Hardness bands by ppm
Very soft
0 to 70 ppm is far too little calcium and needs a mineral boost
Soft
70 to 140 ppm is the low end of useful. Add calcium
Slightly hard
140 to 210 ppm is generally fine
Moderately hard
210 to 320 ppm is acceptable at the low end and over-buffered at the high end
Hard or worse
320 to 530 ppm, and anything above 530, must be lowered or written into the fertilizer recipe
Ways to handle high minerals
Recipe around tap
Count calcium, magnesium and other tap salts as part of the feed instead of stacking a full bottle dose on top
Reverse osmosis
Force water through a tight membrane, then mix RO water with source water until the blend sits near 150 ppm
Heat drop-out
Warming carbonate water drives off carbon dioxide so calcium precipitates as scale. Pour off the water before it cools and redissolves
Soap check
Simple soap lathers in soft water and struggles in hard water. Modern soaps with softeners can fool the test
What a utility table is telling you
Calcium
A 4 to 20 ppm calcium range is a supplement signal, not a finished irrigation water
Magnesium
Reports near 0.8 to 5.6 ppm cover only a fraction of plant demand
Hardness units
Divide mg/L by 17 to convert hardness into grains per gallon
Meter pair
A combined pH and EC/ppm meter stops hardness and nutrient decisions from being guesswork
Other dissolved extras
Silica
Plants store dissolved silica between cells, which stiffens stems and helps against stress and insects
Sodium
Even modest sodium competes with potassium and calcium uptake when it climbs
Potassium in tap
Usually too little to feed the plant, but it still nudges alkalinity
Iron
Sometimes present in hard water and must be counted if the report shows it