Can You Use Tap Water For Hydroponics?

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One of the most common questions that I get from beginner hydroponic gardeners is:

Can you use tap water for hydroponics?​

It’s a good question!  When you’re just starting out, you want to get up and running quickly.  Your other options for water are all more complex than just using water straight out of the tap:

  • Distilled (costly)
  • Reverse Osmosis (costly, wastes water to produce)
  • Filtered (requires extra gear)

It’s no surprise that people want to use tap water for their hydroponic gardens.

But is it safe for your plants?

To answer this, we have to look at what happens to our water before it comes out of our tap.​  In terms of plants, one of the most important considerations is water chlorination.

What Is Water Chlorination?

Adding chlorine or hypochlorite to drinking water in order to kill bacteria and other microbes.  Chlorine is extremely toxic to these small organisms and water chlorination’s primary purpose is to destroy any diseases that could be transmitted in our drinking water.

That doesn’t sound too good for our plants and the various beneficial bacteria that live in our nutrient reservoir, does it?  It’s not…but there’s a secret.

Chlorine can break down if you leave your tap water out in the sun.​

It’s commonly quoted that chlorine will “evaporate” from water if you leave it out, but that’s not what’s going on.  The water needs to be exposed to UV rays from the sun in order to begin the breakdown process of the chlorine.

How Long to Leave Tap Water in the Sun?

In order to break down nearly all of the chlorine in your tap water, you’ll need to leave it out for about 24 hours.  Make sure you over-fill your reservoir to avoid losing too much water due to evaporation.

Chloramine: Another Potential Threat

​Chlorine isn’t the only additive you need to worry about.  Sometimes tap water is disinfected with chloramine.  If you’re growing in an aquaponics system then it’s especially important to rid your water of chloramine, as it’s toxic to fish.

What Is Chloramine?

Chloramine is a combination of chlorine and ammonia that’s used as a water disinfectant much like regular chlorine.  The difference is chloramine lasts much longer and is harder to break down.

This disinfectant is a lot harder to get out of your water, but it’s still possible.  The two easiest ways to make sure your water is chloramine-free is to run it through an active carbon filter (like a Brita filter) or use Campden tablets.

Campden Tablets can remove chloramine from your tap water

Campden Tablets can remove chloramine from your tap water

If you don’t want to use those methods, you can boil your tap water, but it’ll still take quite a while, so I don’t recommend this water.

Finally, you can also apparently use a chemical called sodium thiosulfate to break down both chlorine and chloramine, which is a very common tactic for those who own aquariums.​

One Final Consideration: Tap Water PPM

Now that you know how to rid your water of chlorine and/or chloramine, you probably think you can rest easy.

Not so fast.​

The last thing to consider is what ELSE besides pure H2O is in your water.  This is measured by the parts per million (PPM) of your tap water.

You may have heard of the terms hard water and soft water.

What Is Hard Water

Hard water creates that nasty buildup on your showerhead.

These refer to the amount of minerals in your water.  Hard water contains more minerals and is what leaves that nasty buildup on your shower head if you’re unlucky enough to live in an area where you have hard tap water.

How Hard Water Affects Plants

When you have extremely hard water, your plants can be at risk due to an overabundance of minerals that they only need in small amounts.  Some of the culprits here are calcium and magnesium, both minerals that your plants need to thrive…but they don’t need as much as the macro nutrients plants need.

A general rule of thumb is that water in the 200-300 PPM range is OK for your plants.  Anything higher and you may run into issues.

I like to test my water with a Bluelab PPM meter, which I also use to measure the PPM of my nutrient solution when growing plants as well, so it serves a nice double duty.​

So to answer the original question…can you use tap water for hydroponics?

Yes, yes you can – if you treat it properly beforehand!

  • If it’s chlorinated, make sure to leave it in the sun for 24 hours
  • If it’s chloraminated, use a filter or Campden tablets
  • If it has a high PPM, consider running it through a filter or mixing in distilled or reverse osmosis water to dilute the concentration.

If you’re interested in reading further about chlorine and chloramine, please check out this paper on removing both substances from brewing water.


The Green Thumbs Behind This Article:

Kevin Espiritu
Founder

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24 thoughts on “Can You Use Tap Water For Hydroponics?”

  1. Hi. I am learning a lot from you guys. I am currently gathering the materials I need to start in hydroponics.

    Thank you for this article, Kevin. It means a lot to start it right.

    God bless everyone.

  2. Thank you for the article! Please excuse my limited understanding of chemistry, b are there any filters out there that can help lower pH?

  3. First, check with your county, town, city water quality specialist. They all have one and you won’t get much info from the general customer service or payment section. Many also will test your water (at your outside tap) for things they don’t normally check like calcium and magnesium, etc. They routinely check for water hardness which if very hard can indicate plenty of calcium but it is better to know specific. In my area they try to keep the ph from 6.5 to 8, (mine runs 7.2-7.9) and hardness under 70 ppm – my last annual report indicated an average of 64 ppm which is moderately hard. My TDS runs between 89-109 usually right at 99. Some counties do this testing for free. Just about all are required to do and release annual testing results on water quality however somestimes they are up to 2 years behind on releasing as they collect and assimilate the entire year of data from each testing area and average it. Depending on your area’s piping, it can be different – most do a monthly testing at a location very near you. I live in a large county and there is a testing location on my streetb(which is only 2 medium to long blocks long).

    All of these factors need to be considered when doing hydroponics. Also our water quality specialist indicated the while chlorine can be evaporated or bubbled out with an air stone, chlorinamines can not and require specific filtration to reduce these levels – if it doesn’t say chloramines then it only does chlorine. The reason they are using chloramines is exactly to prevent that from happening. Chlorine is effective but highly unstable thus why it can be mostly eliminated with 24+ hours sitting. And as a point of information, using an air stone is a good way to add dissolved oxygen which is very beneficial. From your spigot watering you can use a high quality Dramm water breaker on your watering wand – is good with watering soil ground gardens and containers and greenhouse. However – if growing true hydroponics – your reservoir needs oxygen (bubbler based on volume) and being kept cool – generally not over 68-70F. Cold water holds more oxygen than water just as colder water will have lower TDS. See the dissolved oxygen white paper on their site or see Maximum Yield website and magazine for hydroponic growing.

    I have heard 1000 mg Vitamic C (absorbic acid) will neutralize a bathtub full of water but it is unstable and doesn’t last long. Some say orange slices in a glass of water will neutralize – note the word neutralize not remove like a specialty filter system will. I still have to research this with university studies and it’s effect on plants with hydroponics experts.

    If you grow hydroponically – you need to be using a good ph meter – I have Cole-Palmer Oakton 50 which can have the leads replaced thus less expensive than the whole unit. It isn’t cheap but I expect to have it for years, it is very accurate, has a wide base that holds storage fluid to keep leads wet which is important. Never turn wet units upside down – you will ruin the electronics – keep upright. Always rinse with distilled water and dry before storing in the storage fluid or calibration solution (so you don’t dilute them). Calibrate frequently including when you get it. Test strips are okay if accuracy isn’t as much of a concern or just have a small grow unit or like many of us – budget is low. A TDS meter is also an important tool which tells you the dissolved solids in the water essential to mixing nutrients and supplements to desired ppm – I have a H&M blue one (can’t remember model right now). PH of your water and your media is important as is knowing what ph range your plants like best. They all have their range example most orchids prefer 5.5-6.5, tomatoes like more acidic, snap beans more alkaline or base. PH is very important in terms of nutrients – each one has their needed ph to be taken up or absorbed by the plant. Other than nitrogen which has a wide ph range – the others have specific ranges. Find an accurate nutrient ph uptake chart. Some nutrients will have to have the water ph adjusted for just it, others you can find a sweet spot that will cover most of them. However some are just at the bottom or top of the sweet spot thus if you are having deficiency issues you may want to use those nutrients by themselves and adjusted appropriately. Keep in mind some chemicals can’t be mixed together, others have to be added to the water first, where some it doesn’t matter at all – it is all chemistry based. And you thought those chemistry and science classes in school weren’t important. All hydroponic nutrient companies should have a chart available for download and there are plenty on the web, though it may be helpful to utilize the ph ranges noted best by the company that makes the fertilizer. They are the only one who knows their formula and any proprietary ingredients not noted on the label. Most can also offer feeding charts and advice soecificnto your growing environment – check their websites for specific product information. It is useless to have say a calcium deficiency with appropriate symptoms and then to keep treating with calcium with no results all because your water/media ph has it locked out from uptake by the plant. Also whenever possible – try to use chelated nutrients and supplements – they work over a broader range of ph due to the addition of a metal – usually iron on the ones I have seen. And they seem to be more stable. Another point – if you aren’t doing the occasional pour-through ph testing (utilizing the distilled method) of your media – you might want to start. This is especially important with plants grown in media over a longer period of time like orchids, violets, etc. As media breaks down (whether spagmoss, coir, peat, etc) it becomes more acidic and less welcoming to your root system and will affect the effect of nutrient uptake/absorption. It may not be as important for short grows with fresh media each time. Know your media and mixes and whether they include nutrients and if they have been buffered with dolomite limestone or not. Check with the manufacturer as to the length of time before that buffering effect is nullified due to watering. Some like Besgrow Orchiata say 6-12 months but is dependent on water/feed schedule. But if you know what the media’s ph was buffered to at manufactur and you do a pour through test after a few watering to allow the media to be throughly wetted and then periodically – you will note the ph drop and it will help you know when repotting is needed. Some media is more acidic to begin with and all degrade and breakdown differently. Nutrients and water quality also cause an effect on the rate of breakdown and lowering of ph.

  4. Hi Kevin, what about A/C water to be use in kratky hydroponics? It’s also like distil water. Adding some drops of hydrogen peroxide to overcome any bacteria etc?

  5. Never had a problem with with chlorine or cloramine myself. My tap water comes out around 180 ppm of whatever is in it, I constantly aireate the reservoir and the make up reservoir. Have filled the reservoir added nutrients, phosphoric acid to adjust ph and straight to plants on a few occasions with very little lead time a few times when I was in a pinch and never had an issue. Nutrients I use are Masterblend

  6. Tap water in my home has TDS 180 ppm. Sodium content about 100 ppm.
    Does Na affect plants in ebb and flow hydroponics?

  7. I noticed that tap water conditioner also removes heavy metals such as zinc and copper. Those are trace elements qhich can be beneficial for your plants. Cant adding conditioner and then adding nutrients be counter productive and cause a deficiency?

  8. Laughable, almost every gardner waters their garden and vegetables in the minimal rain and the major growth time of Summer with water from the tap, via hose or watering can, and I don’t see many dead gardens from tap water…

    • This is an article on hydroponics, where ideally you control every aspect of your garden. That’s why the angle is to start with as close to pure water as you can, and then build from there.

    • The soil acts as a buffer for the plants and helps to filter out all the hard parts in the water. In HYDROPONICS that’s an entirely different story. No soil to filter out the various different parts of the water.

      So please next time before being snobby please do your home work. The person who wrote this article did a great job and took the time to deliver this information to us in a clear and concise manner.

  9. I don’t know if anybody ever done this. I just tried it out recently. I used a filter to get tap water to the reservoir and then use the tap water condition which used for aquarium to treat it. I don’t know if I am doing the right thing. My plants are still growing. Please share your experience.

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