3 grains per gallon: what it means for a household of 4
| The same number in ppm3 gpg × 17.1 | 51mg/L |
|---|---|
| Classificationnoticeable on glassware, rarely worth softening | slightly hard |
| Mineral through the pipes per year300 gal/day at 51 mg/L | 47lb |
| Grains removed per day3 gpg × 300 gallons | 900grains |
| Days between regenerations, 32,000-grain unitabout 24,000 usable grains at an efficient salt setting | 26.7 |
| Salt used per yearabout 3,500 grains removed per pound of salt | 94lb |
Notes
- Two units, one number, and everyone mixes them up. 3 gpg is 51 ppm — multiply by 17.1 to go one way, divide to go back. Water utilities usually report ppm, softener manuals want gpg, and a softener set on the wrong one is out by a factor of seventeen.
- 47 pounds of dissolved mineral a year is the number worth holding on to. That is calcium and magnesium carbonate passing through the plumbing of a 4-person house at this hardness. Most of it leaves with the water; the fraction that does not is what coats the heating element, narrows the pipe and dulls the shower glass.
- Where it lands first is the water heater. Scale settles on the bottom of a gas tank between the flame and the water, so the burner has to work through an insulating layer, and on the elements of an electric tank until they overheat and fail. Flushing a few gallons off the drain valve once a year is the cheapest maintenance in the house and almost nobody does it.
- At this hardness a softener is a solution looking for a problem. Below about 3.5 gpg there is little to remove, and softened water at this level adds sodium and a slippery feel for no real gain. Spend the money on a test for what is actually in the water instead.
- Iron changes the sum, and it is not on most reports. Every 1 ppm of dissolved iron adds roughly 4 gpg of load to a softener, so 3 ppm of iron on 3 gpg water behaves like 15 gpg. Above about 3 ppm — or at any level once the pH is over 7 — a softener is the wrong tool entirely and needs a filter ahead of it.
- Test strips give you one number badly. A lab test costs little and returns hardness, iron, manganese, pH and total dissolved solids together. Those five decide the equipment; the strip decides nothing.
3 gpg is 51 ppm, and that is slightly hard
The two units are the same measurement wearing different clothes. One grain per gallon equals 17.1 milligrams per litre of calcium carbonate. Utilities report ppm; softener manuals want gpg; a unit programmed with the wrong one is out by a factor of seventeen.
47 pounds of mineral a year
That is what passes through the plumbing of a 4-person household at this hardness — pure arithmetic from 51 mg/L and the water actually used. Most of it leaves with the water. The fraction that does not is what coats the element, narrows the pipe and frosts the shower glass.
Where it lands first
The water heater. In a gas tank scale settles between the flame and the water, so the burner works through an insulating blanket; in an electric tank it builds on the elements until they overheat. Draining a few gallons off the valve at the bottom once a year is the cheapest maintenance in the house, and almost nobody does it.
What to test before buying anything
Hardness, iron, manganese, pH and total dissolved solids — one lab test, five numbers. Iron matters more than people expect: each 1 ppm adds roughly 4 gpg of load to a softener, and above pH 7 a softener cannot hold it at all.
Nearby sizes
- 2 grains per gallon: what it means for a household of 4
- 5 grains per gallon: what it means for a household of 4
- 1 grains per gallon: what it means for a household of 4
- 7 grains per gallon: what it means for a household of 4
- 3 grains per gallon: what it means for a household of 3
- 3 grains per gallon: what it means for a household of 5
- 3 grains per gallon: what it means for a household of 2
- 3 grains per gallon: what it means for a household of 6
Read more
- Water Still Hard After Installing a Softener — Seven CausesTest the outlet before blaming the unit. Half of these faults are a setting, and one of them is that the softener was never plumbed into the line it was meant to soften.
- Water Softener Installation Cost by State — 48,000 Grain, All 51Only 35% of this job is labour, so the state spread is just 26%. A quote at double the figure below is not explained by local wages.
- Well Pump Short Cycling — It Is Almost Always the TankMotors are killed by starting, not by running. A short-cycling pump can burn out in months, and the cause is usually a tank that costs a fraction of the pump.
- Orange Slime in the Toilet Tank Is Not Iron — It Is Iron BacteriaA filter removes iron. Nothing filters out a colony that is living in the well casing, and that distinction decides whether the money you spend does anything.