Shocking

[Newpoolguy17]

Hello,

I took over operation of our outdoor community pool this year. Took my pool operator course in Feb. still learning about real life chemical use, as it appears everyone has their favourites.

I used up some of of old pool chemicals and a neighbour (who works for a pool company) started restocking for us.

This first time I shocked the pool (with the old stuff- don’t know what it was), I got very good results. Now I’m using something called “capo vinyl shock”. I put 1.4 kg in for our 141,000 litre pool. Just doesn’t seem to have the same effect, btw, our pool is concrete..not sure if vinyl shock is for vinyl pools. It apparently has 34% available Chlorine. What chemical is it exactly? That would help me , but there’s no details on the pail.

To truly shock a pool, do you need to reach breakpoint chlorination? Our health inspector does not require us to test for TC or CC. I thought by shocking, I would see a massive FC spike. But it only went from about 1 to 3 ppm.

So, my questions:
1. Is capo vinyl shock a true shock and is it the right stuff to use?
2. Should FC go much higher after shocking? Should it reach breakpoint?


PS. I use sodium hypochlorite a few times a week to assist the T cell generation.

pH, alkalinity and cyanaric are all in line.

[Denniswiseman]

Shock is just chlorine
Let's have your numbers
FC:
TC:
pH:
TA:
CH:
CYA:
Test strips are commonly called guess strips
You really need to get yourself a decent FAS/DPD test kit (Taylor K2006c or TF Testkits TF100 in the states) to get accurate results as maintaining an appropiate shock level means testing quite often during the day
What model T cell do you have

[Newpoolguy17]

FC: 2.5
TC: 3.0
pH: 7.6
TA: 100
CH:
CYA: 50

I’ve used Capo Vinyl Shock to shock the pool. I put in 1.4 kg per the buckets instructions. I don’t think I reached breakpoint chlorination. The older stuff I used to shock (don’t know what it was) seemed to give greater results.

What’s the chemical in Capo vinyl shock?

[Denniswiseman]

Here's the link to the MSDS http://www.capoindustries.com/wp-content/uploads/2011/09/Pool_MSDS_VINYL_SHOCK-Canada_220211.pdf
Dichlor is the main ingredient
Forget about all the fancy shock and other products. Shock is just chlorine at a large dose
Use these common products to balance your pool
Liquid chlorine (sodium hypochlorite or plain bleach)
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA
I also asked what model T cell you had as there rated output is 24/7 at 100% and may not be large enough to generate enough chlorine
Also for a SWCG you need a CYA of 70 with a minimum chlorine of 3 and a target of 5 with a shock level of 28 as indicated in Chlorine / CYA Chart

[Newpoolguy17]

Our health unit caps CYA at 60.

I use sodium hypo as a supplement to the T cell generator because as you suggest it is not large enough.

So I guess then FC would need to be 24 to slam it?
That means approx 25 Litres of 12% sodium hypochlorite or 5.5 kg of Dichlor if FC is currently 2.5
Wow that seems like a lot.

If I did that at 8pm, would the FC fall to 10 or less by 9am the next day? I can’t open if FC is above 10.

[Denniswiseman]

Our health unit caps CYA at 60.
Refer them to Chlorine / CYA Chart or don't use the T cell and use less chlorine

I use sodium hypo as a supplement to the T cell generator because as you suggest it is not large enough.
So I guess then FC would need to be 24 to slam it?
You don't need to SLAM because your CC is 0.5

That means approx 25 Litres of 12% sodium hypochlorite or 5.5 kg of Dichlor if FC is currently 2.5
Use Pool Maths to work out quantities
Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well

Wow that seems like a lot.
If I did that at 8pm, would the FC fall to 10 or less by 9am the next day? I can’t open if FC is above 10
It may but SLAM stands for shock level and maintain untill you have your CC under control with the overnight chlorine loss test
You can safely swim up to shock level for your CYA