Is it better to water your plants with rain water collected in water butts? I mean is that better than water straight from the tap?

And is it just a matter of temperature (presumably plants don't like to be soaked with very cold water (as mains tap water is)? Or are there other factors?

I'm interested in the effects on plants, rather than the separate issue of the cost to the planet of using mains tap water.

See also Does water temperature affect plant growth?.

  • 1
    Apart from the chemical differences, I'd say rain water is a much better choice in drier parts of the world, given the scarcity of water there. Mains water typically comes from river systems which can't always bear the over-extraction of flows and the whole ecosystem suffers. Rain water on the other hand is simply being flowed past your plants' roots prior to resuming its former natural subterranean course (esp. if it was going to flow into the storm water system instead), so it barely impacts the local ecosystem at all.
    – Lisa
    Commented Dec 12, 2011 at 23:44
  • Email your city and get the mineral levels of each mineral they test for in your water. For instance, if it's high in calcium, that could be good or bad depending on what you're growing and what your soil is like (acidity, mineral levels, nutrients, etc.) Commented Jan 10, 2015 at 6:13
  • This is a question that can and should be addressed with science-based answers, but currently none of the answers have any citations into the primary or secondary literature.
    – Reid
    Commented Jan 12, 2020 at 21:35

9 Answers 9


Your tap water will have particular properties depending on where you live, the source of your water, and whether you have some sort of water softener or filtering system. My tap water, for example, is from the public system and is considered 'hard' because it has a high mineral (calcium and/or magnesium) content. If I use tap water consistently on certain plants, I can see white rings of calcium deposits sitting on the soil surface; this can change the chemical properties - such as the pH - of the soil which can affect plant growth. Softened water has higher levels of salt than plants prefer, and these salts can build up in the soil. I've never seen the chlorine in public water causing any ill effects on my plants, but if you have sensitive house-plants you can let chlorine-treated water sit out for 24 hours to let the chlorine evaporate. As long as you live in an area that isn't subject to extremely acidic rain, rainwater is preferable because it's missing things like excessive minerals or disinfectant chemicals.


If your plant is not special plant such as carnivorous plant, any water from the tap is okay.

The fact is tap water may contain different things such as chlorine, and a lot of different minerals. My plant is drinking water with chlorine day to day, but they are thriving.

In the end, rain water maybe good, but who knows what is inside the water because the contamination from human activities such as car driving and industrial plant releasing exhaust fume from the chimney. Check this link, and this too. You may want to have your own judgement.

I think rain water and tap water are both okay in some extent, on the other hand, distilled water is not really that good because most of the minerals are lost. I prefer tap water ,it is cleaner because chlorine kills bacteria.


Rain water is always the better choice. City water can contain elements that could eventually harm the plant. When the rainwater is unavailable the tap water will be just fine.

  • 3
    "In most cases". The additional elements are generally not a problem (look how many of us are forced to water the garden with tap water), but some plants can be very sensitive to it. Carnivorous plants should always be watered with rain water or deionised/distilled water. Many orchids will be the same.
    – winwaed
    Commented Jun 18, 2011 at 13:51
  • 2
    Just beware of rooftop contamination, if that's how you're collecting the rainwater.
    – bstpierre
    Commented Jun 18, 2011 at 15:31

Sweet peas, garden peas and broad beans prefer rain water. Although they still grow when watered with tap water the results you get from watering with rain water are vastly improved. Chlorine and other substances in mains water inhibit the uptake of nutrients and thus reduce plant growth and health.


Rain water has a neutral pH. It's usually softer than tap water and soaks in the ground deeper than a hose watering; people don't water long enough to equal the soak of a good rain. There are particles picked up in the atmosphere during a rain which offer nutrients to the soil that tap water does not have.


I can understand what many are saying here, but to me rain water is best. I live in the country and no matter how much water I give my plants they won't grow as much as they grow after a rain soak. My best guess is that plants may like electrolytes or charged particles more so than we understand. I have seen plants that have not grown for a few years of tap water, grow two or three fold after a good soak of rain water.


If you are growing from seeds I would definitely use tap water. This is clean water and free of any microbes, bugs etc., that may cause damping off or rotting etc. Rain water from water butts would be fine on most outdoor plants. Rainwater is also as others have said is generally softer than hard processed tap water, so things like orchids or acid loving/lime hating plants would prefer rain water.


Rainwater is generally better. Chlorine, fluoride, bleach and such, which are in a lot of city water, may not harm your plants in the drinkable amounts, per se, but they certainly may harm the beneficial microbes in your soil, which will reduce the benefit you would gain from those microbes (which may be considerable). I find that my tomato plants last year preferred filtered water to regular city tap water, probably for this reason. They required less water and grew better when I filtered the water. I imagine rainwater is similar to filtered water.

Rainwater is probably pretty much devoid of minerals. It may contain chemicals via pollution, however, and your guess is as good as mine as to what those chemicals will do to your plants and soil microbes.

Well water, without chemicals added, has the potential to be better than rainwater, depending on your soil and the composition of the well water, because your soil may need those minerals. On the other hand, the minerals in the water may have come from the above soil in the first place, in part.


Water from a hose is usually delivered at a faster rate than rain falling on say pottered plants. Usually all the rain falling on a potted plant remains in the pot but the outflow at the bottom of the pots with hose water will take many leached nutrients with it. Another factor is the build up of hard deposits on the parts of the plant which take in the water when tap water is used. Note this similar effect also happens when a car is "washed" with rain how clean it gets ... remember the scale build up on taps!

  • Further thought is that when it rains the rate of evaporation is zero whereas when using a hose the sun is probably not far away and evaporation rate is high - so tap water is more likely to leave deposits of scale. So a suggestion is to wait to hose until weather conditions resemble those when we get rain. Also using drinking glass monitors to see how much water has been given + extend the watering period by using a fine spray. Rain also waters the whole plant rather than just the roots. Plants probably need an extended time to take in sufficient amounts of water. Commented Jun 23, 2016 at 6:46
  • Rainwater contains Nitric acid which is an advantage ... but I equal up the score by adding fertilizer which comes naturally to us add does this more than equal the score! Natural human fertilizer also contain things which rainwater doesn't like potassium and phosphorus as well as nitrogen. At least a dilution of 1 to 20 is ideal. Commented Jun 23, 2016 at 7:09

Not the answer you're looking for? Browse other questions tagged or ask your own question.