Saltwater pools tend to be easier to maintain than chlorine pools and that includes keeping water chemistry in check. Water chemistry simply refers to various measurements that we’ll discuss in detail below that you need to keep in line so that water is clean and sanitized for swimming. While chlorine level is the most commonly discussed measurement, there are others that we need to keep track of.
Important Salt Water Pool Chemistry Measurements
Below are the main factors of salt water pool chemistry. We’ll discuss these measurements and what can happen when they get out of whack. And in the table below this section, we’ll highlight the ideal range for each measurement and what needs to be done when each goes out of range.
Salt is converted to chlorine by the salt water chlorinator so it’s important to keep the salt levels in the correct range so your system can continue to produce chlorine and keep the pool sanitized. When salt gets too high, it can damage pool parts, metal, concrete and other materials. When salt levels go too low, the system can have difficulty producing chlorine leading to cloudy water or worse. Salt is a corrosive material and high salt levels can damage metal, concrete, and patio equipment in general.
Free chlorine is the amount of chlorine available at that time to sanitize the pool. Combined chlorine has already attached itself to contaminants and is thus considered to be combined. Total chlorine is therefore free chlorine + combined chlorine. In a clean pool, combined chlorine will be 0 which is ideal. Free chlorine is necessary to continually keep the pool sanitized. When chlorine is low, pool water becomes cloudy or worse. When chlorine is too high, it can irritate eyes and skin. Chlorine dies out with use and needs to be replaced so it’s a continuous process.
Cyanuric Acid (stabilizer)
Cyanuric acid (CYA) is like sunblock for chlorine which gets damaged and dies when exposed to the UV rays from the sun. In fact, within several hours the UV rays from hot sun can kill most chlorine in your pool so cyanuric acid is used – and is often added directly to commercial chlorine and shock products – to protect against this. CYA is often added directly to the water by salt water pool owners since the use of chemical chlorine and shock is minimal compared to chlorine pools.
Total Alkalinity (TA)
TA refers to the ability of water to resist changes in pH. Low alkalinity over time may damage pool equipment and the pool itself. High alkalinity can cause the water to cloud up.
I’ve never personally had a problem with water hardness in our salt water pool. It depends at least in part how hard the water is in your local area that gets added directly to the pool in the first place. Very low calcium hardness can damage the pool but a very high hardness can disrupt and clog your filter’s ability to perform. It tends to be something faced more often in chlorine pools.
pH measures the acidity and alkalinity of water. A very high pH can cause irritated eyes, cloudy water and poor chlorination. A very low pH can also irritate eyes and can also corrode pool equipment over time.
Total Dissolved Solids (TDS)
When chlorine kills contaminants in the pool, they dissolve and while many will get removed by the filter, many remain in the water. Inorganic salts and organic materials increase as more chemicals are added to the pool. While there is no “ideal” level of TDS – the lower the better – high levels of TDS can irritate eyes, cause corrode metal parts, allow algae growth and screw up readings of other chemicals in the pool. TDS can be removed from the pool by draining water and refilling it with fresh water and also by regularly backwashing or rinsing your filter to get rid of contaminants.
Ideal Salt Water Pool Chemistry
Here is a table highlighting the main salt water pool chemistry measurements you will soon become familiar with, the ideal range for each, and how to best raise or lower them as required.
|2,700 – 3,400 ppm
|Add salt to pool to raise salt level. Add water to pool to dilute salt level.
|1 – 3 ppm
|Turn up chlorinator % to raise chlorine level, run pump longer during the day or add Shock. Turn down chlorinator or reduce pump time to lower chlorine level.
|Cyanuric Acid (stabilizer)
|70 – 80 ppm (outdoor pool)
|Add stabilizer to increase. Chemical chlorine products often have stabilizer pre-added.
|Total Alkalinity (TA)
|60 – 80 ppm
|Add baking soda to raise TA. Add muriatic acid to lower TA.
|50 – 300 ppm
|Check with pool company for advice as generally it’s not a concern for vinyl liner pools.
|7.2 – 7.8
|You can raise or lower pH with Up and Down type products ie. pH Up, pH Down. Salt water pools tends to have a pH that drifts upwards more so than a regular chlorine pool. You can also raise pH with soda ash and baking soda.
|Total Dissolved Solids (TDS)
|TDS increases as chlorine is added and organics dissolve. Decrease TDS by draining water and adding fresh water and by rinsing/backwashing pool filter regularly.
Fun Fact: Baking soda (regular sodium bicarbonate) that you buy in the store has a natural pH of 8. You can use regular baking soda to raise both the pH and alkalinity in your salt water pool. Here’s a great page from Arm & Hammer that discusses how baking soda naturally helps salt water pools.
How Much Salt Do I Add To My Pool?
I typically add 2/3 of my salt for the season in the spring at pool opening and the remaining 1/3 of the salt in the mid summer. In total, I use about 27 – 35 lbs of salt each season (60 – 80 kg). I always use white salt pellets. Salt crystals are not recommended as they don’t dissolve as well. If you dump salt directly into the deep end of the pool with the pump running, it’ll dissolve within a day or so.
Here’s a great chart that tells you how many pounds of salt to add to your pool according to the current salt level and pool size in gallons.
The chart also affirms that a salt level of 3,200 ppm is ideal and that 3,400 ppm is ok at the high end which matches what my chlorinator manufacturer Hayward recommends too.
Filling A Saltwater Pool For The First Time
If you’re filling a saltwater pool for the first time or if you’re refilling your pool, you’re effectively starting over in terms of pool chemistry. The two main ways you can fill a pool are from your backyard garden hose or through a water delivery service. Costs will depend on how much your region or city charges for water and how much local water companies charge to deliver it:
With A Garden Hose
This is obviously time-consuming and may not be allowed in your local area. It may also simply be unreasonable given the amount of water you’ll be adding.
Pros: Cheaper than getting water trucked in. If you have a problem with your pool liner you will see it and can correct it as water flow into the pool is much slower and you’re working on your schedule. It also gives your pool liner if you have one a chance to slowly stretch out.
Cons: Time-consuming and slow. May take 1-2 days to complete. You have to keep an eye on the pool filling. Your local region might have rules against filling a pool with tap water and may have a surcharge for large amounts of water usage.
Cost: $80 – $200 depending on pool volume and local water rates. An 18,000 gallon pool may cost around $160.
Ordering A Water Delivery Truck
It’s going to be quicker but more expensive than using your hose. A typical water delivery truck can deliver between 3,000 – 9,000 gallons of water at one time depending on their service and how much you require so you might only need 2-3 trucks brought in.
Pros: Quicker than using a garden hose. One truck may take around 45 minutes to empty so a complete pool fill may be 2-3 hours total. You often don’t need to be home when water is delivered. Some delivery companies will deliver pre-chlorinated water that may reduce the chemicals you need to add.
Cons: More expensive. If you find a leak or problem with your pool, you may have to pay extra to have the water service come back after having the problem fixed.
Cost: I’ve found online rates for .10 per gallon for 4000 gallons or .09 per gallon for 6200 gallons or more. So an 18,000 gallon pool would cost $1,620 to fill.
- Proper water chemistry insures a clean, clear saltwater pool that is safe for swimming.
- Familiarizing yourself with the main water chemistry components and safe ranges for each as listed above will save you time and money in the long run.
- Improper water chemistry can damage pool equipment, increase chemical costs and the maintenance time required on your pool.
- Filling or refilling a saltwater pool is typically accomplished through use of a garden hose (cheaper but slower) or with a water delivery truck (quicker but more expensive).
- Check out my full page on Salt Water Pool Chemistry Charts to learn more about the key elements of balancing a salt water pool.