Inflatable 200GAL Spa - High Ph and TA - Adding Dry Acid - Questions

[amorak]

Hi all

I have a Canadian Spas Grand Rapid small (200GAL) inflatable hot tub. My initial strip test shows high PH (higher than 8.0, which is as high as the strips go... I know, I know) and a 200+ TA count. I've used the tub twice since I filled it 4 days ago, and it's now getting cloudy, so I added 10ppm of DiChlor to shock it (on day 3, after two 30 mins soaks x2 ppl)... I plan to start loading up the CYA to 30 ( at 9 now after first dose last night) and switch to bleach thereafter (the famous method).

I bought some Sodium bisulfate (PH Down) - I was planning on tossing 25g in to drop the PH to around 7.0, let it sit in the tub for 5 minutes, then aerated for 10 minutes or so, then let it sit for an hour and re-test for TA, aerating between dry acid drops to ensure I don't get the Ph below 7.0ish...

Any thoughts on this plan? How best to add the dry acid? I have cheap measuring spoons I bought and I planed to just dump it in the middle of the tub....

I have never had a spa before... I just did a few hours of reading so I feel like I have a 'dangerous' amount of knowledge... ie just enough to make some trouble.

 

[pooldv]

LOL, yes, that plan will work fine. Turn the pump on first.

Have you read the Dichlor then bleach thread? That is how I maintain my tub and it works great. Be sure to add the Borax! it is nice. I like a little epsom salts too.

 

[amorak]

Water was turning green when I got home so I emptied he tub and wiped it down. Refilled with my city water and put in 10ppm of dichlor as it filled. Will work on reducing TA and Ph tonight and then perhaps add a bit more chlorine ?

Does adding the full 30 ppm of Dichlor out once have a problem if I'm not going in for a day or two?

 

[amorak]

So I added 80g of dry acid over a few hours with the jets going to keep the ph from going much below 7.0.

TA in the new water is down to about 120 after that.


Tomorrow I will continue to aerate and add dry acid as I try and get the TA down to ~50 from a starting point of 200+

I didn't add any more dichlor as after 5 hours from new water fill and 10ppm of dichlor the unused, cold tub (12C) is still at 10ppm of FC. So after I add some more dry acid tomorrow night and aerate more I'll keep an eye on the FC as I build up to 34ppm of total dichlor and then switch to a daily tablespoon or two or bleach and a monthly dichlor top up of 5ppm.


Is there a way to calculate how much dry acid I need to add to 800L (210gal) to get it from 120 to 50? Then at least I can count down as I do 40g and aerate for what seems like 20 times.

 

[amorak]

Can someone confirm that for 210 US gallons to reduce TA from 200 ppm to 50 ppm I would need 250 g of dry acid?

That's what I am calculating as my total needed acid additions which means 2-3 days of acid and aeration to get TA down!! Wow that seems like a lot of dry acid - hoping someone can confirm my calc...

 

[pooldv]

Here is the How do I use Chlorine in my Spa (or pool)?.

Are you using PoolMath to calculate your additions? If so, why do you keep asking for someone else to enter the calculations for you? Are you unsure about your entries? We would rather teach you how to use Poolmath than calculate your numbers for you.

At the bottom of poolmath you can enter what if scenarios for what the result would be if you add X amount of something, like dry acid.