Total Dissolve Solid (TDS) Meters only provide an approximation of "Total" dissolved solids. To decide on proper water treatment and filtration (if at all) you need some more data. This article will teach you how to know exactly what's in your water and understand some of the important terminology in water quality management. 

Knowing your water quality is easier on city or municipal water sources. If you're on a well, this may be more difficult, but you can still find out! We'll start with my personal FIRST STOP to know what I will be dealing with on local water. Even if you're on a well you'll want to know the water quality or surrounding cities. In the second half of the article I'll talk about how I manage learn about well water sources.

What's in your City or Municipal Water?

Once you've found a property that meets your requirements, you'll need to know about the water's constituents. Not just Total Dissolve Solids, but how much of each mineral. This will dictate filtration and treatment plans for your grow facility. My first stop is local water quality reports using GOOGLE.

City’s nameANDstateAND “Water Quality Report”

Notice I use quotes and upper case AND. These are operators for google and force the search to include exactly those search items.

Below is the results for a random city in California. Remember, I’m in Colorado, so this is how I would research a setting up a random grow. 

Googling Water Quality Report

The Second choice was a .pdf file for a 2016 Water Quality Report. Once opened, the file includes a lot of info, but I would scroll through until I got to data tables, as shown below:

Here you can see the minerals of concern, units measured (ppm or ppb) and a list of different regional sources for that water supply. It's important you understand the difference between ppb ("parts per BILLION"; ~micrograms/L) and ppm (Parts Per Million; ~mg/L). Hopefully you the heavy metals, organohalides, etc are in "ppb".

The values I immediately check out are “total dissolved solids” (TDS), “hardness”, Calcium, magnesium, Sodium, Iron, silicate, iron and water treatment. Here’s the values found from our example city:

If you look around, you’ll see the Total Dissolved Solids is in the 300 - 600 range depending on source. Then if you look under specific components, you’ll see Boron "seems" high, but if the units are ppb (parts per billion, 1000x smaller than ppm...and negligible; and a plant friendly dose, by-the-way).

Here’s a table of what I’d document for this source:

Component Units Min. Average Max. Average
Total Dissolved Solids ppm 54 548
Chloride ppm 38 80
Calcium ppm 11 78
Hardness (as CaCO3) ppm 42 402
Magnesium ppm 3.7 60
Silica ppm 4.7 11
Sodium ppm 13 60
Chloramine (chlorine) ppm 0 4.1


Next I would want a sample tested, but with this info, I can easily make decisions on how to manage my water. San Jose's publication suggest the TDS will be 400 ppm +/- 200 ppm and this could include unwanted amounts of sodium and chloride. For a drain-to-waste grow or soil grow there's a chance you wouldn’t need Cal/mag if at 80 ppm Calcium and >20 ppm Magnesium..and depending on you nutrient line. I would probably still add silica for mothers, veg, and early bloom in soil or drain-to-waste.

This water could do great with Coco coir or peat which would buffer these doses of minerals. If I planned on a recirculating systems, I may fill up my hydroponic systems with this water, but top up with treated reverse osmosis, rain or water collected from a dehumifier or Air-conditioner (whichever was most available). Conservation of water is always key. CAUTION: Some of these collection methods require water treatment for safety.

Assessing Well Water

If you’re moving to a property with well water, you will still want to look up municipal water quality reports from your area because these values often gives you an idea of what minerals are lurking in the aquifers, but I would NOT rely on this without doing some more research and actual testing. First start with a google search: 

"City" AND state AND "well water" AND testing OR Report

For our sample city "San Jose" you see our results below: 

The Second and Fourth Article were both valuable: 

The Second linked helps you know where you can have you well water tested. I would also send my municipal/city water to one of these labs for testing. Here's What I found: 

The fourth link in the google search was an official Santa Clara Valley Water District publication called "A GUIDE FOR THE PRIVATE WELL OWNER", shown below. Keep reading, it contains information on the recommended tests AND costs :) 

If you check the Table of Content, you see page 12 "WATER QUALITY SAMPLING AND TREATMENT". If you jump to page 12 you find the following table of valuable information.

Between these two publication, you now know what costs you're looking at and where to have a sample of your well and municipal water sent. You'll find this information for most geographical regions. If not, email us and we can recommend a great testing lab for agricultural water quality. 

For more information on Water Quality and Treatment, check out my article Hydoponics Water Quality and Treatment--A MUST READ!

Thanks for reading! And reach out anytime with questions or comments. 



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