Can You Fill A Salt Water Pool With Softened Water?

Can You Fill A Salt Water Pool With Softened Water?

A salt water pool is typically filled for the first time either by trucking in water – which is the more expensive but quicker way – or by filling it from your garden hose which clearly takes much more time but is also cheaper. Moving forward, it’s a matter of topping up your pool with your outside tap as needed although rainfall and snow in the winter can help in that regard too.

But some pool owners wonder if they should use softened water from their water softener to fill their pool and if that might help produce better pool water quicker? After all, softened water has salt in it and a salt water pool needs salt. An interesting question to think about but there is a straight forward answer.

It’s more efficient to fill an empty pool with distilled water from a truck service and then balance the water afterwards than filling a pool with softened water. A salt water pool requires hardness between 200 ppm – 400 ppm but a water softener isn’t capable of producing enough softened water to fill a swimming pool anyways.

Low water hardness can lead to metal damage whereas high water hardness causes deposits on metal and irritates skin so a balance is required.

Let’s take a closer look at balancing total water hardness in a salt water pool and its implications on your pool and swimming experience.

Filling your salt water pool with softened water

Your pool water needs some hardness typically falling between 200 ppm – 400 ppm so a careful balance is required. Water is said to be hard when it has a high level of dissolved minerals such and calcium and magnesium in it. Many local water supplies naturally provide your home with hard water especially if you live in an area rich in certain minerals such as these two that enter the water system.

When you fill your salt water pool for the first time, your best bet is to pay a little bit more and have water trucked in as the filling will probably take 45 minutes to empty a 4,000 – 6,000 gallon truck. Total delivery time will depend how large your pool is but it will certainly take less than using your garden hose. Trucked in water is generally artesian spring water or distilled water so it is very pure and free of contaminants.

As far as cost, expect to pay $0.10 per gallon for 4000 gallons or $.09 per gallon for 6200 gallons or more. An 18,000 gallon pool would thus cost around $1,620 to fill completely. Depending on your local water costs, filling this same pool with tap water will probably cost around $54 assuming a 3 cents per 10 gallon charge for water.

Filling an empty pool with your garden hose could take 12 – 24 hours longer or longer and in your local area you might not even be allowed to do this given the amount of water you require. Plus you won’t get as pure water as you will with a quality water truck delivery. There may be overage charges too if you happen to live in an area that charges extra when you exceed a certain amount of water usage in a billing period.

What is hard water and what makes it a problem?

As mentioned, hard water occurs naturally and can be more prevalent in some jurisdictions that others due to the local terrain. Hard water typically means your flowing water into the home has a high level of calcium and magnesium and possibly other minerals.

Hard water can also be caused by high levels of aluminum, barium, strontium, iron, zinc, and manganese that also occurs naturally although sometimes old pipes can leech metals into your home water supply too. Using a water softener neutralizes these minerals which makes the water easier on your skin and clothing but also softer on your water-using appliances.

Adding softened water to your pool would likely result in water with low hardness which means you’d have to raise the hardness with calcium chloride. Using soft water simply isn’t practical either as a home water softener isn’t capable of producing enough water to fill a large swimming pool.

Your best bet is to fill your pool for the first time with water trucked in by a water service because while more expensive than tap water, is also quicker and more efficient. Truck water is generally distilled too so impurities have already been removed. Then over time as you need to top up your pool, you can use your tap for convenience.

Total water hardness in a salt water pool

Hard water refers to water that is delivered to your home with a high level of dissolved minerals such as calcium and magnesium. Many jurisdictions are known for having hard water and home owners are often well-served to install a water softener.

A water softener gets connected to your water supply in the basement and runs water through a salt brine which has the effect of removing the hardness by extracting out the calcium and magnesium before the water flows through your faucets.

The result is a softer water that is easier on skin and clothes and also tends not to result in calcium deposits appearing on faucets as with hard water.

With your salt water pool, you use salt to produce chlorine for the purpose of sanitizing the pool but the result also produces a softer water that is also easier on the skin and the eyes for that matter, especially when compared to regularly chlorinated pools.

Balancing water hardness in your salt water pool is an important aspect of overall water chemistry.

What happens if your pool water is too soft?

While soft water will feel nice on your skin to swim in, it can do damage to the pool and equipment particularly concrete, plaster and metal due to the corrosive effect. Even if you have a vinyl pool, there is concrete underneath the liner and you likely have a metal ladder.

Raising a pool’s hardness involves adding a calcium hardness increaser product (calcium chloride) to the pool which you can buy from your pool company. Raising a pool’s hardness is generally easier than lowering it but speak with your pool company and get them to confirm your water hardness and other water levels by getting a water test done to ensure other water factors are balanced.

What happens if your pool water is too hard?

When pool water is excessively hard, scaling can occur similar to what you see on water faucets in your home. When water is excessively hard it can damage the insides of piping and water-using appliances and has a similar negative effect on your salt water pool and related equipment.

Lowering a pool’s hardness is more challenging than raising it because to lower a pool’s total hardness, you need to drain an amount of water out and replace it with softened water. This could be water that has been softened by your home water softener depending on the amount required or it could be from a trucked water supply since water delivered by truck is generally treated and distilled.

Your bet bet? Don’t guess and try to do it yourself. Instead, take a water sample straight to your pool company and get them to test it. Based on the results they should be able to advise you what to do, how much water to drain from your pool and your best choice to replace it. You don’t want to try to figure things out yourself and accidentally end up lowering your hardness and then having to raise it back up again.

Water softener salt vs pool salt

Water softener salt vs pool salt
Water softener salt vs pool salt: Is there a difference for your salt water pool?

Many pool companies will simply tell you to buy water softener salt pellets and use that in your pool. I’ve been doing that since I became a pool owner and I think I’ve only bought actual pool salt once.

What’s the difference between water softener vs pool salt and does it matter for your salt water pool?

Water Softener SaltPool Salt
SizeTypically sold in 40 lb bags.Typically sold in 40 lb bags.
Popular brandsMorton System Saver, SureSoft Water Softener Salt, K-Life Sodium Free Water Softener Crystals, Diamond Crystal Water Softener Salt.Morton Salt Professional’s Choice Pool Salt, Aquasalt-40 Swimming Pool and Spa Chlorine Generator, Clorox Pool & Spa High Purity Salt.
FormCompacted round or oblong white pellets with rounded edges. NOTE: Only use white pellets if you use water softener salt. Do not use clear crystal water softener salt that looks like road salt with pink and brown tinges to it. This salt may have manganese and iron which is not good for your pool.Similar to crushed salt like you’d use in your kitchen except that pool salt tends to be ground coarser than table salt.
PurityGood quality white pellet water softener salt is 99% + evaporated salt.A quality brand is 99% + sodium chloride.
Dissolving rateSlowly. It’s designed to work in a water softener which only requires salt to dissolve slowly over time. In your pool, pellets will dissolve over several hours with the pump running.Fast. Crystalized salt dissolves quickly once poured into the pool which is what it is designed to do.
Effect on waterA pile of salt pellets will typically sit on the bottom of the pool for hours or more before they are finally completely dissolved with the pump running. In the meantime it can make pool water at the bottom slightly cloudy near the salt pile but this dissipates over time.Pool salt will dissolve very quickly and will immediately begin circulating throughout the pool.
CostTypically up to half the price of pool salt.Typically up to double the price of water softener salt.
ConsiderationsRemember that water softener salts are designed for that purpose so some brands include resin cleaners and rust remover features which are specific to a water softener not a pool. If you pick a water softener salt, pick a regular one that is just that: water softener white pellet salt that is 99% + pure salt. Some pool salt brands are even more expensive than double the price of water softener salt so pick a brand that suits your budget.

Should I use water softener salt in my saltwater pool?

Unless your pool company suggests otherwise for a specific reason, certain brands of water softener salt are generally suitable in your salt water pool. Given that you only tend to put salt in your pool once or twice per pool season, it’s not a frequent event. While water softener pellets take several hours or more to fully dissolve and certainly do so slower than dissolved pool salt, they do dissolve in relatively short order when the pool pump is running.

As long as you don’t purchase rock salt or road salt, you should be fine because it’s still salt, just in a pellet form. Stick with pure white pellets and stay away from crystal salt that has a clear look with a bit of pink and brown color in it as this is not meant for pool usage at all.

Also avoid water softener salt with additives or names that include resin cleaners and rust remover as these are features meant for a water softener. You’ll pay more for these brands of salt for no good reason.

How often should I add salt to my pool?

You add salt to your pool only when required and that’s when your salt levels fall close to or below the required amount. A salt water pool requires a salt level to remain at around 3200 parts per million (ppm) but a range of 2700 ppm – 3400 ppm is generally considered acceptable. Your salt water chlorinator usually has live salt level monitoring unless you have a very old or entry level system.

Once your salt level begins to fall below 2700 your system may start blinking or otherwise warning you that salt is getting low and at some point, the chlorinator will stop producing chlorine. This is a safety mechanism because at lower salt levels, the system has to work much harder to produce chlorine.

Consult my salt water pool chemistry chart to figure out how much salt to add to your pool. If you’d prefer to be sure, take a water sample to your pool company to confirm. You probably won’t need to add salt to your pool more than twice per season: Once at opening and perhaps once midway through the season.

Remember: It’s always easier to bring your salt level up because you just add salt to your pool. Lowering your salt level is more work because it means draining some pool water and refilling it with fresh water.

Will baking soda soften pool water?

Baking soda isn’t necessarily known by salt water pool owners as being a positive aspect to maintaining pool water chemistry even though it’s a common ingredient in commercial pool products to raise the alkalinity. Baking soda also has benefits to help raise pH and clear up cloudy pool water.

This is why you can purchase pool products with sodium bicarbonate (baking soda) but at a higher price than regular baking soda. The pH of baking soda is 8.3 so it is very alkaline hence its ability to prevent corrosion in your pool while also making water clearer and softer.

You can purchase larger packages of baking soda than is typically found in your grocery store as it does have benefits to your salt water pool that you may not be aware of, in a natural way too.

From baking soda manufacturer Arm & Hammer: A general rule of thumb is to add 1.5 lbs. of baking soda per 10,000 gallons of pool water to raise your alkalinity by about 10 ppm.


While using soft water to fill a pool seem intuitive it’s actually impractical since a home water softener can’t meet the capacity to fill a large pool nor is it the best choice. Proper pool chemistry relies on your pool water having some hardness so filling a pool with soft water will undoubtedly throw this out of whack. Your best bet to fill an empty pool is to use a water service delivered by truck and balance the water accordingly.

Moving forward you can use your garden hose to top up the pool as required. You will also receive rain water and possibly snow in winter than will fill your pool too so you’re likely getting several sources of water regardless.

Click here to read detailed research on the effects of hard water on health and other concerns.

Familiarize yourself with the benefits of baking soda in your pool. It’s a natural and cheaper way to maintain a clean, balanced pool rather than using more expensive commercial products that are largely comprised of baking soda but at a higher price.

Carl Mueller

I bought a home with a salt water pool in 2006 and soon realized the benefits over traditional chlorinated pools. On this website I'll discuss all the tips and tricks I've learned over the years. I'll also help you troubleshoot various problems with pools in general and ones specific to salt water pools that I've experienced personally!

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