Big mistake. Distilled water has a zero (0) ppm this means when you try to adjust the pH the regiment that you’re using (up or down) has nothing to stick to and can whack the pH in the soil pretty bad.
When using distilled water you’re better off just using the water and not ph’ing it.
This is an extremely high PPM for tap water. However, I can appreciate your wanting to save money. Just keep in mind that you’re waters 350ppm counts towards your total feed number when mixing nutrients.
Note
Since your water has such a high PPM coming straight out of the tap it would be very wise for you to visit your communities water utility website and obtain a recent water report
This will allow you to know what’s in your water both good and bad.
Mixing tap water with calcium magnesium (calmag)
You can rest assure there’s a percentage of calcium magnesium being put into your water system supplying you with Cal mag straight out of the tap.
However we don’t know what that number is. So we can use a conservative ppm number when adding the calcium magnesium (Cal mag)
How to mix Calmag
For now you’re simply watering your plants with a very minimal amount of water so I suggest you mix up at least 1 gal of calmag water
Fill up a gallon of tap water your tap water has calcium magnesium in it but we can add a little more as we don’t know how much is in yours so…
1 gal Tap water= 350ppm
Slowly add a few drops at a time of calmag to your gallon of water until your ppms rise up to 475 ppms. (This means you just added 125ppm of Cal mag to your gallon.
Do not adjust the pH in this water yet
This will be your storage gallon (so to speak)
Example
Let’s say you’re giving your plant 1 liter of calmag water.
1.) Simply pour your 1 liter of calmag water that you’re going to use into a cup.
2.) now you can adjust the pH of your 1 liter of Cal mag water to 6.5 pH
The reason we pH adjust right before feeding is because if you were to premix your calmag water and pH it by the time it was water day the pH would be out of whack.