Is Muriatic acid necessary?

[Sjde]

I use Spa Up ( baking soda) and Spa Down in my 375 gallon chlorine spa ( Frog cartridge).
I’ve been having two problems.

Sometimes I have high pH (8) and low alkalinity (below 40). I would use Spa Up to get Alk higher than I wanted , then use Spa Down which dropped both , but dropped pH more than Alkalinity. Is that the only way to do it? The best way?

A few times recently , I balance and then don’t use the spa and check again the next day and the pH has dropped way low- the test color is yellow (7 or lower). I think it may be because we’ve been keeping alkalinity at 40-50. That’s what it seems it wants to be. It was never a problem when we used bromine . And I’ve read if alkalinity isn’t at the correct level, you’ll have trouble maintaining the others.

 

[Texas Splash]

It is true that if your TA gets too low, it can allow the pH to become a bit unstable, but you seem to be doing that yo-yo thing with the two. First, we discourage Spa Down products as they are dry acid and the sulfates in those products tend to cause problem over time. Alk Higher is basically baking soda, so save a few bucks and just use baking soda from the grocery store. Same thing.

As for the pH & TA, only increase the TA enough to keep it from getting below 50. So if your pH is low, increase with with washing soda or just let the jets aeration increase it. When the pH gets too high, only use enough muriatic acid (liquid) to bring it down to about 7.6. If you avoid the really large pH swings, it shouldn't allow the TA to fall too drastically.

Are you using the PoolMath APP to help you with dosage amounts? Perhaps @Mdragger88 has some additional tips.

 

[Mdragger88]

It sounds like You’re on a similar roller coaster as those who use tabs for their pool chlorinating because of the frog . It’s contents are acidic. Think of it as dichlor without the cya.
The mineral portion also has a calcium carbonate binder that is supposed to mitigate this effect . The fun part is that it’s truly a guess at which rate & in what amounts all these things are distributed into the water. Basically, the left hand doesn’t know what the right hand is doing.
The premise of the whole system is to not really know where you stand, trust their little strips, & enjoy a magically maintained spa. Generally when 1 product does many things it doesn’t do any of them well.

To get true control over each parameter & be able to know exactly what is going into your water & how it will react you can follow this guide

How do I use Chlorine in my Spa (or pool)?

If you have a question about any information within this Sticky, please start a new thread for yourself where you will receive very quick responses to your specific questions. Thank you! Introduction There are two main things to consider when maintaining your hot tub water, Water Balance and...

www.troublefreepool.com

& Use PoolMath for calculating amounts.
It is much simpler to test & adjust each parameter individually with separate chems than it is to try to combat/chase the mysterious/ negative effects of a “multi function” product.
The premise of TFP is to only add what you need & can accurately test with a Taylor k2006/tf100.

 

[Sjde]

I use the Taylor 2006 but our hot tub person ( who does it when I’m away from this vacation rental ) uses the Taylor 2005.

I don’t have muriatic acid and was hoping not to have to use it.

I am actually using baking soda, not Spa Up. I forgot I’d gotten a large bag of it and refill the Spa Up container.

I’ve never used an app. I just looked at it and the Calcium looks high . We keep ours at @ 150. I believe we have an acrylic shell, if that makes a difference.

 

[Mdragger88]

150 is totally fine for the ch-
You can also use the old poolmath web page as well. There’s also a link to it at the bottom of every page on this site.

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.

www.troublefreepool.com

Keeping ta in the 50-60 range is fine & will moderate the frequency of the ph rise if you’re manually dosing with liquid chlorine, using a swg, or even using dichlor (since you can use poolmath effectivs of adding before dosing to see how it will effect your ph).
But when you throw in the monkey wrench of the frog’s unpredictable acidic effects it’s hard to know heads from tails or keep up. Thus the roller coaster you find yourself on.
I suspect until you find another way to chlorinate your spa you will be on this ride.
With my ta at 50 my need for acid is intermittent. Maybe once a week or less. My ph hangs out at around 7.6- 7.8 if it rises to 8.0 I lower it to 7.6. This doesn’t affect my ta. I use a drape over swg to handle the bulk of my chlorination after I get to 30ppm cya by using dichlor, at which point I switch to liquid chlorine to replenish fc from long soaks/heavy bather loads. Occasionally I use dichlor to replenish cya often killing 3 birds with one stone- raising fc, lowering ph, raising cya. The difference is that i know exactly what my measured dose will do because of poolmath effects of adding.
You have no idea what the frog is doing or when.
Ps - always follow the FC/CYA Levels

 

[Sjde]

My TA has most often been around 40.