Can’t raise TA in saltwater pool

[JTA]

Hello everyone, I am new to the forum and I’m looking for some help.

I am on the central coast of California, City of Arroyo Grande to be exact. I have an inground concrete freeform saltwater pool approximately 25,000 gallons. Attached spa is approximately 1500 gallons. It’s February so the pool is not being used, however, we heat the spa about every week or two for the fam to enjoy.

I am having a difficult time increasing TA.

Current pool chemistry stands as follows…
PH 7.6
TA 50 PPM
Free chlorine 1-2 PPM
Calcium hardness 500 PPM
Salinity 3200PPM

This time of year the pool temperature fluctuates between 52° and 55°. I have removed the in salt chlorinator and installed the dummy cell. I am currently using the Pentair 320 chlorine feeder with 3” tablets (which is fairly ineffective I have found, even using the top feeding plug. But that’s another issue. I maintain free chlorine by adding standard bleach to maintain 1 or 2 ppm)

I am trying to increase TA to about 100 or 110. I use baking soda to increase TA. However, because it is a saltwater pool, pH rises very quickly. I add approximately one half to 1 gallon of muriatic acid weekly in order to lower pH and maintain 7.4 to 7.6

Adding this much muriatic acid of course lowers TA. So I am now in the battle of needing to increase TA while lowering pH. I buy the large 13 pound bags of baking soda from Costco and dump the whole thing into the pool. That raises the TA for a couple weeks. However, I then continue to add muriatic acid to lower pH, which in turn lowers TA again. The pool is incredibly clear and clean and I feel the pool is being sanitized properly even though the PH and TA are not at ideal levels.

I have only had the pool for approximately a year and a half. I don’t recall having this much difficulty maintaining 7.4-7.6 PH and 100-110 PPM TA during the swimming season while using the salt chlorinator. I’m not sure if that is a factor.

I’d love to hear everyone’s suggestions on maintaining my pool chemistry. I am open to any suggestions and willing to completely change my mode of operation if necessary.

An interesting side fact (not sure if this is of any relevance but I figured I would lay it all out on the table) is that I am on well water. My well water has been tested to have 40 to 50 ppm calcium hardness. However, as stated before, the pool calcium hardness has increased to about 500 PPM since it was originally filled about a year and a half ago. When we originally filled the pool it was obviously 40 to 50 ppm calcium hardness because it was filled directly from our well. I’m not sure what is increasing the calcium hardness in the pool water considering the auto leveler water input is from our well water that has low calcium hardness.

I know this is a lot of information to digest but I welcome any suggestion anyone is willing to push my way.

Thanks in advance for your help!!

[Kris79]

Have you checked the calcium content in your well water in recent times ? May be it has increased since the time you last checked and that is what might be causing the hardness in the pool.

[Teapot]

Complicated, if your well water is low in hardiness at 50ppm the water can scavenge the additional calcium from the pool wall structure. Not a real issue if the hardness 500ppm unless you are getting scale deposits?
Yes salt chlorination tends to cause a pH rise but do not believe the pool industry on TA levels, if your pH is reasonably stable at 50ppm TA leave it there. If you add bicarb to try and get it to 110 you'll then start adding pH- to bring your pH in range which will lower your TA again so you'll add bicarb again and repeat the cycle over and over. To reduce any worry you have hard water, and run the pH a little higher at a point where it is stable pH 7.8 for example. What we do need to know is the CYA level in your water, this is the most important level so please record it and come back.

[JTA]

Ok, soooo, my CYA is zero. I’ve never added a stabilizer. Now, before I get laughed out of this forum or receive a bunch of hate mail for being a moron, I will put a slight bit of blame on my last pool maintenance technician. This is the first pool I have owned and installed it about a year and a half ago. The pool tech I was using when we first finished the pool explained to me that because we were running a variable speed pump 24 hours per day at low RPM (about 1900 GPM) for filtration, the salt chlorinator would continually produce chlorine so I therefore did not need to worry about cyanuric acid.

However, now in hindsight, I see that not having a stabilizer is probably not the best idea considering the fact that I remove the salt chlorinator around December when the pool temperature drops below 60° for a couple months. Maybe that’s why my gut feeling was to fire him after about 6 months and take care of pool maintenance myself, lol!!

So now back to business… Regarding your first question about calcium deposits, I have a some around the waterline. However, nothing that is that horrible that I can’t use a pumice stone to remove once per season. When you mentioned Calcium hardness can be scavenged from the plaster, will that continually happen or will it slow overtime? Again, the pool is only a year and a half old. Shall I expect calcium hardness to continually be scavenged out of the plaster or is it spiking because the pool is new?

TA appears to be stable around 50 ppm. I will leave it there and use less muriatic acid thereby keeping pH slightly higher at 7.8.

Now regarding CYA. Would you recommend liquid or granule? And the quick research I did recommended a slightly higher ppm for a saltwater pool, in the area of 70 to 80?

Thanks for your input so far. Looking forward to your response.

[Denniswiseman]

You say your CYA is zero but if you have been using pucks or granules you will be using Trichlor or Dichlor both contain CYA
Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
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
To reduce your CYA you have to do a partial drain and refill
Continuous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well

[JTA]

Denniswiseman, I have no idea what you just said. My free chlorine is no where near 10 ppm. It’s around one or two. Wouldn’t 10 ppm be dangerous to swim in?

[Teapot]

Hi, what Dennis means is for using pucks which contain CYA, say every 3 pucks is 10ppm of chlorine (not all at once, maybe 1 a week, after the 3rd week you'll have 6ppm of CYA).
CYA granules take up to 2 weeks to dissolve, liquid is much quicker obviously.
Granules often put in the flow on the return side in one of your other halves stockings, just make sure she takes it off first!

[JTA]

Ok, I understand what Dennis is saying now. But am I right in that my CYA level should be around 70-80 PPM? If that is the case I’ll obviously need to add CYA as opposed to simply relying on the small amount of CYA that would come from the chlorine pucks. And like I had said before, my chlorine feeder does not seem to be all that efficient in maintaining my FC levels so I resort to just adding bleach.

Either way, it’s only 3 or so months that I use the pucks and/or bleach. The majority of the year the salt chlorinator does its thing.

So back to my original post, I can keep TA at 50ppm, I’m not going to worry too much about calcium hardness at 500ppm. I can always drain and refill a little bit if needed to lower that. And I’ll maintain ph at a slightly higher 7.8 to combat the slightly high calcium level.

Teapot, you said knowing my CYA was the most important level. Now that you know it is zero (I tested it and it is definitely zero) what would having my CYA at 70-80ppm do for my overall chemistry?

[Denniswiseman]

if you look at Chlorine / CYA Chart it will tell you how much chlorine is required for a CYA of 70/80 in a salt water pool
Place CYA granules in a sock and suspend near a return to dissipate it
Pucks have their place for when you aren't able to maintain a chlorine level (vacation)

[Teapot]

Teapot, you said knowing my CYA was the most important level. Now that you know it is zero (I tested it and it is definitely zero) what would having my CYA at 70-80ppm do for my overall chemistry?

Ok, so with 0 CYA your chlorine is burned up by the sun completely in around 4 hours, this means your cell is working overtime to keep producing chlorine which will shorten its life span ( cells have a finite life before they need replacing) The power supply inside the chlorinator is also working overtime, so you now see how misinformed your ex pool guy was.
Back to the chemistry, bicarbonate of soda makes a buffer solution in the water to resist pH change, unfortunately the buffer is around pH 8.1- 8.3, a bit too high hence why using less bicarbonate and therefore lower TA reduces the strength of the buffer and allows the pH to be a bit lower. Now CYA in the water is also a buffer solution but in the lower range of around pH 6.8, so helpful to bring the pH down a little from the bicarb pH. That said CYA isnt strong enough at the usual pool levels of TA (120 ish) to have a major effect but as the TA is lower at 50ppm the pH will move much much easier so if you need to add acid you will only use a small amount, my TA is around 45 and I haven't added any acid (pH- ) in 3 years.
You may have to add a little more bicarb than me to raise your TA slightly for two reasons. With your low TA at 50ppm you may find your pH falling rather than rising, only time will tell. When you carry out an calcium saturation index test you may find the water slightly aggressive (hence the recommendation to run the pH a bit higher as this has the biggest effect on aggressive water). Don't worry about old information that chlorine is less effective at higher pH, this has been disproved so keeping the correct free chlorine level relative to your CYA is the most important factor for correctly sanitised water.
Phew, hope that helped, look at Dennis's link to the pool calculator for help on details but dont forget that is written with some standard out of date information lime TA levels higher than really required.