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High alkalinity causes major hot tub issues. But why is your alkalinity high? Let's start there and help lower the alkalinity in your hot tub.
Creators & Guests
What is Hot Tubs 101?
A podcast for hot tub owners covering hot tub maintenance and water chemistry.
Everyone. And welcome to hot tubs 101 by Swim University, where we help you keep your hot tub clean and clear all year. My name is Matt, and I'm the founder of swimuniversity dotcom. And on this episode, we're talking about how to lower alkalinity in a hot tub. Let's jump in.
Matt Giovanisci:Real quick. If you want more help taking care of your hot tub, be sure to grab our free hot tub cheat sheet at swimu.com /spasheet. So if the alkalinity in your hot tub or swim spa is high, it can cause cloudy water and reduce the effectiveness of your sanitizer. That means chlorine, bromine, etcetera. So to lower your alkalinity in your hot tub, add a pH Decreaser.
Matt Giovanisci:Yes. That's you heard me correctly. If you want to lower alkalinity, you add a pH Decreaser or what's called soda ash if you visit the laundry aisle of your general store or your hardware store. This active ingredient in both of these products is sodium bisulfate. Because there is no such chemical, believe it or not, called alkalinity decreaser.
Matt Giovanisci:That's just a fun fact. So, yes, pH Decreaser will lower alkalinity. But let's answer the question, why is your alkalinity high in the first place? And what even is alkalinity in your hot tub? Well, the difference between your water's pH and alkalinity, first, we have to understand that pH is the measurement of how acidic or basic your hot tub is.
Matt Giovanisci:Alright? So if you look at a scale, it goes from 0 to 14. Okay? Or 1 to 14, really, because it's 0 being battery acid. Number 1 being stomach acid, 3 or or even 2, as low as 2 pH.
Matt Giovanisci:And again, it's not measured in any sort of it's just numbers. 2 is white vinegar, 3 is orange juice, then 4 is a tomato, then 5 is black coffee, and even 4 is beer too. Tomatoes and beer kinda the same, acidity range, if you're into that kind of thing, which I am. And then water is around 7. So our tiers, human tiers, are about 7.
Matt Giovanisci:Okay? That's where we wanna keep the pH level balanced or at least close to that. Now, on the other side of the pH scale, which goes all the way up to 14, we're talking about drain cleaner, which is awful, then it goes down to bleach and soapy water and ammonia, and then it goes down to baking soda, which, you know, we use baking soda to increase alkalinity. So again, the goal is to keep our pH level balanced, but not exactly at 7. We want it at 7.4 to 7.6.
Matt Giovanisci:That's not too acidic. It's also not too basic. Now just for a basic understanding of pH, for all the decimal points actually matter here. Okay? So 7.0 is what our human tears are, roughly.
Matt Giovanisci:Okay? So when you cry, it usually doesn't burn. And the reason that it does burn, if you do cry, it's because you're wearing makeup or or something, you know, or a lotion that's getting in your eyes. But usually, it doesn't burn when you when you cry. Right?
Matt Giovanisci:So that means our tears are a neutral pH balance. But in a hot tub, we want it a little bit higher, 7.4 to 7.6. Now, when you go up a single decimal point, so if you go from 7.0 to 7.1 to 7.2 to 7.3, etcetera, That's 10 times higher each decimal point you go up. So it's it's a big jump. Okay?
Matt Giovanisci:So going from 7.4 to 7.6 is a 20 x increase. Okay? If you can think of it that way. Now alkalinity on the other hand is the capacity of water to resist acidification. Alright?
Matt Giovanisci:So we like to think of that as as alkalinity being pH's bodyguard. Because hot tub pH and pH on its own is volatile. And anything that interacts with your pH or or any or sorry. Anything that interacts with your water can drastically change your pH and cause extreme fluctuations. You could have a pH of perfect pH for your hot tub at 7.5, and you get in the water and you could drop it down to 6.8.
Matt Giovanisci:Alright? So a high now here's like, okay. Why is that such a problem though? Like, why is having a 6.8 a problem? Well, low pH causes corrosion.
Matt Giovanisci:Acidic water is corrosive. What about high pH? Well, that causes scaling in cloudy water because it makes it it's very basic, and it makes your skin very dry. And the opposite, low pH, makes your skin very acidic and itchy. It's it's bad both ways.
Matt Giovanisci:So you want it perfect. But when you have the right amount of alkalinity, this is gonna take the hit, the acid hit, before it affects your actual pH, reading. Alright. So without alkalinity, again, your ability to maintain pH would be all over the place. So alkalinity and pH are related and they help each other, but they are not the same.
Matt Giovanisci:So unlike pH, total alkalinity is measured in parts per million or PPM for short. Most resources out there on the Internet will tell you to keep it between 80 a 120 parts per million. However, we recommend keeping it a little bit higher at a 100 to a 150 parts per million to give yourself a little bit more room to play because it's, it's gonna be it's gonna take the acidification hit. So going from 150 down to 80, that's a much broader range than going from, say, 100 down to 80. Okay?
Matt Giovanisci:Now, what causes high alkalinity in a hot tub? Well, to be fair, high alkalinity is not a common issue in hot tubs. Mainly because hot tub owners, hopefully, if you're listening to Swim University or if you've read our stuff or if you watch our videos, you're draining and cleaning your hot tub every 3 to 4 months to keep things from building up in your hot tub, which could cause alkalinity. So some of those causes being, yes, too many chemicals. You could be adding too many chemicals to your hot tub, which can increase your total dissolved solids reading or your TDS reading for short.
Matt Giovanisci:But if you drain and clean your hot tub every 3 to 4 months, you really never have to worry about this. Also, high TDS or high total dissolved solids causes foaming. So it's a good thing to drain it and clean it every 3 to 4 months. Sweat, lotions, and other gross body stuff, you know, will actually, raise the pH. Okay?
Matt Giovanisci:And it could, you know, so you're talking about body lotions, sunblocks, perfumes, hair gel, shower gel, all those things. Some of those things can lower pH. Some of those things increase pH. And by increasing pH, you're also probably increasing alkalinity. Because again, they're related, but they're not the same.
Matt Giovanisci:Your water source, you might live in an area with a high high pH and a high high alkalinity reading. So if you're unsure, if you got a new hot tub, you can ask your township. You could probably go on your township's water, like municipal water supply website and actually get test results. You can actually see what the alkalinity is, or you can just pour a little in a cup and use your test strips to check the alkalinity. And then, of course, there's human error, which means you accidentally added too much alkalinity increaser or baking soda.
Matt Giovanisci:Whoops. So what happens if alkalinity is too high in a hot tub? Well, the main thing that can happen is it renders your sanitizer, like your chlorine or bromine, basically useless. Alright? Chlorine and bromine are much more effective when the pH level and the alkalinity level are right perfect, perfectly balanced.
Matt Giovanisci:That's why so important that we keep the water balanced. It's good for your skin, it's good for your soak, and it's good for your sanitizer, which keeps you safe when you're soaking. Now, if you have if if you have high alkalinity and your chlorine and bromine are not working well, well, this can cause green water and bacteria to grow, again, making your hot tub unsafe to soak in. And secondly, it can cause scale build up, which will make your hot tub work twice as hard to heat up because that scale lines the inside of your hot tub heater, and it just causes it to have to, like, heat through that to heat the water. So, and not a doctor, but all of this puts soakers at risk for skin issues like hot tub folliculitis, which you might heard as hot tub rash.
Matt Giovanisci:When your water's not sanitized, sometimes that can happen. It's pretty common actually. Plus, it puts you at risk for empty wallet syndrome, which is a, sometimes a problem for both pool hot tub owners and boat owners. So, how do you lower the alkalinity in the hot tub? Well, we mentioned earlier that the easiest way to lower alkalinity in your hot tub is by using a pH Decreaser with the active ingredient being sodium bisulfate.
Matt Giovanisci:So make sure that you look at your, if you buy pH Decreaser, which we do recommend, that every hot tub owner has pH increaser and pH decreaser on hand. They come in real small bottles, perfect size for hot tubs, And just make sure that whatever you're buying, the active ingredient is sodium bisulfate. Okay? Now before you add pH Decrease to your hot tub, you need to know how much water your hot tub holds. Okay?
Matt Giovanisci:So, we have a calculator on our website that will tell you. So you can go on our website swim university.com to find that out. You can also check check your manufacturer. They usually have it online, how many gallons of water or how many liters of water are in your hot tub. So the first thing you wanna do is test the water.
Matt Giovanisci:Now, we recommend using a test strip. Although it's not as accurate, I get a lot of crap for that. Yes. Yes, pool guys and hot tub guys and hot tub nerds out there, hot tub test strips are not as accurate as a liquid test kit. However, they are way easier, and we're not trying to get super accurate here.
Matt Giovanisci:We just need to be in the ballpark. Okay? So that's what I like to use to test my hot tub water is a is a test strip. Ideally, you would take the test strip or you would take a sample of water out of your hot tub, generally from the middle of your hot tub using a a plastic bottle, a clean plastic bottle or a glass piece, you know, just a drinking glass that's also clean, not doesn't have any soap or residue in it. Make sure you rinse it.
Matt Giovanisci:And then let it sit at room till it comes to room temperature and then test it. It'll it'll be a little bit more accurate if you do it that way, even for a liquid test kit. Then you're gonna add pH Decreaser, again, sodium bisulfate. So for example, if your hot tub has a 1,000 gallons of water, which is pretty big, that's, like, twice the size of a normal hot tub, you would use about 3 ounces or 85 grams to lower the alkalinity by 10 parts per million. And you wanna sprinkle or what we call broadcast this powder around the surface of your hot tub while it's running to keep it to help it mix in.
Matt Giovanisci:Then number 3, you just wanna retest the water. So after 24 hours, test the water again and readjust if you need it. Now if you go on our website, if you go to this, article, you will see that we actually have, a chart on how to lower the alkalinity with pH Decreasers. So if your test strip reading is say 8, a pH reading of 8, you would add 1 teaspoon, for example, for 300 gallons and that should bring you right down to the the right alkalinity and the right pH. Alright?
Matt Giovanisci:And of course, yes, if you, if you add pH decrease, it's also gonna decrease the pH. I should have mentioned that. So again, like, yeah, what should be adjusted first, alkalinity or pH? Well, alkalinity, will alkalinity increase or will always increase pH? Alright?
Matt Giovanisci:Now alkalinity decreaser will well, so alkalinity increaser, if you add it, will increase your alkalinity, but it will also increase pH. And if both readings are low, you start with increasing the alkalinity first and you test the water again. And if your pH is still low but the alkalinity is good, then you just add a pH increaser or soda ash or sodium carbonate. Now, it depends on what your current readings are, so it's important to always test your hot tub water before adding any chemicals to make adjustments. K?
Matt Giovanisci:Here's the other thing. I get this question a lot. Does vinegar, specifically white vinegar, lower alkaline in a hot tub? No. White vinegar or any other type of vinegar does not lower alkalinity.
Matt Giovanisci:It will lower the pH in your hot tub, but I would not use that because it's gonna have other things in it. It's not gonna be pure sodium bisulfate, which is just gonna decrease, alkalinity and pH. Usually, vinegar has other things. And if you use the wrong vinegar, like apple cider or red wine or rice or white wine. It's just gonna cause problems.
Matt Giovanisci:You're actually gonna add sugar to the water, and that's gonna cause foam. Finally, here's some tips on how to control alkalinity. After adding any chemical to your hot tub, allow your water to circulate for at least 5 to 15 minutes before retesting. Better yet, it's better to just retest it the next day, 24 hours. That would be great.
Matt Giovanisci:You can keep your alkalinity between 80 and a 120 parts per million, but again, we recommend a 100 to a 150 parts per million to give your alkalinity more room to come down before having to adjust it again. And for the most accurate water test, you wanna collect a water sample into a clean cup and test it after it is cooled to room temperature. And use a test strip because a test strip is gonna be fast and accurate, but or sorry, fast and close, but a liquid test kit is going to be more accurate. So if that's something you're, you wanna you wanna get into, certainly, you can use a liquid test kit. It just takes a little bit longer to do.
Matt Giovanisci:But again, more accurate. Both of these, by the way, both test strips and, liquid test kits require you to see color and to see color accurately. So if you're color blind, it you might have a trouble seeing it and comparing it to what you need to compare it to. But if you get a liquid or a test strip, they do make digital readers. So you can, you know, use a computer to read it for you.
Matt Giovanisci:You also never wanna mix any chemicals together, so add them 1 at a time and at least 5 to 15 minutes apart with the cover off. And another thing you can do is add aeration to the water. So using your air jets or a built in fountain, that will help control the pH without affecting the alkalinity reading. So adding air, what that does is it increases oxygen and decreases carbon dioxide, which raises pH without raising alkalinity. And then finally, you just wanna change your spa water every 3 to 4 months.
Matt Giovanisci:And remember, if you need more help with hot tub maintenance, be sure to grab our free hot tub cheatsheet at at swimu.com/spa sheet. And if you found this episode helpful, subscribe for more hot tub maintenance tips on your favorite podcasting app. And when you do, please leave us a review because your support will help more hot tub owners just like you find this show. That's it. Thanks again, and happy soaking.