Help me size water softener

igorek24March 3, 2014

Hi, I need some advice regarding correct size of water softener.

A little bit of background info: My house is 4000 sq feet wiht 4 bathrooms. There are 2 adults and 2 kids and our average monthly usage is 300 gallons of water based on water bill. Some of this water used by sprinklers, but I am not sure how to calculate that portion out. Water hardness is 35 gpg.

I need advice on which size of water softener would work for me: single tank Fleck 7000 96K grains, 3cu ft or Fleck 7000 110K grains 3.5 cu ft . Or should I consider some other size of softener like 64K or 80K or different valve (like Fleck 5800 -- I want to stay with Fleck). What about 64K, would it regenerate too often based on my water usage and hardness? Thank you very much.

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A little more information is required for correct softener sizing: pH, TDS at minimum. If you have any issues whatsoever with discoloration, iron and manganese are required as well.

Since you have a water bill, your water is treated at some point. You are entitled to a copy of the annual and quarterly reports. Obtain those - they may have the information you need. Many cities post their reports online. If so, post a link and I'll take a look.

A 2 cubic ft softener would regen every 3-4 days, which is too often on city water that exposes the resin to oxidating chlorine. I would avoid a softener larger than 3.0 cubic ft for residential use. Much of the time, residential water use happens in lots of short low-flow events which increases the probability of channeling (essentially this means water flowing through a narrow pathway rather than distributed over the whole resin bed). The larger the softener, the more chance channeling occurs.

    Bookmark   March 4, 2014 at 12:18PM
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Here is the link to our water quality report

So you think 3 cu ft system would be better for my needs than 2.5 cu ft (80,000 grain capacity)?

Thank you,

Here is a link that might be useful: 2013 Water quality report

    Bookmark   March 6, 2014 at 1:03AM
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Where did you get the 35 gpg hardness number? It is significantly higher than the maximum reported by your city report.

Softener sizing: Do you prefer to minimize salt usage or water usage, or are you looking for a good balance between the two?

    Bookmark   March 6, 2014 at 10:21AM
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Good balance between the salt usage and water usage would be best. As far as water hardness, I am in california and with drought I was told by one water technician that hardness of water is higher now than last year numbers indicate.

    Bookmark   March 6, 2014 at 10:47PM
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So I had a salesman for water softener company come in and he did some tests on water so I want to update wiht actual numbers.

Water hardness - 22
TDS out - 380
Chlorine - 1.5-2

He recommended 1.5 cu ft system but I thought with my water usage (38-40ccf /mo) it would be better to go with 2 cu ft system.
*** Does a 2 cu ft system make sense?
*** Should it be a single or twin tank system?

He also suggested filtering out chlorine as part of water softener (two tank carbon system). I asked if it is feasible to install a separate chlorine carbon block filter and he said a filter would drop water pressure significantly. He priced out filter + install at $575.
*** Is it true a separate chlorine filter drops water pressure much? Do I even need a filter?

My RO system had TDS of 600+. I just changed the pre and post filter but I don't think membrane was changed in a while and that's a problem. (its a 3 stage GE GXRV10ABL system) He offered
to replace filters and membrane for $250 total. We only use RO system for drinking and making tea.
*** Does this make sense or would I be better off just buying a new (and cheaper) system from Home Depot?

Thank you so much for all your help!

    Bookmark   March 7, 2014 at 2:50PM
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I'll address the RO first because it's the easy one. If your raw water TDS is 380 and the water guy got 600 on your RO water, there are a couple of possibilities. Either:

  1. The water guy failed to calibrate his TDS meter so the number is wrong.

  2. The water guy deliberately took a sample of the RO waste water in order to drum up more business.

  3. The effluent and waste water line from your RO are reversed.

Any of these cases should tell your guy doesn't know much about RO.


When we size a softener with water and salt usage in mind, we look for that sweet spot where regen occurs about once per week to keep water usage reasonable and regen with between 6 - 8 lb salt per cubic ft of resin to obtain good softening with reasonable salt usage.

In your case, the city reports a range of hardness. In order assure you never have a hardness spike, we need to size for the maximum of 26 gpg. The best size for salt and water efficiency would be a 2.5 cubic ft softener. It would regen every 7 days and use 63 lb salt per month. If you choose a 2.0 cubic ft softener instead, you could still regen evey 7 days, but use 78 lb salt per month.

A 1.5 cubic ft softener would be small. It would regen every 4-5 days which, when you have chlorinated city water, is hard on the softener resin. I don't recommend it.

Carbon filtration to remove chlorine:
This is not necessary, but some people object to the chlorine, so it is up to you. If your water guy is suggesting a softener with carbon in the softener (your description was unclear) don't do it - you will damage your softener resin.

A properly sized carbon filter will cause minimal pressure drop. A carbon filter that is too small will cause high pressure drop. A carbon filter can be either in the form of a cartridge filter where you change the cartridge every six months, or a larger media-bed filter (it will look like a softener, but won't need to regen, just backwash).

Regardless of where you choose to obtain your softener, you want the following for an industry standard softener. If you are looking for a non-electronic softener, Kinetico offers the more reliable options at a premium price (and you would need to deal with a local Kinetico rep). Any decent softener vendor should be able to provide the following:

  • High quality American or German made resin. This will provide a tight size distribution for optimal flow within the resin

  • Since you have CITY WATER: 10% crosslinked resin. The oxidizers that city water treatment plants use, such as chlorine or chloramine, are harmful to softener resins. Higher crosslinking will resist chemical attack longer.

  • Top basket. This serves two purposes. It sets up a proper water distribution during normal operation and prevents resin loss during backwash.

  • Gravel underbed. The gravel underbed is there to set up proper flow patterns, improve backwash, keep the bottom basket in place, prevent basket failure, and prevent...

    Bookmark   March 7, 2014 at 3:46PM
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Great post, thank you very much! This information helps tremendously.

Can you recommend specific models of cartridge and media-bed chlorine filter that would work with my house. Plumbing is 1" throughout house but downsized to 3/4" where hook ups to softener are.

    Bookmark   March 7, 2014 at 6:28PM
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Thanks to very helpful feedback. I purchased Fleck 7000sxt 2.5 cu ft (80,000 grains) system. Following the installation manual this is what my programmed settings look like:

C: 72
H: 25
SF: 10
DO: 8
B1: 10
BD: 60
B2: 5
RR: 10
BF: 53
FM: t1.2

Label on the valve states BLFC: 0.125 fpm

Please let me know if settings are correct to optimize salt use or how should I change it. Thank you.

    Bookmark   March 30, 2014 at 3:32PM
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  1. DF=Gal

  2. VT = St2b

  3. CT=Fd

  4. NT=1

  5. C=52

  6. H=26

  7. RS=SF

  8. SF=15

  9. RC=0 (You are using a % reserve rather than a fixed reserve)

  10. CR=0 (DonâÂÂt use variable reserve with iron in your water)

  11. DO=10

  12. RT=2:00 (or another convenient time when you wonâÂÂt be using water for a couple of hours)

  13. Regeneration cycle step times

  14. Ensure all days are set to ON, unless you have a specific day of the week when you do not want the softener to regen.

  15. CD doesnâÂÂt matter unless you set a day to OFF in step 14.

  16. FM You shouldnâÂÂt have to change this

  17. doesnâÂÂt matter

Exit Master Programming Mode.

Pour 7 gallons of water into the brine tank. Add salt.

Reset your clock to actual time.

At this point itâÂÂs a good idea to force the softener to step through the regen steps. There is no need to allow each step to complete. Just leave it in each step long enough to verify that the valve has changed position then move on to the next until you are back in service mode.

Enjoy your soft water.

    Bookmark   March 31, 2014 at 10:18AM
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Awesome, thank you very much!

    Bookmark   March 31, 2014 at 1:59PM
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I just updated the settings but there was no RC setting, SF is followed by DO. WIll this affect my settings and do I need any other adjustments?

    Bookmark   March 31, 2014 at 11:55PM
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RC drops off if you set a percentage for safety factor (SF). No further adjustment is needed.

    Bookmark   April 1, 2014 at 10:41AM
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Congrats igorek24. Very informative aliceinwonderland_id. I'm thinking of going the same route with the 7000SXT. Waiting for my water test results, then I will post in my thread (link below). Also, please check out my city's water quality report in my thread, and let me know your thoughts.

Here is a link that might be useful: My Thread

    Bookmark   April 16, 2014 at 7:11PM
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