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Thread: HELP!!! Can Muriatic acid ruin plaster?

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    HELP!!! Can Muriatic acid ruin plaster?

    Is Muriatic acid bad for plaster?

    Is shock bad for plaster?

    So I had mustard algae, and my ph was high at an 8. So I was advised to over shock even though my chlorine level was already too high, and add enough muriatic acid to bring my pool to a 7.2. So I added a couple bags of shock and half a gallon of muriatic acid in the deep end. My pool is 10 ft deep and 1500 or 1500 gallons. I don't remember which, it's pretty big. I scrubbed the walls, vacuumed, and ran the pump. After 4 hours is was at a 7.6 so I added the rest. 4 hours later I tested again and it was 7.2. I ran the pump for 2 days for 24 hours before returning to 12 hours a day. After 7 days I saw no algae return so I was happy. But when I went to clean the pool there was still shock on the plaster. But the chlorine levels were low. I put some tablets in the floater because I am worried about the plaster.

    So is Shock or muriatic acid bad for plaster? Did I do damage?

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    susa's Avatar
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    Re: HELP!!! Can Muriatic acid ruin plaster?

    How about posting a complete set of test results as that will help to determine the best answer(s).

    Prolonged low pH can certainly be a concern but everything is balanced against the full test numbers.

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    Mod Squad tim5055's Avatar
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    Re: HELP!!! Can Muriatic acid ruin plaster?

    I use muratic acid a couple of times a week on my plaster pool as it is the recommended way to lower pH. Shock granules just sitting on the bottom can pit it, but at this point it is too late to worry about, it's done. Let's worry about how you care for your pool going forward. Being in Las Vegas I doubt you are closing your pool tomorrow - so you need to care for it.

    If you read around this site you will find that we do not follow the normal recommendations of pool stores or their maintenance philosophies. Tell a pool store employee how we recommend pool care and they will say we are crazy. But, this is not something that just started yesterday. Some have been taking care of their pools this way for close to 20 years.

    You are using shock and tabs to chlorinate your pool and they get you into a vicious cycle as both raise the CYA (some cal it stabilizer) level in your pool. The higher the CYA level the more chlorine you need to keep algae at bay.

    To follow the pool care methods taught here you need to arm yourself with the knowledge and tools necessary to care for your pool.

    The tools are not limited to the brushes, vacuum hoses and other stuff you use around the pool, but include the most important item - one of the recommended test kits. You can buy a kit at a pool store, but again the pool store kits generally won't cut it. To effectively practice the TFPC methods, the FAS/DPD chlorine test is essential. All these kits contain that test while very few other kits do. Think of it this way, do you see a doctor blindly prescribing drugs without seeing the patient or having tests run?

    The knowledge is condensed in the Pool School link at the top of every page. It is a great community here, but we do ask that you read and try to understand the information being taught. Questions are always welcome and folks will try to direct you and teach you the methods.

    I would say start with these in the pool school:
    ABCs of Water Chemistry
    Recommended Pool Chemicals
    How to Chlorinate Your Pool

    Here at TFP we are going to ask for photos so we can see the condition of the water and are going to ask for a full set of test results.

    You need to make the decision - follow the pool store system or follow our techniques and spend less time and money caring for your pool.

    So, welcome to TFP!!
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Welcome to the forum

    Please add you pools information to your signature as outlined here - - > http://www.troublefreepool.com/conte...etting-started

    Muriatic acid can damage plaster so you want to make sure you drizzle it into the pool in front of a return jet. You can also measure it out and add it to a bucket of water and then add it into the pool in front of a jet so it's diluted some.

    Same with shock. If it's just sitting on your pools surface it can do some damage but it's unlikely with the pump running and if you brushed a couple times it was still sitting there two days later. When you added the shock did you just dump it in at one spot or broadcast it over an area like you should ??

    What I would be concerned about is that using tablets is raising your CYA level in the pool with each tablet and that is going to cause you to need more chlorine to sanitize the water and kill algae.

    Tim above gave you a good reading list to go through to get a better understanding of what is happening and what you are doing adding "shock" and "chlorinating tablets" to your pool.

    A set of water test results would be helpful as would the pools info.
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    Re: HELP!!! Can Muriatic acid ruin plaster?

    I'm sorry this is all really confusing for me. All I know is that I test my pool weekly with one of those taylor kits that just test for chlorine and bromine and ph. And it always comes out fine. I wanted to be sure I was doing things right though, so after a month I got it tested at Leslie's Pool and Supply where they've also confirmed 3 times that all of my numbers are fine. The only thing that was a little high was the chlorine. I was out of town 4 days and it rained a lot and that is when my ph went to an 8. Which is why I added more muriatic acid. I added it slowly and in the deep end in front of a jet. Half a gallon at first. Then half a gallon 4 hours later after retesting. The ph never got too low. It was between 7.2 and 7.5. A week later I saw no algae. I tested the water and the conditions were still good, the ph was a little high like 7.8. That's when I noticed what I thought was shock. But since I brushed it again and tested it again and the chlorine was low, I now realize or believe it was plaster dust. So Instead of shock I just put some tablets in the floater. I will go and read that thing about shock and floaters. Any way I also added a tiny but, like a cup of muriatic acid in the deep end again. I tested the next day and chlorine and ph were just fine.


    I don't have all of the numbers. I just do these 3 and go to leslie for the 7 pt inspection thing. And everything has always been fine. My water clarity has always been perfect and sparkly. The algae has never been on the water. Just a little yellow stuff on the walls. Which I didn't ever see until I had some trees I got cut down.

    Anyway I'm not worried about the water right now since weekly testing at leslie's reveals my numbers are all fine and the water is clean. I'm just worried about my plaster for this second. Why was all that dust on the floor? Can that stuff weaken my walls? Or pit my walls?

    What happens if I do get pits on my walls? Will water leak?

    I know I don't have all the information you guys want yet, I will try to figure all of that out tomorrow.

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    If you have read around here much you have probably seen that not much credence is given to pool store testing. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing.

    To follow the pool care methods taught here you need to arm yourself with the knowledge and tools necessary to care for your pool.

    The knowledge is condensed in the Pool School link at the top of every page. It is a great community here, but we do ask that you read and try to understand the information being taught. Questions are always welcome and folks will try to direct you and teach you the methods.

    The primary tool is the most important item - one of the recommended test kits. You can buy a kit at a pool store, but again the pool store kits like your 3 way kit generally won't cut it. To effectively practice the TFPC methods, the FAS/DPD chlorine test is essential. All these kits contain that test while very few other kits do.

    Think of it this way, do you see a doctor blindly prescribing drugs without seeing the patient or having tests run?

    As you can see, here at TFP we are going to ask for photos so we can see the condition of the water and are going to ask for a full set of test results. If you decide you want to continue with weekly testing and relying on the pool store's advice there is probably not much folks here can do but give general generic advice.

    To quote Dave, Site Owner of TFP:
    Throughout TFP, you will read that we suggest certain levels that good science and practical experience has taught us fall within safe ranges.

    Further reading of posts here will draw you to the inescapable conclusion that these guidelines work.......in thousands and thousands of pools worldwide.

    You may or may not choose to use these methods and guidelines or you may use some and not others. Our goal is to teach you what has been proven time and time again and then let you use that information to your benefit.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Hi,

    I read all of those links you sent me. They were very helpful. Besides the stuff about the CYA being in tablets that lead to Algae, I pretty much knew the rest. Everyone I talked to that take care of their own pools, including 2 pool guys told me just to test weekly and do the tablets and muriatic acid. So that's what I've been doing. I only ask the question because There seem to be little divots or pits in the walls and on the floor. And I didn't know if it was from a bad plastering job or if it was me?

    I will get the numbers you ask for from the pool store tomorrow. I appreciate all the help. I love learning.

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Quote Originally Posted by new View Post
    I will get the numbers you ask for from the pool store tomorrow. I appreciate all the help. I love learning.
    The problem is that most pool store testing leaves a lot to be desired and generally folks are reticent to give advice using it. Going to the pool store is not your solution, ordering a test kit and taking control is.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Thank you for the information on the test kits. I wasn't adding chemicals blindly though. Leslie tested my water. Upon telling them I had algae and I had zero phosphate levels in my water. A "pool specialist" at least that's what his business card says, that works there told me what to add.

    I'd been doing the same thing for 2 months and never had any problems. Till Saturday night it just didn't look right. So that's why I asked if muriatic acid or shock is bad for pools. And what should I use instead. But everywhere I looked on this website and internet I found people to say it's just fine in the deep end, in front of a jet, slowly. So I thought maybe it was a bad plastering issue. The plaster is 4 months old.


    I will look into buying one of those kits though.

    - - - Updated - - -

    I will buy the recommended one then. Thank you!

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Quote Originally Posted by new View Post
    A "pool specialist" at least that's what his business card says, that works there told me what to add.
    That is the key to this website, we want you to learn what your pool needs and to add ONLY what it needs when it needs it, and nothing more.

    You need to ignore much of what the pool store has taught you. As an example phosphate levels are a non issue. It is a problem made up by the companies so they can sell you a $38 solution in a bottle. They will scare you that your phosphate levels are too high and it is algae food. If your free chlorine (FC) is at the correct level based on your CYA (stabilizer) level no matter how much phosphate you will not have algae.

    The pool store will tell you that you want to keep your FC in the 1 - 3 ppm range, no matter how much CYA you have in the water. That is just rubbish. If you don't raise the FC levels as the CY goes up you open yourself to algae growth. Heck, early this year I had to keep my FC in the 14 - 17 range due to the previous owner's continuous use of tabs and shock which drove the CYA through the roof.

    I'm not sure if the employees don't understand the chemistry, they don't care to learn or they understand but want to sell you solutions - in any case the advice given in most pool stores does little more than move money from you to them.

    I know that the information we are giving is like trying to drink from a fire hose after letting someone else test and make decisions regarding the pool. Take it slowly, read Pool School (several times) and read other peoples posts. In short order the light bulb will go off and it will all start to come together in your mind.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    As many have already pointed out there are more than a cpl ways to maintain a pool. Some ways are inherently better than others. Using Science as your friend is the smartest way to maintain a pool. There is no magic potion to make pool water perfectly balanced at all times. There is however a very simple regimen of testing and dosing.

    Step one is to get a little knowledge. (the old adage "knowledge is power" has never been more true). Read "Pool School" 2-3x.

    Order a TF100 test kit from tftestkits.net, then while you're waiting for that to be delivered, read pool school again.

    Once the complete test kit arrives, test everything it allows you to test. If you're not sure of your results, ask questions. (there's how to vids on each test avail online).

    Once you have a complete set of test results, post them. Many many ppl here are willing to help. I'll go ahead and throw out a warning. You pretty much have to choose who to trust. This forum of pool owners, or your local "pool professional". If you pick and choose advice from each you will just be stabbing yourself in the back.

    From my experiences I can guarantee you two things.
    1. If you follow the TFPC method and don't slack off, you will have the prettiest water in the neighborhood, without any algae blooms. People here have issues only after they neglect to test and dose at the frequency they should
    2. If you follow the pool store method, you will have algae blooms. They accept this as a normal occurance once you reach what they call "chlorine lock" or "you have old water". which are both bull poo. The actual cause is extremely high CYA, accompanied by FC too low for that CYA.
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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Ok so I was not able to order my own kit so I had the pool store do one for me just for now because somebody asked for the numbers. It reported that everything was good. Just like it always does, when I go there or use my simple Taylor test kit.

    FAC 4
    TAC 4
    CYA 60
    TA 90
    pH 7.6
    TDS 1000
    Pho 100

    I think somewhere there has been a confusion that my problem is Algae. I had mustard Algae on the wall. The pool has always been crystal clear. My question was do muriatic acid and shock ruin plaster? Because even though I've been treating it the same for the past 2 months, all of a sudden it looks as if the plaster is chipping, pitting, making grooves and divots, disintegrating. The pool was replastered 4 months ago. The person who plastered it did all the brushing and stuff for 2 weeks after and then continued to maintain it for 2 more months. Then my uncle who used to be a pool man told me that I could care for it. And I had no problems until last week when it looks like the plaster is crackling. I was wondering how this happened. I know you guys don't trust those pool people. But every week I had them test it They've always said I was doing great and keep it up. I basically just did the acid and tablets until this last time. I added phos free and shock instead of tablets.

    In other words, is this normal? Why is this happening if all of my numbers are always balanced?

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Are the problem areas in the plaster in the area where you added the acid? If not, then I doubt it has anything to do with the acid or other chemicals you added so long as the overall pool pH didn't get too low (and you say it didn't).
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    Re: HELP!!! Can Muriatic acid ruin plaster?

    No it's all over the bottom and the walls and even steps look "crackled." My Taylor test said it didn't get too low. But are you saying that adding too much acid it could have done this?

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Quote Originally Posted by susa View Post
    How about posting a complete set of test results as that will help to determine the best answer(s).

    Prolonged low pH can certainly be a concern but everything is balanced against the full test numbers.
    FAC 4
    TAC 4
    CYA 60
    TA 90
    pH 7.6
    TDS 1000
    Pho 100

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Is your CH high ??
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    Solar Blanket, Well Water, Borax Added, TF-100 tester. ? too cold
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    Re: HELP!!! Can Muriatic acid ruin plaster?

    I see you are still posting pool store numbers. Have you ordered a test kit so you can verify these numbers?
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    I did yesterday. But the ph and chlorine match my taylor kit. So I figured the rest would.

    - - - Updated - - -

    What is CH and how do I test it? If the CH is high what can happen?

    - - - Updated - - -

    I really appreciate the help. I just want to figure out how to stop the pool from crumbling or if I need to call the plaster guy who did the job.

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    Mod Squad tim5055's Avatar
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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Quote Originally Posted by new View Post
    I really appreciate the help. I just want to figure out how to stop the pool from crumbling or if I need to call the plaster guy who did the job.
    no matter what, I would call him and voice your concerns. If nothing else he may be able I tell you what he thinks is happening.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: HELP!!! Can Muriatic acid ruin plaster?

    Something no one has mentioned (If they did, I missed it) is you need to be testing and dosing more than once a week. A little of time each day will save you time and problems in the future.
    Once you get the hang of the methods used here, you realize how simple it is to take control of your pool! Good luck and I hope your plaster is okay!
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