Many plants are sturdy enough and don’t mind receiving water from the tap, as small traces of chemicals like chlorine can benefit them. However, some plants are sensitive to excessive amounts of such chemicals. Therefore, it is best to let water sit for some time before use.
You should let water sit for 24 hours before using it on sensitive plants, primarily if you use greywater or rainwater. The sitting time will help sediments and other potentially risky substances settle to the bottom of the container, reducing the risk of your plants absorbing them.
This article will discuss when it’s necessary to let water sit before use on plants. I will also share alternative ways to make water safer for your plants and the best type of water to use.
Do You Have To Let Water Sit Before Using It on Plants?
You don’t have to let water sit before using it on plants. Tap water and rainwater are essentially safe to use even without pre-treatment. However, in rare cases, they may contain contaminants and excessive salts that can harm your plants.
In general, you can readily use tap water and rainwater on plants, except for very few situations that may require you to take necessary precautions.
Here are some of the situations wherein you may need to let your water sit before use:
During Fertilization Season
Letting water sit is necessary whenever you use fertilizers on your plants. Fertilizers already contain nutrients similar to those found in tap water, such as calcium, chlorine, and magnesium.
Fertilizers are also predominantly salt. Gardeners living near coastal areas may find it risky to use rainwater on their indoor plants without pre-treatment.
Plants need only a small amount of these nutrients. Using tap water or rainwater during fertilization season may add more of these chemicals to the soil than your plants need and can result in stunted growth or other problems.
Plants Are Temperature-Sensitive
Letting tap water or rainwater sit for a while can help regulate their temperature and make them safe for your plants.
Cold water can cause shock on plants and possibly send them into winter mode. They will most likely enter dormancy if constantly exposed to cold water.
Both hot and cold water can inhibit essential chemical reactions in the soil, as they deactivate temperature-sensitive enzymes and microbes.
Ideally, you should feed your plants only tepid water (20 – 25 °C / 68 – 77 °F). So if you could keep your tap water within this temperature range or harvest rainwater from spring to early fall, you wouldn’t have to let them sit for temperature regulation.
Potted and Indoor Plants
Outdoor plants are sturdy and can readily enjoy rainwater and water from the garden hose. In contrast, potted plants are more susceptible to fertilizer burn due to the limited growing space, while indoor plants are kept inside homes because they are sensitive to the elements.
Most plants require soil with good drainage, as it can drain excess water and leach harmful substances. However, it may not be enough to protect your potted and indoor plants from pathogens or toxic chemicals from some water sources.
The limited space in the pot and the small amount of water they receive cannot keep contaminants beyond the reach of the roots.
Why Do People Let Water Sit Before Using It on Plants?
Many avid gardeners pay extra attention to their plants’ needs to ensure they get the best out of them. Taking care of plants can sometimes be tedious, and not all people have plenty of time or resources to meet all their gardening responsibilities.
However, suppose you don’t have access to distilled water or find it too costly for your everyday gardening needs. In that case, it helps to pay extra attention and effort when using water with impurities. After all, water is one of the essential requirements for plant growth.
Some people let water sit before using it on plants to let harmful substances settle to the bottom of the container. Tap water and greywater may contain pathogens or toxic chemicals, which can harm plants in excess. Meanwhile, rainwater may contain salts that can also damage your plants.
There are plenty of accessible and environment-friendly sources available to water your plants. Some people even use treated wastewater or dishwater. However, some water types can pose serious risks for your plants if administered incorrectly.
Tap water may require extra precautions before it becomes safe for your plant’s needs. However, it’s not always necessary. In contrast, your plants can benefit from letting other water sources like wastewater sit for at least 24 hours before use.
Let’s look at the components of different types of water and the benefits of letting them sit before using them on plants:
Tap water in the US is generally safe for drinking because the Environmental Protection Agency regulates it. Most tap water in the country comes from public water systems that help ensure the water is safe for consumption.
While it is not rare for tap water to contain contaminants, most of them are harmless. Some may pose some risks to both humans and plants only when the levels are too high. Here are some common contaminants found in tap water:
- Microbes like bacteria, viruses, or fungi.
- Radionuclides like radon and uranium.
- Chemicals from fertilizer runoff or improperly disposed cleaning solutions.
- Biological pollutants like organic matter and sediments.
It is important to remember that not all tap water sources contain these contaminants. And even if they did, the levels will significantly differ depending on the environmental conditions at individual community water systems that supply water to homes.
Homes with private wells typically employ their own water purification systems to ensure safe and potable water access.
If you are worried about mechanical or chemical troubles that could compromise tap water quality, it won’t hurt to take extra measures to keep it safe. Sometimes, it can be as simple as letting your tap water sit overnight.
Here’s what you can do if you need extra precaution before using tap water on your plants:
- Collect tap water and store it in a container with a lid.
- Let it stand for at least six hours while keeping it away from direct sunlight, especially when using a plastic container.
- When it’s time to water your plants, use only the top ½ or ⅔ of the container.
- Be careful not to shake the water in the container to prevent spreading the potential contaminants.
Rainwater is an eco-friendly and economical alternative to tap water for your plant’s regular watering needs. However, it is not steadily available whenever you need it. As such, some home gardeners collect and store rainwater.
However, collecting rainwater may contaminate it, making it unsafe for your plants. For instance, storing it in a metallic container can result in rust. On the other hand, algal growth may occur in a plastic container.
Also, depending on your region, rainwater may contain salts, which can accumulate on your soil and affect your plant’s ability to absorb water.
Luckily, there are several ways to reduce the potential risks of using stored rainwater for your plants. Here are some of them:
- Boiling. It can help eliminate harmful microorganisms since most cannot survive high temperatures (100 °C / 212 °F).
- Physical water treatment. The process requires letting the rainwater pass through several conduit systems with various-sized rocks or pebbles. It can help remove some harmful elements, chemicals, and microbes.
- Chlorination. Adding chlorine to rainwater can remove many harmful microorganisms. However, it can pose a new threat to plants because many are vulnerable to high chlorine levels.
If you don’t have the means or the time to do any of the steps above, letting your collected rainwater stand for 24 hours is an effective way to prevent contaminants from getting to your plants. Be sure to store rainwater in a sterile container if you keep it for extended use.
Regardless of the source, wastewater needs a longer sitting time than tap water or rainwater. This waiting period is necessary because the wastewater contains more contaminants and harsh chemicals than other water sources.
Sometimes, letting wastewater stand for over 24 hours may not be enough to isolate the contaminants that can harm your plants. This fact is especially true when using soapy water from the dishwasher or laundry machine.
Often called greywater, soapy water contains contaminants that can compromise your plants’ health. Using this water source on edible plants like fruits and leafy vegetables can also negatively affect your health.
Using a water treatment method like filtration before using wastewater on your plants is best. You can let the treated water stand for 24 hours for extra precaution.
Here’s a video showing how you can make a DIY wastewater filtration system:
What Is the Best Type of Water To Use on Plants?
Distilled or purified water is the best type of water to use on plants. This type of water undergoes an extensive boiling and condensation process that separates the water from all contaminants, resulting in pure water. Its purpose is to hydrate your plants without the risk of causing diseases.
However, it may be too expensive to use distilled water if you have a large garden. That’s why many people try to find alternative water sources that are economical and eco-friendly.
Nonetheless, it is best not to compromise your plant’s health by using risky alternative water sources, especially if it’s your first time doing so. You should also be more cautious if you are growing edible plants.
Since you’ll also need safe and potable drinking water for personal consumption, it helps invest in a high-quality home water distiller or purifier. That way, you can get a steady and secure supply of clean drinking water for your family and your garden.
Water is one of the most vital requirements for plant growth and survival. Often, plants wither or die due to watering mistakes, such as applying the wrong amount of water or using contaminated water.
If you can’t use distilled water on your plants, you can choose from plenty of water sources available in your area. Tap and rainwater are generally safe to use even without pre-treatment for outdoor plants during warm seasons.
However, you may want to let them sit for a while before use on indoor and potted plants during fertilization season.
You can read my other article on how long you should tap water sit before watering plants here: How Long Should Tap Water Sit Before Watering Plants?