably has a high water table so you should be careful lest the pool floats. Draining - Further Reading

One way you could get away with puck use is by allowing the fall thru spring rains and snow help you exchange water yearly.

How does your water look?? Any visible algae?

Maddie <whose mom was born and raised in your sweet little town>
Thanks! My pool is always crystal clear. I have never had a problem with algae outside opening the pool for the season. This year, the pool was actually clear with little leaves. I usually drain refill about 1/3 or so once it gets to 80 CYA. This brings it down to about 30. Unfortunately, I don't typically work from home, so manually adding liquid chlorine or buying a new chlorination system is not a solution that will work from me at this point. I am not a fan of floaters as they can just get stuck at the stairs or my kids will try to play with it. I chase my CYA with draining, which also causes my water bill to get bigger, but it needs to be done on occasion. I guess what I am hearing here is that shocking is not going to lower my CCL. It seems to have worked in the past so my concern was effects of over shocking. It almost seems like since I have high CYA that I would have to compensate and shock even more.
 

Animal827

Member
Apr 26, 2021
10
East Norwich, NY
Pool Size
16500
Surface
Vinyl
They can, you just need the right one. You need a FAS-DPD chlorine test. It will test as high as you can count.

A FC level of 1-3 was first recommend before the effects of CYA were fully understood. Pool stores and pool service companies have a vested interest in NOT telling you so they can sell you more pucks and magic potions (algaecides, “shock”, etc). Buy a Taylor 2006c or TFT-100 and a SpeedStir. Stick this site. Once you get the hang of it, you will spend less $$ and have a healthier pool overall.

The other concept is “shock” is a verb meaning to bring your free chlorine level to 40% of your CYA level. You are adding a product called “shock” which can be several different things. So by putting shock (the noun) in your pool, you might never have put enough to shock (the verb) it.
I guess my next testing kit will be a Taylor, but after spending $175 on what I thought would be a good digital easier to read test kit and then another $75 on reagents, ill have to feel i didn't just burn my money and get a couple of years out of it 🙃.
 

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IceShadow

Gold Supporter
TFP Guide
Jun 8, 2019
2,612
Milwaukee, WI
Pool Size
20000
Surface
Vinyl
Chlorine
Liquid Chlorine
Sunlight gets rid of CC. FC can stop more CC from accumulating by stopping algae blooms, but the whole “get your FC to 10x CC levels” is unnecessary. Just let sunlight burn off the CC, and keep FC to a level that stops algae from growing.
 

Animal827

Member
Apr 26, 2021
10
East Norwich, NY
Pool Size
16500
Surface
Vinyl
Sunlight gets rid of CC. FC can stop more CC from accumulating by stopping algae blooms, but the whole “get your FC to 10x CC levels” is unnecessary. Just let sunlight burn off the CC, and keep FC to a level that stops algae from growing.
Thanks! Sounds simple enough. Is there invisible algae? I mean can there be algae and I not know it. I have heard of green, yellow, black, but if I don't see algae does that mean my FC is high enough? So the unnecessary part- does that mean it is bad to shock that high? I guess, if I add 2 gallons of sodium hypo to the pool, will that be bad? Cause any damage to pool or just need to wait longer before FC returns to swimming levels?
 

IceShadow

Gold Supporter
TFP Guide
Jun 8, 2019
2,612
Milwaukee, WI
Pool Size
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Surface
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Chlorine
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You have to do the math (or use a calculator like pool math) to see the FC that will add. You would want to bring it up to the high end of the standard range on the FC/CYA Chart and test often (daily to start, but once you get a feel for how much the FC drops daily you can cut it back to 2-3 times a week) and add when your FC gets down below the standard range to bring it back up.

There isn’t invisible algae, but there can be algae hiding where you don’t see it. The safest way to be sure when your water is clear is to do an Overnight Chlorine Loss Test to see. If you don’t lose any overnight with no sun on the pool then you can be pretty sure there’s no algae hiding anywhere. But with 2-3 FC and a CYA of 70-80 you’re flirting with allowing some algae to start showing up.
 
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Soximus

Active member
Sep 28, 2020
42
Connecticut
Pool Size
18425
Surface
Vinyl
Chlorine
Liquid Chlorine
Sunlight gets rid of CC. FC can stop more CC from accumulating by stopping algae blooms, but the whole “get your FC to 10x CC levels” is unnecessary. Just let sunlight burn off the CC, and keep FC to a level that stops algae from growing.
Just want to say, I can't believe this is the first place I've read this info about managing CC! Thank you, Ice. Why on earth wouldn't the Taylor test kit booklet mention that CC could be reduced by doing absolutely nothing... instead, it just told me about the 10x CC thing?! Ack.
 

IceShadow

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TFP Guide
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Pool Size
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Surface
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Chlorine
Liquid Chlorine
I mean the 10x thing might work too? Dunno. Sunlight seems to do fine without bleaching my liner. Even if 10x was the goal, we know CYA disrupts the hypochlorous acid, so…who knows!
 

YippeeSkippy

Mod Squad
Gold Supporter
LifeTime Supporter
Jan 17, 2012
17,725
Evans, Georgia
As a nurse who dealt with ventilators and patients with breathing problems, I equate pool water to respiration. The pool bubbles that cause your pH to rise are just like breathing- it is an exchange of acid and oxygen.
If I leave the autocover on that exchange isn't happening as much as it should. I've trapped those CCs under the cover. But give the water a few hours of sunlight and fresh air and my CC level goes down.

When your CYA level is too high, too much of your FC is bound to it and there isn't enough available to chew thru your contaminates. Hence you have higher CCs. Sunlight isn't going to solve the problem of contaminates, only more Free Chlorine will do that.

Maddie :flower:
 
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