How to Choose the Right Water Softener in 4 Steps
1. Determine your water hardness
Hard water contains a high concentration of calcium and magnesium. To determine how hard your water is, it’s best to purchase a hard water test kit from a home improvement store.
If you’re on city water, you can also contact your local water supplier for hardness information, as they may keep data records.
Most water hardness measurements are in mg/L (milligrams per Litre). To help choose a water softener size, you’ll need to convert mg/L into GPG (grains per gallon).
A “grain” of water hardness is equivalent to 1/7000th of a pound. Divide mg/L by 17.1 to convert it to GPG.
A mild water hardness level, in the 1-3 grain per gallon range, means there is some, but fairly little dissolved calcium and magnesium in your water.
Water that is considered very hard has 7-10 grains per gallon.
2. Know your average household water consumption
You’ll also need to know roughly how much water your household uses on an average day.
Average domestic water use is in the US is around 75 gallons per day, per person. But if your family uses more water (big laundry loads, long showers), water volume can quickly rack up to 100 gallons per person.
So if you have a family of 4 and everyone uses the average amount – your house’s water volume is likely to be upwards of 300 gallons per day.
3. Calculate Your Daily Softening Requirement
To determine the right water softener size, all you need to do is multiply your daily water usage by your water hardness:
- Multiply the number of people in your family by 75 gallons per day. This answer is your approximate daily water use.
- Multiply your water hardness GPG by the daily water use. This answer is your daily softening requirement.
Once you know this number, you can match it up with a water softener resin that has a similar grain capacity.
Let’s do a full calculation together: If we’re living in a 4 personal household and we each use roughly 80 gallons of water per day, we get to 320 gallons of total daily water use.
If our water is quite hard, around 8 grains per gallon, then we would multiply 320 x 8 to get 2,560 grains as our daily softening requirement.
Important to note: You need to adjust for iron if it’s also present in your water supply.
4. Pick the right regeneration frequency
The final step is to compare your daily softening requirement with a softener’s regeneration period.
Most softeners will function for multiple days between regenerations. They either regenerate on a set timer or contain a sensor to auto-manage regeneration.
Generally, water softeners have enough capacity to last 3-7 days between regenerations. Check your chosen product to find out how quickly it regenerates, then multiply this number by your daily softening requirement.
Example: If we know our softener needs to regenerate every 7 days, we can multiply our daily softening requirement by 7. 2,560 x 7 = 17,920. This is our final number, our required capacity in between regenerations.
4 or 5-person families will typically need a 24,000 or 32,000-grain capacity water softener, depending on the specifics of their situation.
Softeners that auto-modulate regeneration can use their salt more efficiently than softeners that regenerate on a set timer. Scroll down for more on the nuances of regeneration.