What size water softener for 5 people with 20 gpg water?

5 people, 20 gpg hardness

80k grain

7,500 grains a day — regenerating about every 7.1 days

Softener sizethe number on the label is the maximum, at the worst salt efficiency	80,000grain
Grains removed per day5 × 75 gal × 20 gpg	7,500grain
Water used per day	375gal
Days between regenerationsaim for about 7 — much longer and the resin bed channels	7.1days
Usable capacity67% of nameplate, at an efficient salt dose	53,600grain
Salt per regenerationat 3,500 grains per lb — an efficient dose	15.3lb
Salt a yearabout 20 bags of 40 lb	782lb

Notes

**Size by grains per day, not by house size.** A softener does not care how many bathrooms there are — it cares how many grains of hardness pass through it. 5 people at 75 gallons each through 20 gpg water is **7,500 grains a day**, and everything else follows from that one number.
**The number on the box is the maximum, not the working capacity.** A 80k unit only reaches 80,000 grains at the highest salt dose, where salt efficiency is at its worst. Run at a sensible dose it delivers about **53,600 grains** per cycle — which is the figure used above, and the one your salt bill will reflect.
**Regenerate roughly weekly.** Stretching the cycle to save salt lets the resin bed sit loaded and channel, so hard water finds a path straight through a softener that looks like it is working. This size regenerates about every 7.1 days.
**Add iron to hardness before sizing.** Every 1 ppm of dissolved iron behaves like roughly 4 gpg of hardness. A well at 20 gpg with 3 ppm iron is really sizing at 32 gpg, and skipping that step is the most common reason a correctly sized softener still delivers hard water. At this hardness the margin for that mistake is already thin.
Get a real water test first. Municipal water reports publish hardness for free; well water needs a lab, and the lab will also give you the iron and pH figures that decide whether a softener alone is even the right equipment.

5 people, 20 gpg water

7,500 grains a day. That calls for a 80,000 grain softener, regenerating about every {kq.chukỳ} days and using roughly 782 lb of salt a year.

Size by grains, not by house

A softener does not care how many bathrooms there are. It cares how many grains of hardness pass through it.

5 people at 75 gallons each through 20 gpg water is 7,500 grains a day, and every other number on this page follows from that one.

The number on the box is the maximum

A softener only reaches its nameplate capacity at the highest salt dose — where salt efficiency is at its worst.

Run at a sensible dose it delivers about 53,600 grains per cycle, using 15.3 lb of salt. That is the figure used above, and the one your salt bill will reflect.

Regenerate roughly weekly

Stretching the cycle to save salt lets the resin bed sit loaded and channel — so hard water finds a path straight through a softener that looks like it is working.

Add iron to hardness before sizing

Every 1 ppm of dissolved iron behaves like roughly 4 gpg of hardness.

A well at 20 gpg with 3 ppm of iron is really sizing at 20 plus 12, and skipping that step is the most common reason a correctly sized softener still delivers hard water.

Get a real test first. Municipal reports publish hardness free; well water needs a lab — and the lab also gives you the iron and pH that decide whether a softener alone is even the right equipment.