[GpsFrontier]

Hello Davephan,

I plan to start off with tap city water and let it sit for a day or two. I assume that letting it sit before using it will improve the water for growing plants.

No, not at all. The only thing letting the water sit does is allows any chlorine in the water to dissipate. The excess mineral salts will continue to remain in the water forever. Even if you let it sit so long half of it evaporated, all that would happen is the excess mineral salts would become twice as concentrated because you cut the water volume in half.

At what point in time to I measure the pH and adjust the pH?

It's best to check and adjust the pH before and after you add the nutrients. As a new grower, you should check the pH every day. As you gain experience you will begin to understand how and why the pH fluctuates or changes. Eventually you will be able to predict pH changes and you wont need to check pH every day. You should adjust the pH anytime it's out of range.

I'm not sure if there is a optimum time to let the water sit before using it.

The chlorine should dissipate in a day or two, it will dissipate quicker if you use a air pump and air stone to aerate and circulate it. If you cant smell the chlorine anymore, it's likely all dissipated.

Would filtered water from my refrigerator or using a filtered water pitcher like Brita or Zero Water be better than using city tap water?

Absolutely, as for your refrigerator water, that depends on the quality and how often you change your refrigerator water filter. Often people use a inline filter, but the refrigerator often has one inside as well. Most of the time people forget to change the one inside, and the inline filter is behind the fridge so nobody even sees it to change it.

As for Britta and Zero water, again much better than tap water. and most likely even better than the refrigerator water. Zero water would be the better than Britta because it has a 5 stage filter that includes a ion filters needed to take out dissolved solids. Britta just uses carbon filters, and you need ion filters to take out dissolved solids.

After the pH is tested, adjusted, and re-tested, the hydroponic fertilizer is added. Does the pH need to be measured again, and the pH re-adjusted again?

As I mentioned earlier as a new grower you should check pH daily until you understand how and why pH changes and fluctuates. Over time you will begin to be able to predict when and why the pH changes. Then you won't need to check it daily, by then you'll know when you should check it. But that takes experience, and you only gain experience from doing.

As a Hint. If you get the General Hydroponics pH drops, the directions say to fill the vile 1/2 way and add 2-3 drops. What I do is fill the vile about 1/6 and use 1 drop. In other words, instead of using 3 drops, I use 1/3 the water and only one drop. you get the exact same color, just less water. Don't worry you don't need to be exact measuring, and it's easy to read the colors. In fact If you look on the right side of this section of this page pH adjusters, I created a visual color scale. I did the typical 1/2 vial and 3 drops for the pictures so it's bigger. But I only need 1/3 the water and one drop to test pH like I mentioned.

Does adding the fertilizer change the pH.

It can, That depends on the pH of the water, the mineral salts already in the water, and the specific composition of the nutrients. As well as pH buffers in the nutrients. Most commercial nutrients for hydroponics have pH buffers. The buffers help keep the pH stable longer. If your waters starting pH isn't that far off, the buffers usually wind up making the pH perfect at 6.0. On the other hand I have used nutrients that drooped the pH down to below 4.0. So it just depends. You'll eventually learn how your specific nutrients affect the pH.

After the nutrient mix is created, how often does the pH need to be retested and re-adjusted?

Again I would recommend any new grower check pH every day until they become experienced with it. When things are going right, typically the pH should remain stable for a good week or more. But things like the actual water volume relative to plant size, how big the plants are and how much water the plants are drinking up will quickly affect pH. Again, that's part of the experience I mentioned. I wrote this article What size reservoir do I need that will help explain how the water volume affects nutrients and pH swings.

Is there a way I can determine when to add more nutrient as the plants consume the nutrients?

EXPERIENCE....EXPERIENCE....EXPERIENCE....
Watching your plants and paying attention to changes will tell you exactly when the nutrients are depleted. New baby leaves will start turning light green/yellow. That means the nutrients are depleted. There could be other reasons for leaves turning yellow, but experience will tell you if the yellowing may be a result of other issues, or it's just time to change the nutrients. Water volume relative to plant size, and water uptake are factors that affect how long the nutrient solution will last. Again those factors are explained in the "What size reservoir do I need" article I posted a link to above. Observation and paying attention to your plants daily is how you gain experience.

I assume there is a way to test for the nutrient concentration.

That is called a TDS/PPM/EC meter. While some people can't live withough't a TDS/PPM/EC meter, to me their just a fun toy to have if you have the money to spend. The one thing I want them to be able to do, they cant do, so I don't bother using them. Plants don't take up nutrients evenly, they take what they need and leave the rest. This means that some nutrients are used up faster than others. The TDS/PPM/EC meter cant tell you which ones are in the water and what concentrations each are in (witch is the one thing I want them to do). That means some elements are depleted more than others.

When you use a TDS/PPM/EC meter to adjust and bring back up nutrient concentrations, your adding a balanced nutrient to an unbalanced nutrient solution. So now the nutrients that were depleted most are still somewhat depleted, and the ones that weren't used as much are now in excess. Because the TDS/PPM/EC meter cant tell you what is in the water, only the total combined value of everything combined, it cant tell you how unbalanced it is. If you just keep adding nutrients back to bring the TDS/PPM/EC meter reading to a specific level, over time the nutrient solution will become more and more unbalanced to the point where the nutrients the plants use most are very deleted, and the others are at toxic levels. Even though your TDS/PPM/EC meter readings are in the right range. That's why I don't bother with them. A good TDS/PPM/EC meter will cost over $100, and I can buy enough nutrients to make 5,000 gallons of nutrients for that. So I'd rather have the nutrients to grow plants with than neat toys.

About how long would the nutrient last before throwing out the mix and starting with a new batch?

Again, EXPERIENCE....EXPERIENCE....EXPERIENCE.... But in general typically 1-4 weeks. It has everything to do with water volume to plant ratios. As well as environmental conditions. That's why I wrote the article What size reservoir do I need to help explain those factors, and explain how water and plant size are related.