low TA high pH; please help

[mkinsocal]

OK - noob here, trying my best to get my spa in order.

first, the setup:
850 gal in ground pebble spa with waterfall
Chlorine from SWG
Water is usually kept at whatever temp then sun makes it (73-80 this month); We'll bump it up to 90 to use it (the kids don't like it much hotter than that) and currently we're only using it about once a week.

Now the problems:
TA = 70; pH = 7.8, CH = 320
I've had the TA up to 90, but have been unable to lower the pH. As I try to lower the pH, all it does is reduce the TA, so now it's back to 70 with only minimal reduction in pH. I'm going to add baking soda to bring the TA up, but my fear is that this is going to raise the pH again. At first I thought pH is not coming down b/c I've been using some older muriatic acid (years old from my parent's pool) but it's been stored indoors, sealed; I read that MA doesn't really "expire"; plus the TA is coming down, so I assume it's working. And it burns if I accidentally get a whiff of it

As an aside, I'm also trying to lower my chlorine a bit - my SWG was set at 80% (running only when the fliter runs (from 0900 - 1700)). Chlorine has been running around 7 ppm. I've now reduced the SWG to 55% and really no difference in chlorine reduction. I did turn off the SWG for a day and my chlroine when to zero. Now that air temps have dropped from 95 to 70, I realize Cl is not being used as much, but any tips in getting the Cl down to 3 range (just keep reducing the % it's running???). I haven't tested CYA yet - getting ready to do that today.

Thanks for your help. This seems like a great forum.....

 

[poolsupplysales]

When you add muriatic acid to lower the ph you must walk around the pool when adding, to lower total alkalinity you add acid in one spot in the middle of your spa. Keep in mind it is difficult to keep the ph down in a salt water pool due to the fact salt is a base. As far as getting the chlorine down keep reducing the % a little at a time untill the level is stabalized. It is not the air temp that burns off the chlorine but the uv rays of the sun. Hope this helps you

 

[PJ]

Well you have two problems....1) the water fall will keep raising your ph no matter what you do...and so will the chlorine generator in most cases. 2) the generator continually produces chlorine when the pump is running....at the same rate it is set at regardless of use.
My advice would be to raise your TA to around 110 using baking soda and to lower your PH using acid little by little as it rises. You will have to continually repeat this process, unless you can shut off the waterfall when not in use. Also you will have to adjust the clorine production level based on user load. As far as I know it is not ok to use CYA in any spa....otherwise that combined with the turning on/off of the pump would be the answer to holding your chlorine steady.

 

[imrodee]

@mckins - I've been told that you could be getting a false reading on your pH if your FC is over 10. My FC was up at shock level. I am working on getting that down today.

Good luck! You'll get lots of good advice in here.

 

[chem geek]

My advice would be to raise your TA to around 110 using baking soda and to lower your PH using acid little by little as it rises.
:
As far as I know it is not ok to use CYA in any spa....otherwise that combined with the turning on/off of the pump would be the answer to holding your chlorine steady.

When the pH tends to rise you do NOT want to raise the TA level since that will only exacerbate the problem by increasing the amount of carbon dioxide outgassing that will further raise the pH. If one cannot reduce the aeration sources, then one can use another pH buffer such as 50 ppm Borates to slow down the rate of rise. I think that's your best bet -- get the TA lower and add boric acid for borates. If your spa were acrylic/fiberglass instead of pebble (which I presume has calcium carbonate between the pebbles), then you could have the TA be even lower at 50 ppm. See Water Balance for SWGs.

As for covered spas, you still want to use CYA in a spa, but at a low level such as 30 ppm. If you don't, then the active chlorine level will be too high and will outgas faster, oxidize swimsuits, skin and hair faster, degrade covers faster, corrode metal faster, create disinfection by-products faster, etc.

 

[PJ]

I do know that most spa makers specifically say not to use stabilizer, unless you want your warranty to be void.....check your owners manual if available.

 

[PJ]

I also have no experience with borates, I am just going by my experience with salt water hot tubs....all of which were not connected to a pool.

 

[y_not]

@mckins - I've been told that you could be getting a false reading on your pH if your FC is over 10. My FC was up at shock level. I am working on getting that down today.

Good luck! You'll get lots of good advice in here.

Imrodee, that is correct. Only test pH at or below 10ppm FC.

I do know that most spa makers specifically say not to use stabilizer, unless you want your warranty to be void.....check your owners manual if available.

I can't even imagine why they might say this, it really makes no sense whatsoever. I would use it anyway, more CL is required without it and it's not like they can tell if you use it anyway. Not unless you tell them you used it as I doubt that if there even were enough trace residue for them to detect it on the exposed surfaces and plumbing, that I doubt they'd even bother with it.

 

[jblizzle]

When you add muriatic acid to lower the ph you must walk around the pool when adding, to lower total alkalinity you add acid in one spot in the middle of your spa.

This so-called "slug" method is not true and has been disproved and likely to damage the pool/spa surface. Always add acid slowly in front of a return so it mixes immediately.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[y_not]

When you add muriatic acid to lower the ph you must walk around the pool when adding, to lower total alkalinity you add acid in one spot in the middle of your spa.

This so-called "slug" method is not true and has been disproved and likely to damage the pool/spa surface. Always add acid slowly in front of a return so it mixes immediately.

Posted from my Droid with Tapatalk ... sorry if my response is short

Thanks Jason, my thoughts exactly. I was thinking, uh, acid is acid. I thought he was saying that depending on how you add it you get different effects on TA and pH, seemed so wrong.

Now I know that he was talking about slugs vs liquid acid.

 

[mkinsocal]

Thanks so much for everyone's advice.
Just a few things to clarify:
1) the waterfall, jets and filter are on three seperate pumps, so can be run independently. The waterfall is only on once a day for about 5 minutes, just to circulate the water through the pump, then it's off. I'll usually turn it on at night while we're eating dinner or something, but most of the day it's off. So I don't think that's increasing the pH too much.

2) The Chlorine is below 10, so that shouldn't be affecting the pH reading; however, I clearly don't need to be running the SWG as much as I am, so hopefully by reducing it (I dropped it to 45% today) that will help.

3) This is a built in, free-form in-the-ground spa, not a pre-fab; so I agree, I'm not sure why CYA would adversely affect anything. It's basically just a small pool from that standpoint (although I realize I want it balanced differently than a pool.....). I didn't get around to testing it today, but my guess is that there's not much stabilizer in it.

So given all of that, I'm down to two different recommendations here - one is to increase the TA to 110 and then add acid to bring down the pH; the other is to tank the TA to some low number and use borates (I haven't read up on borates, but if I can avoid adding another chemical to my spa, I'd prefer just to keep things simpler; but if I need to, I will). Anyway, if I could get a few votes on those, I'll give it a try (or if someone has another option I'm all ears)

thanks again!

 

[jblizzle]

When you add muriatic acid to lower the ph you must walk around the pool when adding, to lower total alkalinity you add acid in one spot in the middle of your spa.

This so-called "slug" method is not true and has been disproved and likely to damage the pool/spa surface. Always add acid slowly in front of a return so it mixes immediately.

Posted from my Droid with Tapatalk ... sorry if my response is short

Thanks Jason, my thoughts exactly. I was thinking, uh, acid is acid. I thought he was saying that depending on how you add it you get different effects on TA and pH, seemed so wrong.

Now I know that he was talking about slugs vs liquid acid.

Actually the "slug method" uses liquid acid. The theory was that putting it in the water in different ways caused different results. There is a thread about it with pictures somewhere on here. Total bunk.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[chem geek]

I do know that most spa makers specifically say not to use stabilizer, unless you want your warranty to be void.....check your owners manual if available.

This makes no sense. Most residential spas use Dichlor as the source of chlorine and Dichlor increases CYA (stabilizer). I believe what you may be referring to is that some spa makers say that TDS or salt levels cannot be high, as would be needed for saltwater chlorine generators. Some may limit this to 1500 ppm or else the warranty is voided. This is to prevent corrosion in spas using materials that aren't as resistant to higher conductivity water. Or perhaps you are referring to some states where no CYA is allowed in commercial/public spas or indoor pools. Such regulations do not apply to residential pools or spas and have nothing to do with spa makers or spa warranties.