Confused newbie

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
shward1
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My Pool: 3 person spa, 180 gallon capacity

Confused newbie

Postby shward1 » Mon 12 Aug, 2019 20:04

My wife and I purchased a new spa about a 5 weeks ago. This is our first spa and we are very much enjoying it. It is a smaller 3 person spa with a water capacity of 180 gallons.

We filled the spa the spa with city water and we have both been in it an average of 4 days each with for ~30 mins each of those days. We have used the following chemical regimen based on the spa dealers advice -

- After fill up ran jets for 1 cycles (15 mins)
- Added 1/2 cup of SPA UP and ran jets for 1 cycle
- Added 1/2 bottle of SPA MARVEL
- Waited 24 hours then added 1/2 bottle of SPA MARVEL
- After each use added 1/4 cup of non-chlorine shock
- Once a week added 1/4 cup of chlorine
- After 4 weeks added 1/4 cup of SPA UP

I was told with this continued regimen I would not need to test the water chemistry and all would be good, having no spa experience I did not question this.

Throughout the entire time we have had the spa the water has been pleasant, mostly clear with a very little bit cloudiness the last week and no foul smell at all.

About 3 weeks in my wife started to develop a rash on her chest.

After doing some research I purchased what seems to be a good test kit, a LaMotte ColorQ Pro 7. My initial tests yielded the following results, this was just a few hours after adding the chlorine -
FCL: 9.87
TCL: Hi (beyond meter limits)
pH: 7.9
ALY: 184

I continued to get very similar numbers over a the next couple of days.

My research indicated (right or wrong) that I should tackle the alkalinity first, and I decided to go the muriatic acid route. I purchased some acid from the local hardware box store which is 14.5% and did the following -

- Added 1 ounces and ran jets/air for 30 mins --> pH: 7.7, ALY:165 (the acid seemed to do it jobs)
- Added 2 ounces and ran jets/air for 30 mins --> pH:7.5, ALY: 169

When adding the acid I filled a 2 gallon pale with spa water and added the acid to it. After a good mixing I poured the mixture into the spa slowly with the jets running and the air off.

It was my understanding that adding acid would have a very deterministic result given all other things being equal. Why did the 2nd dose of 2 ounces not lower the alkalinity as expected?

Thanks in advance for guidance...

Shane


Denniswiseman
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Location: United Kingdom

Re: Confused newbie

Postby Denniswiseman » Tue 13 Aug, 2019 03:17

Hi Shane and welcome
Forget about TA for the moment, how are you chlorinating, stabilised chlorine or liquid chlorine?
What is the limit of your TC because it seems you have combined chlorine which could be causing your rash
The acid would have reduced your TA I can only assume that it was an error in testing
shward1
I'm new here
I'm new here
Posts: 5
Joined: Mon 12 Aug, 2019 19:24
My Pool: 3 person spa, 180 gallon capacity

Re: Confused newbie

Postby shward1 » Tue 13 Aug, 2019 12:25

Thanks for the response Dennis.

I am chlorinating with dichlor.

The test kit has a TC range of 0-10ppm. A TC test yesterday showed a TC of ~3.

Thanks,

Shane
Teapot
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Location: UK

Re: Confused newbie

Postby Teapot » Tue 13 Aug, 2019 15:47

If I may add, the use of non chlorine shock (peroximonopersulphate) is known to test as combined chlorine and as the level rises cause hot tub rash. mono persulphate can last around 2 weeks so don't add anymore, keep using chlorine only, what is the CYA stabiliser reading as this will set the level you should be running the chlorine at.

The different chemicals in the pool, monopersulphate and what ever the other stuff is can interfere with test results.
Use liquid chlorine - bleach for chlorine source. acid for pH adjustments and lowering Alkalinity but the air jets will also cause the pH to rise (you should never need spa up!) just a shop selling you more stuff you do not need.
You have a good tester, stick to that and Dennis and I and you won't go far wrong!
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 1262
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Confused newbie

Postby Denniswiseman » Tue 13 Aug, 2019 16:31

shward1 wrote:Thanks for the response Dennis.

I am chlorinating with dichlor.

The test kit has a TC range of 0-10ppm. A TC test yesterday showed a TC of ~3.

Thanks,

Shane

AsTeapot says it's best to use liquid chlorine (plain bleach) excessive CYA renders your chlorine ineffective
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
It may be more sensible to dump your existing water and rebalance with these common products
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
shward1
I'm new here
I'm new here
Posts: 5
Joined: Mon 12 Aug, 2019 19:24
My Pool: 3 person spa, 180 gallon capacity

Re: Confused newbie

Postby shward1 » Tue 13 Aug, 2019 19:23

Great advice and I am learning a lot!

Here are my current readings, I haven't used the tub or added any chemicals for 48 hrs -
FC: .75
TC: 8.86
pH: 7.9
ALK: 149
CYA: 87

I do plan to dump the current water soon, but am curious how I should interpret the current numbers and what steps I would take to hit target numbers?
shward1
I'm new here
I'm new here
Posts: 5
Joined: Mon 12 Aug, 2019 19:24
My Pool: 3 person spa, 180 gallon capacity

Re: Confused newbie

Postby shward1 » Tue 13 Aug, 2019 20:19

Am I correct that an FC of .75 and TC of 8.86 is not good? Is this what is referred to as "chlorine lock"?
shward1
I'm new here
I'm new here
Posts: 5
Joined: Mon 12 Aug, 2019 19:24
My Pool: 3 person spa, 180 gallon capacity

Re: Confused newbie

Postby shward1 » Tue 13 Aug, 2019 21:10

Teapot and Dennis: The more I research the more your information and guidance start to make sense to me!

I've been using the non-chlorine shock on a regular basis. If TC = FC + CC, and non-chlorine shock tests as CC, my low FC and high TC adds up.
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 1262
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Confused newbie

Postby Denniswiseman » Wed 14 Aug, 2019 06:23

The CYA is high try getting it to 40-50 and the Chlorine / CYA Chart will show you where your chlorine should be
pH is a bit high but if the spa has bubbles that would raise it, try lowering your TA and see if that helps
I would be inclined to dump your water of only 180 gallons and start again using the basic products previously documented
You can use your stabilised chlorine to get your CYA up to a sensible level

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