Hard Water, Soft Water, Rainwater: What’s Best for Your Garden?

There’s a good chance you have a water softener in your house—a device that pulls minerals out of your tap water, so you don’t get “water spots” on your windows or chalky buildup in your sinks and bathtubs.

Water softeners are easy to maintain and a great addition to your home. But how does softened water affect your garden? Would you be better off using hard water on your plants, so they benefit from all those extra minerals?

Here’s a comparison of hard water, soft water, and rainwater, how each one affects your garden, and what you can do to make sure your plants are getting the best water possible.

What Is Hard Water?

Hard water is water with high mineral content. It’s the result of rainwater that lands on the ground and flows through soil, pulling out minerals as it moves. By the time rainwater reaches an aquifer and gets funneled into a municipal water system, it’s usually high in calcium, magnesium, chalk, and lime.

High mineral content is good for drinking, but it dries out your skin, accumulates in your pipes, and leaves a chalky buildup on any surface it touches in your home. In many parts of the country, tap water is fairly hard. That’s why a lot of homeowners choose to soften their water.

What Is Softened Water?

Softened water is hard water that has been passed through a water softener to filter out minerals.

If you own a water softener, you likely refill it now and then with big bags of salt. That salt gets mixed into hard water, displacing and removing all the magnesium, calcium, chalk, and other minerals. You’re left with water that’s easy on your skin and won’t clog your appliances or cause unsightly mineral buildup in your sink.

The downside, however, is that softened water is harsh on your garden. The salt in softened water leaches in the soil when you irrigate. Plants don’t like salt, and over time, they can develop salt burn—yellow or brown edges on their leaves, thanks to salt buildup around their roots.

If you see white deposits on the surface of your garden and the edges of your plants’ leaves look yellow or burned, it’s a sign that softened water is depositing too much salt in your soil.

How to Prevent Softened Water from Damaging Your Plants

The good news is that there’s an easy way to stop softened water from damaging your garden. It is as simple as adjusting how your water softener is connected to your water lines. Instead of hooking up the water softener to both your hot and cold-water lines, only connect it to your hot water line. This way, when you irrigate with cold water, you won't cause salt buildup or salt burn in your garden, and you will still get the benefits of softened water in your home when you shower, clean, cook, and so on. 

Reinstalling your water softener may require an afternoon of work or a brief visit from a serviceman, but it’s an elegant solution for protecting your plants. 

What About Rainwater?

Ask most serious gardeners and they’ll tell you rainwater is the best option for irrigation. Rainwater is naturally soft, and it pulls excess mineral deposits below the roofline as it travels through the ground, maintaining ideal soil balance.

If you want to put in the time and effort to collect rainwater, your garden will benefit. The simplest option is to set up rain barrels beneath your gutters. They’ll fill up every time it rains, and you can then cover them and connect them to a drip irrigation system that distributes fresh rainwater evenly across your garden.

You’ll want to check your local laws before setting up rain barrels. Rain collection is illegal in some counties.

And if you’re near a major city or factory, you may want to test your rain to make sure it’s not too acidic. All you’ll need is a cheap packet of pH strips, which you can buy from any home improvement store, and a glass of freshly collected rainwater. pH measures acidity on a scale of 0-14, with lower numbers indicating greater acidity.

Dip the pH strip in the water and check the reading. Clean rain has a pH of 5.0-5.5[*]. If rain in your area is contaminated, the pH will be closer to 4.5, and you’re better off avoiding rainwater irrigation. Stick to tap water instead.

Final Thoughts

The type of water you use to irrigate makes a big difference for your plants.

As a gardener, you may want to consider how you manage softened water in your yard. It’s okay in moderation but irrigating with softened water too often may cause salt buildup in your soil and damage your plants.

Standard tap water (or irrigation water, which is common in the Western U.S.) is a good option for your yard, and a common choice for gardeners.

Rainwater is an excellent choice for watering your yard if you want to put in the effort to collect it. You just have to make sure the rainwater in your area is clean. Pollution from nearby cities or factories can make it acidic. If that’s the case where you live, you’re better off sticking to standard tap water.

Whichever type of water you choose, we can help you deliver it to your plants with ease. Whether you use a hose faucet, in-ground sprinklers, or drip irrigation, we have everything you need to minimize water waste and make sure your plants get the water they need to thrive.

Sources: 

"For plants, rain has benefits that tap water simply can’t deliver" Article published by The Mercury News - Home and Garden - March 2nd, 2023

"Gardening with Soft Water and Hard Water" Culligan Water 2023

* “What is Acid Rain?” EPA – June 24, 2022