Your tap water will have particular properties according to where you live, the source of your water, and whether you have some sort of water softener or filtering system.
My tap water, for the sake of example, is from the public system and is considered ‘hard’ as long as it has a high mineral content. Rainwater is preferable as long as it’s missing things like excessive minerals or disinfectant chemicals, as long as you live in an area that was not subject to extremely acidic rain. I’m sure you heard about this. That said, this can change the chemical properties -such as the pH -of the soil which can affect plant growth, If I use tap water consistently on certain plants, To be honest I can see whitish rings of calcium deposits sitting on the soil surface. Just keep reading! Softened water has higher levels of salt than plants prefer, and these salts can build up in the soil.
Noone knows what’s inside the water since the contamination from human activities like car driving and industrial plant releasing exhaust fume from the chimney, in the end, rain water maybe good.
You may look for to have your personal judgement. Check this link, and this a great rain, It’s usually softer than tap water and soaks in the ground deeper than a hose watering. There are particles picked up in the atmosphere during a rain which offer nutrients to the soil that tap water does not have. Although they still grow when watered with tap water the results you get from watering with rain water are vastly improved. Chlorine and similar substances in mains water inhibit the uptake of nutrients and thus reduce plant growth and health. Rain water has a neutral pH.
Rain water is far superior.
The barometric pressure of the soil and atmosphere are lined up perfectly to allow for the rain to be utilized to have best results. Sahara. Rain however is readily absorbed by the soil and contains a few more nutrients it gains from the atmosphere. Our overuse of phosphates have helped to create soil that is out of balance. Of course our current water systems do not possess the full nutrient profile it once did. It ain’t good for plants or us. Now regarding the aforementioned fact… Consider the barometric pressure during a rain storm. Water from our public utilities and even water derived from deep water wells lack many things. We as a nation been using chemical pesticides since the mid 1940’s and studies have shown that it’s not very much what’s in the water but what really was now gone from the water.
Plenty of information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. My best guess is that plants may like electrolytes or charged particles more so than we understand. Unsourced material can be disputed or deleted.
Rainwater is generally better.
Rainwater is probably pretty much devoid of minerals. Therefore, they required less water and grew better when I filtered the water. 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. Known they certainly may harm the beneficial microbes in your soil, that will reduce the benefit you will gain from those microbes. Bleach and such. May not harm your plants in the drinkable amounts, per se.
because your soil may need those minerals, well water.
Has the potential to be better than rainwater, determined by your soil and the composition of the well water. I’m sure that the minerals in the water may have come from the abovementioned soil first and foremost, in part. Accordingly the minerals in the water may have come from the above-mentioned soil above all, in part. Because your soil may need those minerals, well water. Has the potential to be better than rainwater, relying upon your soil and the composition of the well water.