New pool, good water test, do I really need to shock?

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J

JSlabotsky

Active member
Jul 28, 2014
32
Piedmont, OK
We are on week 3 after opening our new vinyl pool. In order to keep in good standing on the warranty from the pool builder, I've been having them test my water weekly and following their recommendations.

Week 1 - Added 2 gallons muriatic acid, 2.5 pounds of shock powder
Week 2 - 2 more gallons acid, 2.5 lb. shock, 5 lb. stabilizer (sock method)

Now at Week 3 they are recommending I shock it, despite the fact that the numbers all fall within their recommended ranges.

FC = 3.68 (2-4 recommended, seems low, but that may be because we have an ozone generator)
TC = 3.96
CC = 0.28
pH = 7.4
CH = 238
TA = 108 (week 1 was 220, week 2 was 170)
CYA = 44

It all looks pretty good to me. I have been using trichlor pucks in the chlorinator. It ran out for about half a day and I replenished it, so FC may go up a little from where it is right now. Right now the auto chlorinator is on the highest setting. Then again, I had the solar cover on for a few days, so this weekend we may burn off some FC in the sun. Looking at highs in the upper 90's and our pool is in full sun until late evening.

So do I really need to put shock in it again this week? They advocate weekly shocking, but intuitively this seems unnecessary unless you're having trouble keeping the numbers in line.
 
I would not put any more pucks or powder shock in that pool. With a CYA of 44 (which may or may not be accurate, I can tell you aren't using the opacity test), you are approaching your limit, and you may have additional CYA in the pool that hasn't registered yet.

Since you are at the mercy of the pool builder for warranty, I would follow their advice and shock the pool with liquid chlorine per their instructions.
 
Those were their numbers using a WaterLink DataMate 10. My Taylor K2006 test kit came yesterday. I plan on doing my own test tonight or tomorrow to see how they line up.

I've looked at a number of articles here on the site and nothing gave me the impression that a CYA of 44 was close to the limit. With that said, I'll turn off the chlorinator and make all my adjustments with bleach for the time being. With the temperatures we're expected to have over the next several days, there may be enough evaporation to merit adding new water to the pool. That should bring CYA down at least a little bit, right?
 
RobbieH said:
I would not put any more pucks or powder shock in that pool. With a CYA of 44 (which may or may not be accurate, I can tell you aren't using the opacity test), you are approaching your limit, and you may have additional CYA in the pool that hasn't registered yet.

Since you are at the mercy of the pool builder for warranty, I would follow their advice and shock the pool with liquid chlorine per their instructions.
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Yes.

Get that test kit out and get your own numbers!

A pool at CYA 50 is a little easier to manage than CYA 70. After that it gets a little more challenging... (and you're headed there quick with trichlor pucks!)
 
The recommendation for CYA is 30-50 for non-salt water pools which it appears is what you have. With that said and the lack in faith of pool store CYA testing accuracy I would not add any chlorine but bleach until you do your own CYA test and verify what it really is. Also, the only way to reduce CYA is by replacing water by draining or splash out, evaporation does not remove CYA.
 
JSlabotsky said:
Those were their numbers using a WaterLink DataMate 10. My Taylor K2006 test kit came yesterday. I plan on doing my own test tonight or tomorrow to see how they line up.
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:cheers: I love it when people already have the proper kits on order before they post. Really gives me the impression you have done some homework. seriously pat yourself on the back.
JSlabotsky said:
I've looked at a number of articles here on the site and nothing gave me the impression that a CYA of 44 was close to the limit. With that said, I'll turn off the chlorinator and make all my adjustments with bleach for the time being. With the temperatures we're expected to have over the next several days, there may be enough evaporation to merit adding new water to the pool. That should bring CYA down at least a little bit, right?
Click to expand...
Yes and no. the CYA doesn't evaporate with the water...so when the water leaves by evaporation you could say the CYA level increases, then when you add water back in it returns to its previous level. The only way to really lower CYA is to drain off water and replenish with fresh.
 
What do we have here? A person that has read TFP stuff AND ordered a good test kit?????? Where did you come from and can we get some more? LOL

Great job! You are thinking right in that you should not "shock" the pool with powder shock. If they want you to keep the FC level up do so with liquid chlorine.

Talk to them about what they are looking for when they want you to shock the pool weekly. Are they telling you to do this to keep the FC up? With what you know you can tell them what you will do using your knowledge from TFP to make them happy and keep your warranty intact.

Good luck and please post a pic of your new pool. We LOVE pics!

Kim
 
Thanks for the replies and encouragement. I'm a huge nerd, as my wife will attest, so I always go nuts analyzing and researching stuff. I'm "that guy" who reads the owner's manual from front to back every time I buy a car. :rolleyes:

Good to know that CYA does not evaporate. Knucklehead builders didn't plumb a valve that pumps water out to waste (and no backwash since I have a cartridge filter). I'll have to look at fixing that. I'd been reading about how the powder shock adds CYA, so that's what prompted me to post before doing it again.

I'll probably have to get hold of the store manager to find out what they're looking for. The young gal who usually tests my water seems to only know how to recite what she's been told. If I start asking questions prompted by stuff I read here, she gets kind of nervous and stumbles over her words. [EDIT] Based on past conversations, I think keeping FC level up is probably the reason they recommend it. [/EDIT]

The printout from their computerized system says the reason for shocking is to eliminate combined chlorine. Is that really what shock does? I thought all it did was add more FC.
 
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Shocking is to quickly add enough FC to kill any organics in your water. That's why most of us here don't need to regularly "shock" our pools. Any solid form of chlorine will add something that you will need to control-- Trichlor and Dichlor will both add CYA and cal hypo will add calcium both of which are good to have, but only to a point--30 min to 50 max cya for a non-swg pool. I don't know much about calcium except for leslies trying to tell me I needed to raise mine a bunch every time i saw them.
 

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FC becomes CC when it's in the process of killing something. If there is CC, it means you have things alive in your water, "organics" as we say. Not sure I just used 100% accurate terminology, but that's the gist of it.

With proper levels of FC, you should never have much needing to be killed, so your CC will remain low, and you will not need to ever shock. I believe anything less than .5 CC is essentially considered to be zero...and personally I would NOT shock based only the numbers from that water test.

Weekly shocks is a (expensive) way to make up for not properly managing pool chemistry, which it sounds like you are prepared to properly manage with little bit of education from this site.

Good job on getting an accurate test kit. That's step 1.
 
peterdaly said:
I believe anything less than .5 CC is essentially considered to be zero...and personally I would shock based only the numbers from that water test.
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I'm confused.. my CC is below .5 (currently .28). Are you saying this particular test indicates I should go ahead and shock? Or are you saying you would only shock when a water test indicates it is necessary (e.g. CC is above .5)?
 
I THINK what he means is that he would only shock "based only on the numbers from THAT water test" as in only IF the numbers of your tests show you need to SLAM. No need to SLAM/shock just because that is what everyone else does because they do not know about TFP.

With a TC of .5 or less you do not need to SLAM so long as the water looks good.

Kim
 
Thanks for the clarification.. I wondered if a "not" was missing. The ozonator was a gimme that I didn't really care about. Honestly I haven't been running it most of the time because of what I've read here. However, I was tempted to run it for a while and see if it brought down the CC. That said, I think we'll have plenty of sun the next few days.
 
Alright, I tried out the Taylor test kit for the first time. I did each test at least twice to make sure I counted the drops correctly, etc.

FC = 5.6
CC = ~0.2 (closer to .2 than .4)
pH = 7.4
CYA = ~45
TA = 130

On the FC... I took the sample that went to the pool store at 7:00 AM, but it wasn't tested until 11:45 AM. It was kept indoors (took it to the office with me), but maybe the time lapse accounts for the lower number? Also, the auto chlorinator was just refilled the night before and ran wide-open all day today, so the level in the pool really could have risen a little throughout the day. In addition it was cloudy a good part of the day. I turned the chlorinator off around 7:30 PM and will retest FC in the morning.
 

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