Rain water from your roof is subject to gathering pathogens, bacteria, and airborne fungi and spores that are on your rooftop and in your rain gutters. Especially through bird droppings, dead insects, as well as infected foliage that builds up. Well water is subject to gathering pathogens, fungi, ground minerals, as well as soil born pests and diseases. Either one untreated could cause problems. I would filter them to get out minerals and spores ("absolute" 1 micron sediment filter to catch spores). Then either use UV light or chemical treatment (like bleach or chlorine) to kill the remaining live microbes, bacteria, and fungi.

HomeHydro, you once again show the great depth of your knowledge in Hydroponics. You made it very clear that both rain water running off my roof, and well water are both not the best for plants. May I ask what water you use, and how you test, and treat it? I have access to the lab at the water company I work for , and can get my water tested by them if need be.
The rain from the sky appears to be the best, but very little of it can be gathers by just gathering what hits my rain barrel, if I had one.
Can you say with any certainty that any pathogens, or other micro organisms that are in my water, will end up in the vegetable, or fruit that I grown with it?
Maybe you are saying that the impurity's of the water will make the plants susceptible to problems, such as disease?
Maybe I am better off with city water that has its PH adjusted after the nutrients are added. The chlorine quickly dissipates, especially with the aeration.
Is it true that my well, which comes from 120 feet, and produces very little iron deposit, and zero sulfur, is full of bacteria, and pathogens?
On another note, my cucumber plants are growing the fastest of all that I planted from seed. I will have flowers shortly. The radishes grew the second fastest. My tomato seedlings are doing well if kept in partial shade, but the plants that get the most sun are dying. It appears that I could save some of them if I reduce the exposure to direct sun light.
We have had 97 degree days with bright sunshine, and high humidity. I would put some of these plants off until after winter, or maybe sooner in the fall, but our weather has been like everywhere else, not usual Winters that are usually short and have two weeks of near 30 degree weather, are now many months of on and off cold weather. We sometimes get s freeze of ground covering (grass) at a time that snow birds would be coming back and wanting to go to the beach. I'm going to be prepared and covers my plants with a frame and plastic sheeting. I may even stick a couple of light bulbs under the plastic to keep some heat on the plants. I will be ready to address that when the time comes.

Hello massimj,
Thanks for the kind words (the checks in the mail), although I don't think of myself as more knowledgeable than other people. I just try to help others when I can, and just try to pass on what I've learned, as well as my experiences (I just hope others will do that for me too). I use RO (revers osmosis) water myself, although it is a pain to get enough out of the system. I usually need to start gathering water the day before I need it. I cant really use our outside tap because we have extremely hard water. And our inside tap goes through a water softener.

I understand it costs about $75 to have the water tested. I don't test the water being that it's RO water. And we have the system serviced twice a year, so I'm comfortable that it gets out enough excess minerals. To be honest I'm not 100% sure the RO system catches 100% of pathogens and bacteria (though I am sure it catches fungi spores). But I'm pretty sure the water treatment plant (city water) gets about 98% of them before the water gets to the RO system. Even so, for the cost of having the water tested I can build a UV light treatment system (and eventually will). Not really for source water issues, but for airborne contaminate issues.

I grow everything outside, so my systems are still subject to lots of potential airborne infiltration. So my plan for building a UV light system (when I have the extra money) is fairly simple. It involves using a section of tubing (rain gutter, down spouts etc.). Laying it flat, cutting an opening large enough for the light. Hot gluing in a section of durable clear glass (to keep the light from getting wet accidentally). Then using a small pump to pump the water through the tube. I will probably use a ball cock valve inline from the pump to control water flow, and a short dam on the other end to control water depth. Basically setup like a NFT system, but using UV lights in place of the baskets with plants, and a section of durable clear glass to separate the water from the lights (for electrocution safety). I can add more lights or use one long fixture (increasing light contact time) to be able to increase water flow depending on how large the reservoir is.

Can you say with any certainty that any pathogens, or other micro organisms that are in my water, will end up in the vegetable, or fruit that I grown with it?

Without testing it nobody cant say what pathogens are in the water, or what numbers they would be in. The term "Pathogens" is a fairly generic term for any microorganism that's harmful to you, animals, or plant life. But there are beneficial microbes as well. It's not that pathogens make it into the food you eat and you ingest them (like if you drank the water), but that they damage and/or cause disease to your plants. Like pathogens, there are beneficial bacteria, and fungi that are good for your plants too, as well as harmful ones that cause disease to your plants and/or damage fruit. But without specific testing, or visible signs of their symptoms, there's just no way to tell witch are actually present, and/or in what numbers.

Maybe you are saying that the impurity's of the water will make the plants susceptible to problems, such as disease?

Basically water impurities: Excess minerals can through off the balance of nutrients in your nutrient solution, and could cause mineral toxicities and/or nutrient lockout. Pathogens, fungi, and bacteria can cause plant and root diseases. And a unhealthy plant is also more susceptible to pest infestations.

Is it true that my well, which comes from 120 feet, and produces very little iron deposit, and zero sulfur, is full of bacteria, and pathogens?

Every well's water is different, but all well water contains traces of whatever is in the soil around the well. There's just not really any doubt there are microorganisms (both good and bad), bacteria, and fungi in your well water (even soil born organisms), as well as in rooftop collected rain water if it's untreated. But the question is more about weather there are more bad (pathogens, fungi, and bacteria), than beneficial ones. Beneficial ones will usually be able to keep bad ones in check (minimal to no noticeable damage/symptoms). But it's more of a question of if the bad ones out number the beneficial ones or not. If so, they can breed and multiply uncontrollably, and that's when you'll notice a problem.

There's just no way to tell which ones are present, and/or what numbers their in from just by looking at it, or using a EC/TDS/PPM meter. The meters only measure total "mineral content" (and not live organisms at all), but meters cant tell you which minerals are actually present, and/or how much of "each" there is either. If you have access to a lab to test your water supply for free, or at least a substantially reduced cost, that is great. I would take advantage of that. I just cant justify spending the money to check for live organisms when I can build a UV light for the price of just one test.

For a commercial hydroponic setup I plan to build, I'll be using use city water (outside tap), but plan to build a multiple cartridge water filtration system for it. Mainly because even high volume RO systems waste water, and I don't want to waist large volumes of water. For that filtration system I will probably have the water from it tested by a lab from time to time (especially for mineral content). Then check the water coming out of it regularly with a EC meter for "irregular readings." For pathogens, bacteria, and fungi issues, each hydro system will have it's own UV light treatment. I also plan to use beneficial microbes in the system as well. I'll leave the UV lights off for a couple days for the beneficial microbes to become established. Then when I switch the UV lights on, the microbes traveling under the light will be killed, but the ones in the growing medium will be able to bread and help fend off any pathogens living in the growing medium at the roots.