Return to the Plumbing Forum | Post a Follow-Up

Water Softener Sizing (Once Again)

Posted by mokh (My Page) on
Tue, May 8, 12 at 19:42


Would appreciate if anyone can help guide me to getting the appropriate size water softener. Below are the details.

Well Water
2 persons/2.5 bathrooms/Dishwasher/Washer/Normal Showers/1 Large bath tub (no jets)
SFR from the large bath tub (13.63 gpm)
Iron <.05 mg/L
Magnesium 4 mg/L
Calcium Hardness as CaCO3 158 mg/L
Magnesium Hardness as CaCO 16 mg/L
Total Hardness as CaCO3 175 mg/L
pH 7.7
TDS 396 mg/L

I have been recommended a 40,000 grain / fleck 5600L. The fact they never even mentioned the resin cuft tells me a lot about the dealer after I started researching. I've used a few online calculators that seem to suggest 1.5cuft would be enough, but I am concerned about the SFR. The fleck 5600 seems like a proven valve so I dont mind using that but the size is a major concern.

Really appreciate your opinions in advance.

Oh yeah, my floor space available at the softener hookup is 31in x 40in.

Follow-Up Postings:

RE: Water Softener Sizing (Once Again)

Based on the values you posted you'll need a lot smaller softener than 1.5 cu ft but that will severely cramp your SFR.

A 1.5 cu ft softener generally give you 12 gpm peak SFR. Around the size softener you need you'll get 7 gpm.

Are you sure the SFR at the tub is 13 gpm?

What size is the plumbing at the place the softener will be installed?

RE: Water Softener Sizing (Once Again)

The plumbing is one inch at the softener hookup.

The large bath tub i took the sfr from is much faster than anywhere else in the house, I'm not sure why/how. Did it again and it took 22 seconds to fill a 5 gallon bucket. So about 13 gpm I believe

An outside hose hookup is 5 gpm and the other tub that has a mixing valve of hot/cold water was 2.8 gpm.

Thanks for the quick reply.

RE: Water Softener Sizing (Once Again)

Where are you getting your concerns about SFR? Do you think your pump can't keep up? Low water flow? Not sure what your research has shown but I know of only one or two people on the internet who use SRF religiously. Although it can be an issue under extreme cases, in most situations it is not.

In fact SRF is really only relevant immediately after regeneration. And if you follow the advice of many to rate your softener to regen every 8-10 days (till full max capacity), then what started out as 12 gpm SFR is reduced to next to nothing prior to it regenerating. My advice is to regen more often at a lower salt dosage to reduce the chances of hardness bleed through.

If the dealer did an adequate job in selecting the appropriate equipment, mentioning the actual cubic feet of resin in the softener (along with dozens and dozens of other technical datum) is not necessary unless you ask and they don't want to tell you. Then I would be a little concerned, but the vast majority of new customers have little interest or knowledge of those details. If you want to know, simply call the dealer and ask---he should be more than happy to give you all the tech info you request.

After seeing thousands of customers, I have practically never had one ask me about the volume of resins, even when doing upgrades or changing from single tank to twin tanks or vice versa. Of course if they ask, I would explain. When I got estimates for AC units, I never asked what the BTUs were or what compression settings were going to be. I just wanted to be sure it did the job.

The FLECK is a reliable valve and there are others on the market that also do great work.

RE: Water Softener Sizing (Once Again)

I wouldn't use a 3/4" valve (5600) on a 1" line. The Fleck 7000SXT would be a better choice.

"Not sure what your research has shown but I know of only one or two people on the internet who use SRF religiously. Although it can be an issue under extreme cases, in most situations it is not"

Using a tub that flows 13 gpm with a correctly sized (for the water conditions) softener that provides 7 gpm peak flow and filling the tub with hard water IS an issue in my mind. When you pay for soft water you ought to get it... every drop that flows.

The number of people who do something wrong will never make it right. The right way is the right way regardless of whether practiced by the minority or the majority.

Regardless of any salesman's opinion, resin manufacturers publish specs referencing flow rates based on resin volume and tank size. When flow exceeds those specs then hardness leaks through and that is physics, not opinion and has little to nothing to do with salt dose or regeneration frequency.

RE: Water Softener Sizing (Once Again)

I didn't know he had 13 gpm need at his house. But that still doesn't explain even if he had a gigantic softener (12 cubic foot) softener and it was nearly exhausted with only a few inches of resin capacity before it goes into regeneration and suddenly you push 13 gallons per minute through it, you would find it impossible to prevent hardness leakage.

It doesn't matter how big a softener is, if you let it go too far before regenerating and then suddenly call for a great demand, you will get hardness through. SFR is based on when a softner has just regenerated (100% capacity) not just before (10%) it regenerates.

If you shoot a bullet into a phone book of a city of hundred thousand people it might make it to the Wilsons (no hardness leakage) but if you shoot another bullet through the same hole, it will blast right out the other side right past the Zyzskis almost as if nothing were there (definite hardness leakage).

I don't oppose the so called SFR but it must be taken for what it is worth and understood and applied accordingly.

RE: Water Softener Sizing (Once Again)

"It doesn't matter how big a softener is, if you let it go too far before regenerating"

When you under size your softeners and then regenerate them very often that is a real concern.

When a softener is sized and set up based on the water conditions, water use, and plumbing requirements then that is a very rare occurrence IF ever.

"I don't oppose the so called SFR but it must be taken for what it is worth and understood and applied accordingly"

And that is exactly what I'm doing.

RE: Water Softener Sizing (Once Again)


How often do you fill the tube at that water flow? You must have a one inch line to the tube. Can you tell?

RE: Water Softener Sizing (Once Again)

Thank you both for your replies.

We recently bought the house, but the tub will not be used very often, maybe three times a year. I can't tell the piping to the tub but when you turn on the hot and cold water at the same time it's amazing the rate it comes out compared to any other place in the house including outside faucets.

I wasn't aware the 5600 was only a 3/4 line, thanks I missed that one. The local dealer says they dont recommend digital valves as the Arizona heat here tends to cause failure faster, any opinion on that, it seems reasonable.

In my situation would it be better to choose a middle choice in between the right size softener vs service flow rate? Maybe a Fleck 7000sxt 1.25 cft? I would like to have 100% soft water to the showers, dishwasher and refrigerator. I suppose I could go lower to a .75 cft with the trade off that the tub will over run the flow rate of the softener. That may be the right choice instead of wasting salt and/or water.

RE: Water Softener Sizing (Once Again)

There are more complicated electronics in your car, motorcycle, and air conditioner than in a softener control valve... even in AZ and there is an electric motor in a Fleck 5600 Econominder. If the softener is going to be placed outside there are environmental covers available for many control valves.

In order to get 13 gpm at that tub someone understood SFR for what it is worth and applied it accordingly... most likely a plumber and not a softener salesman.

If you accept the demands of the big tub two or three times a year then a .75 cu ft softener would do nicely albeit with 7 gpm SFR.

RE: Water Softener Sizing (Once Again)

I would like to get the softener ordered today. What would be the disadvantage of having a 1.25 cu ft when we only require .75 cu ft.

Can I not set the softener to think it is smaller? Is that feature on every valve (fleck)?

If it was your place what would you do? A kid may be in the short future.

Thanks again.

RE: Water Softener Sizing (Once Again)

That flexibility is the reason to buy a contemporary electronic control valve. They have the flexibility to easily make those adjustments.

You could get a 1.25 cube softener and set it up to function as if were smaller. You lower the K by adjusting the salt dose. As long as the max days between regenerations is 6-7 days with 8 day override you should be OK. Don't forget to calculate for reserve.

 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Plumbing Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here