Continuous Muriatic Acid Addition to Control pH

[mkubiniec]

My new saltwater pool has not been in service for almost 2 years. From the beginning, I have to add muriatic acid to control the pH. Right now, I am addition 1/2 to 1 gallon per week. Can someone please tell me why after nearly 2 years pH continues to creep up and I have to add acid every couple of days. I do not understand it. Is something wrong with the plaster? Should this issue be raised if the pool construction company? Thank you.

 

[Texas Splash]

Possible causes include:
- Elevated TA; can you post a set of test results?
- SWG increases aeration which in-turn elevates pH
- Additional aeration (spa spillover, water feature, etc

pH rising doesn't mean something is wrong, but generally we can help slow it down if we know more about your pool.

 

[Richard320]

Have you tested your fill water? I know I have to add a quart of acid every time I add 2" of water to my pool due to high TA.

 

[mikemass]

Welcome to the life of a Salt Water Generator. My first few years I thought the same thing (This Plaster is STILL curing?) It's not. I am going on my 11th year and still battle rising pH. The SWG is the culprit. I have tested this many times over the years. When I turn off the chlorinator and manually chlorinate with bleach I have ZERO pH rise. Within 2 days of running the SWG I red line on the pH. I have lowered the TA on the advice of this forum to see if that helps. But as of now I am awaiting a new cell (mine exceeded it's life). It's been a week since my SWG has been off and pH has held 7.2. Long term solution.... Get an acid doser. I plan too.

 

[Jimrahbe]

Captain,

One issue may be where you are trying to keep your pH level. I take care of three SWG pools, and none of them need acid on a regular basis. They all run a pH of 7.7 or 7.8. When I tried to keep the pH at 7.2, or so, I too had to add acid all the time.

Jim R.

 

[mikemass]

Hey Jim. Not sure if your post was in response to me or the OP. But I am not trying to maintain 7.2. It is there right now because last Friday I started the process of getting my TA from 80 down to 60. I added MA to get to 7.2 pH, and that same day my SWG crapped out. Low and behold, no SWG, no rise in pH. (still at 7.2)... When my SWG is operating correctly I also maintain around 7.8 by manually dosing with acid. Anything lower than that is just too much of a battle. I've learned to live with it.

 

[Jimrahbe]

Mike,

My post was intended for the OP (Captain K's pool).. but might apply to anyone that is continually chasing the pH roller-coaster. I know little about all the things that might cause pH increases, but I do know that I do not have the issue with my three pools. They are all basically the same configuration.. All three have Pentair IC40 SWGs, with VS pumps running at about 1100 RPM most of the time, none of them have water features that are general on. I have not tested the TA of the city water. About the only thing I do know, is that if I lower the TA to 60 or so, and aerate to bring the pH back to 7.4 or so, that it takes about two or three months for the pH to increase above 7.8. And then of course I do it all over again. During this time my TA will continually increase from 60 to 110 or 120, but the pH seems to level out at 7.7 or 7.8.

Jim R.

 

[mikemass]

Jim - You are one of the lucky ones. I wonder why your TA increases that much. Either way, if it works, run with it. Sorry about assuming you were replying to me earlier. I didn't see the "Captain K" in OP's sig line. I was just going off the 7.2 mention which was by me. I am very curious to see how my pH reacts when my new cell arrives with the now lowered TA. Thanks for the input.

 

[RobbieH]

1 gallon per week is excessive for a 17,000 gallon pool. Where I am, 1 gallon per week for a 44,000 gallon pool is excessive. I am guessing your TA is VERY high. Can you please post a full set of test results?

 

[mkubiniec]

Thanks everyone for your input thus far. Here is my chemistry - just tested:
TC = 5.0
pH = 7.9
TA = 90
CH = 400
CYA = 75
NaCl = 4500

I added about 7 cups of muriatic acid which brought the pH down to 7.1 and TA down to 70.

Here is the drill: I've been lowering pH to about 7.3-7.4. Then it creeps up to 8.0 and higher. Then I add in acid usually in about 4 cup doses. Of course, this brings down the pH. Then a few days later, the pH comes back up, then add more acid. Of course, TA starts to come down so then I am adding baking soda too. Cycle repeats.

I am on a well and the water is very soft and fairly neutral, but I do not add water to the pool very often. It rains maybe once a week. I guess I should do a complete round of tests on my well water just to see. But again, I rarely add water from my well so that is probably not the cause of pH constantly going up.

Under the post from "mikemass," he mentions about a lower TA recommendation from TFP. Could someone pass that on? Also, what is an acid doser?

If anyone else has any other thoughts, please pass. In the meantime, I turned off the SWG and will see what happens

Thank you!

Captain K

 

[tim5055]

Under the post from "mikemass," he mentions about a lower TA recommendation from TFP. Could someone pass that on? Also, what is an acid doser?

We generally recommend much lower TA than most pool stores for those who find that they are on the pH roller coaster like you are. For me, my pH is happier if my TA is around 50. Much higher than 50 and my pH starts rising fast. You may find that if you keep the TA a little lower and the pH a little higher (shoot to bring it to 7.6 instead of 7.2) your need to add acid may slow considerably.

When someone speaks of an "acid doser" they are generally talking about an automated system which adds the muratic acid automatically. The more sophisticated ones attempt to monitor the pool water pH and add what it thinks the pool needs. The low tech ones are nothing more than a pump that adds acid on a regular basis. Many of us use this same type of pump to add liquid chlorine. I use a Stenner Pump for my chlorine additions, but a Stenner will pump acid also.

 

[Jimrahbe]

Captain,

I agree with Tim, you should be trying to get your TA down below 60 and then Aerate to bring the pH up rather than allowing pH to come up along with the TA. From your description it sounds like you are not aerating at all. Is this correct?

I find this process is not a once and done thing. You need a good couple of free days. Add acid and bring pH down to 7.0 measure TA, and start to aerate.. Monitor your pH every couple of hours and when it get back up to 7.3 or 7.4 add acid again driving it down to 7.0 again. You need to do this over an over until the TA gets just below 60 (or whatever your goal is) and then keep aerating until the pH gets up to 7.5. Then you are done.

I believe that without aeration you are just feeding the roller-coaster affect.

Jim R.

 

[Jaimslaw]

I spent years chasing down ph creep. Even with lowering TA, my dual spillover spa + swg still gave rise to a vexing ph management problem. But after installing an acid dispenser, the benefit I achieved was far more than just the convenience of having the acid injected for me automatically. I was actually having to use a lot less acid to manage the ph creep.

I have come to believe that by auto dispensing the acid, one has far less issues with ph creep simply because the acid is being added slowly throughout the pump/filtering cycle. It appears that one is able to tame the ph creep while also pulling back on the amount of acid to achieve this simply by virtue of the acid being added in such small increments over the time frame of one's filtering cycle (5 hrs being my run time). Arguably, the classic manner of testing ph after a couple of days, then adding 8 to 12 ounces all at one time to get the ph back down is itself, a much bigger part of the ph creep problem than most realize (ie, aeration and TA not the only factors involved in this ph dynamic)

Anyways, there seems to be a logical nexus between the manner by which acid is dispensed into the pool and the degree of ph fluctuation, (tho far be it from me to provide an explanation for this in more scientific or chemistry based terms).

 

[mkubiniec]

Jim R

A point of clarification... I do not have an issue with rising TA. The reason my TA was so high (90) was because I added too much baking soda the other day after I added acid to bring down the pH.

So, assimilating the advice here (short of adding an acid doser)... it looks like I should bring TA down to about 50 and live with pH 7.6 or so. I'll see if that lessens the amount of acid I need to add. Once I settle out here, then I will experiment to see the effect of the SWG.

Forgot to mention, I do not usually aerate, i.e. run the waterfall or bubbler.

Thanks everyone.

 

[glider304guider]

I am in NC as well. I also have had to continually battle the high PH ever since I installed our SWG. I have adopted a dual method of chlorination to help try and keep the PH rise manageable. I keep my SWG set to a fairly low level of output and supplement chlorine with 3inch pucks in a floater. The acidity of the pucks help keep the PH in check. I still have to add acid but not as much as I would have to running the SWG exclusively. We get so much rain here that I am always dumping water out of the pool so my CYA never gets too high. I would love to just use the SWG exclusively but I don't like dealing with the acid too much. Like they say, every pool is a little different, but I have found this method keeps our pool fairly balanced.

Cheers