What’s the Deal with Total Dissolved Solids?

We’ve all been there. Most of the time, maintaining your own pool is an easy and rewarding process. It can even be a calming routine: skimming your water, brushing down your walls, checking for clogs, testing your chemicals and adding more. At a certain point, some even get comfortable enough with the process that it becomes a peaceful way to get out of the house. But there are other times when we find ourselves crouching near the pool’s edge with a water test strip in our hand, wondering why on earth our chlorine is depleted when we just added it yesterday. Other times, that water test strip might report perfect levels, but when we look down into our pool itself, we can’t see the floor—it’s a disgusting, cloudy, murky mess. So what is up?

When it comes to maintaining your pool, knowing one specific measurement might be the difference between frustration and fulfilment. It’s called total dissolved solids, abbreviated as TDS, and it’s often woefully overlooked. I’ll explain what total dissolved solids are, why they deserve your attention, how to check that you have the ideal levels, how it might affect the other chemicals in your water, how to troubleshoot whether or not TDS is to blame for your pool’s current problem, and finally, how to lower your TDS levels when you need. Get ready to get answers for those questions you never knew you had.

What Are Total Dissolved Solids? 

I’m not trying to call you out or anything, here. But if you’re looking for one source of total dissolved solids, you’re going to need a mirror—and actually, this applies all swimmers. Every time we enter a pool, we bring in a whole lot of contaminants. Maybe it’s the lotion or deodorant we put on in the morning. Maybe it’s perfume and makeup. But don’t think that you can just shower before and after a swim and you’re good to go—it can also include your sweat, body oils, or other bodily fluids. All of these contaminants are collectively referred to as total dissolved solids (TDS). And while they’re not exactly pretty to think about, they’re an inevitable part of swimming. 

But TDS goes further than the contaminants that swimmers unknowingly bring into the pool. This is also a tool for the long game. TDS is a measurement everything that has ever dissolved in your pool water—that includes the byproducts of every pool chemical you’ve ever added, every bit of dissolved dust, dirt, pollen, algae remains, all that microscopic muck that attached to debris that falls into your pool. No molecule is exempt. So you’d better believe that there’s no running away from TDS building up in your pool over time.

Before you assume a high TDS levels are what’s causing murky water, make sure your pool is getting the circulation it needs with a variable-speed pump.. Thankfully, the Blue Torrent 2 HP Variable-Speed Pump is ultra-powerful, comes with a warranty, is eligible for rebates, and pays itself off in under a year by energy saved. As customer Robert Tafoya says, “Pump works quietly, efficiently, and is easy to install.”

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Why Do You Need to Keep an Eye on TDS?

I know, I know. It’s not ideal to think about all the microscopic contaminants slowly culminating in your pool. And usually, your sanitizer can take on TDS, no problem. But if your TDS spikes significantly over time, eventually your sanitizer won’t mix with your water. And you probably already know that as a pool owner, you’re going to want to do everything in your power to make sure your sanitizer works. It’s an issue of safety for yourself and your pool: without effective sanitizer, swimmers in your pool won’t be alone—there will also be a ton of bacteria floating along, which might include the kind that can make you sick. Ick. A high TDS can also cause a less significant erosion to metal pipes, ladder, and lights in a pool, since the chemical makeup of your water will be altered to be more conductive. 

How Do You Check Your TDS?

Before we get into the nitty gritty, let’s make sure you know how to test your total dissolved solids level in the first place. You have a few options here. There is a TDS test strip on the market which works similarly to the water test strips you probably know and love. If you’re looking for an even more accurate device, you can also find a digital test meter that measures the conductivity of your pool water to detect those dissolved particles. In my opinion, either one works. Now, let’s talk about what those numbers mean.

What are the Ideal TDS Levels?

The exact numbers are up for debate, but you’ll know if your TDS levels are in the ballpark or if you’ve got a problem. Basically, there’s no such thing as a too low TDS level—especially since it accumulates organically. Thankfully, there’s no such thing as a bottle of TDS that you can add to your pool—that would be absurd. So the only concern when it comes to total dissolved solids is when there are simply too many in your water.

Some claim that a TDS level of 1500 parts per million (ppm) and above is too high, but others say that level is 5000 ppm. That’s a big difference, but here’s the trick: if your TDS levels are somewhere between 1500 and 5000 ppm, just take a good look at your pool. If it’s a murky mess, or your free chlorine levels are reading way too low, you know that it’s time to lower your TDS, stat.

Got a nifty salt chlorine generator to keep your chlorine levels at the lowest, safest, most consistent levels possible? You made a good call. If your water starts to feel oily and taste salty—because despite the name and the amount of salt in the water, it usually doesn’t taste like it—then it’s time to check that TDS level. Chances are it’s above 5000 ppm, and it’s going to need to get lowered quick. Unfortunately, salt water pool owners aren’t exempt from checking their pool’s chemical balance. If only.

If your TDS levels are through the roof and you need to start off from scratch, start off on a better foot with a better pump. In top shape with the ultra-powerful Black & Decker 3 HP Variable-Speed Pump. It includes a warranty, qualifies for utility rebates, and pays itself off in up to 80% energy costs saved in all stages of operation. Check out this user review to see it in action.

You’ve Tried Everything. Now Look at Your TDS 

Perplexed pool owners rejoice. This is where they finally get their answer to a consistent question saturating online pool forums and maintenance requests for pool experts. Even the most seasoned among us who have taken DIY pool maintenance in stride could, at one point, find themselves scratching their heads. The problem? A cloudy pool with low chlorine levels—no matter how much chlorine you add.

If you are having repeated issues with maintaining chlorine levels and clear water, chances are that you’ve tried it all. You’ve checked your pH levels and alkalinity. You’ve tested your cyanuric acid levels and confirmed that they’re low. You’ve got your calcium hardness down pat. And your filter is working overtime, to no avail. So what is going on? Once you’ve balanced your water and run your filter to zero results, it’s time to look into your TDS.

Why Does High TDS Affect Free Chlorine?

It’s generally accepted that once your TDS has climbed too high, your free chlorine is going to suffer. Free chlorine, by the way, is the amount of chlorine in your water that is actual available to do the job. Because of a build-up of chemicals, including chlorine’s noxious byproducts called chloramines, only a certain percentage of the chlorine you add to your pool will have the room to actually start neutralizing contaminants and bacteria. It’s known by pool experts everywhere that TDS is another one of those walls standing in the way—and if it gets too high, your free chlorine will be too low to be able to tell that it’s getting anything done at all. 

Everyone agrees that high TDS levels affect free chlorine. But the reason why this happens, believe it or not, is still up for debate. One theory is that a high TDS level indicates that all those solids that have dissolved in your water take up physical space on a molecular level, and keep your sanitizer from moving freely. Gives “free chlorine” a whole new depth, right? Another theory is that those total dissolved particles are bonding to the chlorine molecule and changing the way it interacts with the water itself—sort of like a hitchhiker who persuades a driver to turn the car around. Yet another theory is that high TDS doesn’t actually inhibit the way the sanitizer works at all. Instead, it interferes with the water testing results itself, producing low chlorine levels when the levels are just fine.

That last one I believe the least, since many of those with high TDS levels clearly do experience murky, cloudy water. In either case, it’s good to know there’s a little bit of mystery everywhere—even in the pool world. Keeps it interesting.

Is your above-ground pool experiencing murky water due to inefficient circulation? Try the Copper Force Above Ground Pool Pump, which has a start capacitor and different horsepower options. According to customer Doug Paar, “The pump is very quiet and has good pressure. I would recommend.”  

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Got a High TDS Reading? That Might Be a Problem

Alright, so what if you discover you have high TDS levels but your pool seems, well, completely fine? Do you still need to lower the water? Well, no. In fact, not at all. High TDS readings don’t always indicate a problem. In order to understand why, we need to look at the nature of TDS itself.

It’s important to keep in mind that TDS isn’t one thing—everyone has a different arsenal of chemicals they use to maintain chemical balance in their pool, and many pool owners use a different kind of sanitizer than simple chlorine. Even chlorine itself comes in a few different forms! Since TDS is a combination of everything that has ever dissolved in your pool, and different pools have a different makeup of matter dissolving in them, each pool owner’s TDS level is going to indicate its own specific makeup of constituent particles.

Instead of only considering your TDS reading, it’s also important to keep in mind what particles can be harmful in large numbers. Chlorides and sulfates are the most common culprits for reducing how effective your sanitizer is. Phosphate and nitrates are also pretty sketchy chemicals, since they both eat up chlorine and feed algae extra nutrients. That’s wrong on so many different levels.

So if your TDS level is a little high, there’s no reason to act immediately. Just keep an eye on your pool. If it starts to sprout algae or cloud up, and your chemical balance is right on the mark, you’ll know that your TDS is most likely the culprit.

TDS Levels are Fine, But Your Pool is Not?

Okay, so you came here sure that your TDS levels were off—but your test came back normal. That’s okay. There are so many other possibilities for why your pool is experiencing issues, and most of them are a lot easier to handle than lowering your total dissolved solids, anyway.

If you have cloudy, dull water, check your filtration, circulation, and the chemical balance of your water.

If your chlorine level drops off overnight, even after you use pool shock, make sure your cyanuric acid level is under 50 ppm.

If you have trouble with algae, yikes. Check that your phosphate level is less than 1000 ppm, and give that stuff a double or triple pool shock treatment. The fact of the matter is that sanitizer isn’t really a match for algae, anyway. A powerful, fast-acting pool shock is your best shot. 

If you’re experiencing a lot of pool scale, check that your calcium hardness level is under 400 ppm.

Check these out—it’s likely that TDS isn’t to blame this time around. But give it time, and your total dissolved solids levels will eventually spike. It happens to all of us.

Keep your sanitizer working at its highest capacity by switching to a powerful automatic cleaner that works on its own. Look no further than the Blue Torrent MyBot Inground Robotic Cleaner, which works powerfully to keep your walls and floor sparkling clean. As customer David Lain says, “Very pleased. My wife loves it.” Check out this user review to find out more.

Is Your TDS Signaling Something Else Out of Whack?

Even if your TDS levels are high, follow this checklist to make sure that it is the actual culprit for your murky water. Remember, high TDS is not always a bad thing—and there’s a chance there’s something else in your pool that’s out of whack.

1.     Filtration and Circulation

Has your filtration process changed over time? Is your pump’s horsepower no longer cutting it? Make sure that you’re running your pump for the right amount of time every day, and that your system doesn’t have any nasty clogs slowing it down.

2.     Get Back to Water Balance 

This one might seem like a no brainer, but I can’t even tell you how many pool owners overlook one of their chemicals and assume the issue must be TDS. Since lowering TDS is a lot harder than simply dropping more of a chemical into your water, you’re going to want to make sure your chemical balance is perfect before taking more extreme measures.

3.     Phosphate Problems

Again, phosphates (and nitrates) can consume your sanitizer and feed your algae. Ick! Use a test strip to test for phosphates, and use a phosphate remover to get those guys out of there.

There’s Only One Way to Lower Your TDS

Tried it all, and you know your high TDS is the problem? Well, you’re going to need to lower your levels for sure then. The reason I had you check every possibility is because unfortunately, there’s only one way to lower your TDS, and that’s dilution. Womp womp. This is never the answer I like to give. 

If you have an inground pool, you’ll need to give it a partial drain and refill it with fresh water—but make sure you don’t drain it too low, or that you’re equipped to prevent the dreaded pool pop up that sometimes occurs when inground pools are drained. No catastrophes here, please!

If you have an above-ground pool, you’ll also need to give it a partial drain and refill it up with fresh water. But chances are your TDS is lower, since above-ground pools tend to be emptied and refilled for the swim season.

No matter what pool type you have, make sure that you reset your chemical balance as soon as it’s filled back up. This is one of the reasons why draining is such a bummer—in a sense, you have to start again from scratch. But hey, you’re going to love how clean your pool is now that your TDS is back to normal, right? Let’s focus on that.

You’ve put the work into your pool. Now give yourself extra time to reap the rewards by extending your swim season. All you need for a longer, more comfortable swim is the perfect heat pump, like the Energy-Saving ComforTemp Pool Heat Pump 95,000 BTU to heat 18,000 Gallons. According to customer Steve, “Simple install and simple set up. Heated my pool from 66 to 82 degrees in about 2 complete days.”

Ta Da, Success!

This measurement might be often overlooked, but now you’re an expert. Congratulations. Next time your chlorine levels are reading persistently low, or your water chemistry reads perfectly but is clearly out of whack, you’ll know exactly where to look. So don’t worry about all that stuff you bring into the pool with you. Next time it builds up, it’ll be a breeze to handle. Now that’s one clean, clear pool—thanks to you. Enjoy.


This article explains how you can backwash your pool filter efficiently. Want to know how to clean the bottom of your pool? Read more here.

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