Hot Tub Start Up Questions

[hansn484]

Problem: Keeping my TA at 50 causes pH to raise to over 8+. pH was only in 7.6 range when my TA was LOW(20 ppm).

I'm following the "How do I use Chlorine in my Spa" instructions for the first time(I was using frog ease prior). This is after a drain, scrub the tub, and refill with my hose water(which does run through my water softener).

Initial readings were(Test kit TF-100 for PH and Chlorine and FAS-DPD K-2006 for TA -- I'm using two because I had the K-2006 first and am using the reagents up.):
TA - 170
pH - 8+
CH - 0

First, I got the CH up to 130 - all was good. pH was still high. TA 150-160.

I moved on to the method to reduce pH to 7.0 then aerate back up. I was adding sodium bisulfate to lower the pH. The thing is within 10 minutes of adding the acid, the pH was back over 8+. I didn't think anything of it and kept adding acid, waiting 10-15 minutes, repeat - until the pH finally got low. By that point the TA was down to 20 ppm. pH was 7.6-7.8-ish.

I looked and read on this forum that 20ppm is too low, so I tried to raise it back to 50ppm(per instructions). When I do that the pH goes back over 8+.(It does not land at 7.6 like the instructions say.)

Now I'm a bit lost on how to proceed.
Do I accept the low TA so I have a good pH?
Drain and refill again? (Perhaps some of the frog ease chems were still left over?)

Any advice?

Thanks in advance. Been a long time follow of BBB for my pool.

Hot Tub details:
South Seas Spa 735B
360 gal

 

[santacruzpool]

Are you using Sodium Bicarbonate? That is good for raising TA if it is too low - not really for pH control.

You should be using Muriatic Acid to lower the pH and lower the TA - aeration will cause the pH rise until you get to a lower TA - so you will need to do MA additions and aeration cycles several times to get the TA down - IF it is higher than 50. You should find things get stable when TA is closer to 50. I find my spa only gets stable when the TA gets down to 40-50.

Below is from a prior post by @duraleigh
pH up - 20 mule team borax (TA comes up to)
pH down - Muriatic acid
TA up - Baking soda (pH doesn't come up much)
TA down - aeration and acid...it's process found in Pool School that you must read to make TA change quickly and permanently.

 

[jseyfert3]

When you test TA, when are you stopping the test? Many people, myself included at first, tend to stop when the green vanishes or at the first hint of red. Keep adding drops until a drop doesn’t change the color further, then subtract that last drop from your count.

I find I always need one drop, usually two extra drops after the first hint of red. That could take what you thought was 20 and make it a reading of 40, which I would say is fine.

 

[hansn484]

Are you using Sodium Bicarbonate? That is good for raising TA if it is too low - not really for pH control.

You should be using Muriatic Acid to lower the pH and lower the TA - aeration will cause the pH rise until you get to a lower TA - so you will need to do MA additions and aeration cycles several times to get the TA down - IF it is higher than 50. You should find things get stable when TA is closer to 50. I find my spa only gets stable when the TA gets down to 40-50.

Below is from a prior post by @duraleigh
pH up - 20 mule team borax (TA comes up to)
pH down - Muriatic acid
TA up - Baking soda (pH doesn't come up much)
TA down - aeration and acid...it's process found in Pool School that you must read to make TA change quickly and permanently.

Thanks for your reply. I meant sodium bisulfate.

 

[hansn484]

When you test TA, when are you stopping the test? Many people, myself included at first, tend to stop when the green vanishes or at the first hint of red. Keep adding drops until a drop doesn’t change the color further, then subtract that last drop from your count.

I find I always need one drop, usually two extra drops after the first hint of red. That could take what you thought was 20 and make it a reading of 40, which I would say is fine.

I'll give this a try and see if that helps. Thanks!

 

[santacruzpool]

I would get Muriatic Acid instead of using dry acid (sodium bisulfate) - less chance of damage to your heater and any other metal parts in the hot tub.

 

[hansn484]

When you test TA, when are you stopping the test? Many people, myself included at first, tend to stop when the green vanishes or at the first hint of red. Keep adding drops until a drop doesn’t change the color further, then subtract that last drop from your count.

I find I always need one drop, usually two extra drops after the first hint of red. That could take what you thought was 20 and make it a reading of 40, which I would say is fine.

This worked! Thanks.
@santacruzpool -- Where do I get Muriatic acid? I see one at HD but it's a "Green" Muriatic acid.
Thanks everyone.

 

[jseyfert3]

This worked! Thanks.
@santacruzpool -- Where do I get Muriatic acid? I see one at HD but it's a "Green" Muriatic acid.
Thanks everyone.

Most any hardware store. Green, also known as low fuming, is a lower percentage of acid. 15-20%. Full strength is just over 31%. Full strength acid fumes, which means it produces some acid vapor above an open container. The lower strength stuff does this a lot less.

For a pool most people get full strength for cost reasons, for a hot tub the amount used is low enough that the cost isn’t really an issue, and many may prefer the green/low fuming stuff.

 

[Mdragger88]

Your signature shows that you have a pool also- you should be using Muriatic acid for both. Home Depot & lowes sell it in a 2 pack (2 gallons together in a box) in the pool area for quite cheap. Depending upon your use that could last u a year or two- it does me.

 

[santacruzpool]

I use the 14.5% stuff - it isn't as powerful as the 31% but for a hot tub you need so little it isn't a big deal, and is a little easier to handle. I can't buy the strong stuff at my Home Depot anyway so I stick with the low percentage stuff. I buy the two gallon HDX packs at Home Depot....