# Softener for 6 units

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#### Maniac2k

##### New Member
First off, I know this is not the best way to accomplish this but its what the client wants.

Im having a tough time wrapping my head around this due to all the water storage tanks.

There will be 6 units with 2.5 baths each.
2 people per unit.
Each unit will have a 680 gallon cistern in the ground and a 265 gallon tank on the roof
The water source will be a well testing at 44gpg hardness.
The water will be processed through a sediment tank, carbon tank, and softener.
This processed water will be stored in a 2,650 gallon cistern in the ground and then fed to each units cistern and roof top tanks.

Thats a total of 8,320 gallons of stored water for 12 people.
At 60 gallons per day thats 11.5 days per unit when the tanks are full.

How would I size the softener?
Since the water is not being used on demand and has all the storage tanks, it would seem to me a smaller softener would work.

#### Bannerman

##### Well-Known Member
You didn't include a lab test report for the well water, so we don't know all of the water conditions including if there is any iron or manganese that will also consume softening capacity.

Assuming there is no iron or manganese present, with a considerable 44 GPG total hardness as tested, the 44 gpg will need to be multiplied by a factor of 1.3 to equal 58 GPG that will actually need to be programmed in the softener.

Since water will be consumed on demand from each cistern, to refill all cisterns will calculate as, 12 people X 60 gallons/day X 58 gpg = 41,760 grains Capacity per day.

2 cubic feet (2 ft3) of softening resin (64,000 grains total capacity) will efficiently provide 48,000 grains usable capacity when regenerated with 16 lbs (8 lbs/ft3) salt each regeneration cycle.

Because the cisterns may be refilled at any time throughout the day, it would be important for the softener to be capable of delivering soft water 24 hours/day, which would then require a twin tank softener with each resin tank containing at least 2 ft3 resin. With 2 ft3 resin in each tank, each tank will only provide only slightly more than 1-day capacity before regeneration will be required. While regeneration of the depleted tank is occurring, the alternate resin tank will continue to deliver soft water continuously.

To increase the amount of capacity to reduce the frequency of regeneration, consider a twin tank system with each tank containing a larger quantity of resin.

For example, 2.5 ft3 resin in each tank will provide 60,000 grains usable Capacity when regenerated with 20 lbs salt. 60,000 gr / 41760 = 1.43 days estimated between regenerations.

3 ft3 resin = 72,000 usable grains Capacity while regenerated with 24 lbs salt. 72,000 / 41760 = 1.72 days between regenerations.

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#### Maniac2k

##### New Member
Hi. Thanks for the response. No lab test report due to client restraints. We are far south of the border so things work very differently.

So no reduction in softener size should be taken into consideration due to the large storage tanks?

Does the recommended regeneration days for a dual tank system cut in half or remain the same?

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Hey, wait a minute.

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