Water softener sizing - what do I need?

Discussion in 'Water Softener Forum, problems, installation and r' started by opto_isolator, Dec 19, 2013.

  1. ditttohead

    ditttohead Water systems designer, R&D

    Messages:
    1,871
    Location:
    Ontario California
    10 GPG is not that bad, but you will benfit from a softener. Also, the cause of scale is a lot more than the hardness. pH, temperatures, etc... all affect the scaling potential of water. I have fouled up membranes with scale in as little as 2 GPG of hardness. Steam boilers require <5 ppm of hardness, etc.

    Here is a great article explaining the low levels of hardness and their affects in a simple way. http://www.wcponline.com/pdf/1203Michaud.pdf
  2. ditttohead

    ditttohead Water systems designer, R&D

    Messages:
    1,871
    Location:
    Ontario California


    100% agree on this. Peak flow rates of systems are almost always very conservatively stated, and exceeding the SFR on a very rare occassion has almost no affect on a softeners longevity in a residential application. Of course, if you are constantly exceeding the systems design parameters, you will cause pre-mature damage to the media, but residentially, where the SFR may be exceeded very intermitently, and for very limited amounts of time...

    Day over-rides are nice, but for residential applications, I set them to 30 days. Small systems and tanks do not channel under normal conditions. It is the very large tnaks that tend to have issues due to low flow across too large of a bed area.

    Hope this helps.
  3. Gary Slusser

    Gary Slusser That's all folks!

    Consider that I have seen 2-3 gpg of hardness cause problems with fixtures and water heaters. Especially problems with oil, gas and tankless water heaters which are very expensive. People with electric water heaters tend not to see what that hardness causes them but it increases their cost of operation and maintenance which is usually premature replacement. And if the softener is not removing all the gpg of hardness, it usually happens when showers or washing machines are being used so, that hardness is mostly going into the water heater because hot water is being used. And the damage is internal and not noticeable, but it's there, and in increased fuel bills and eventually it will cause premature heater failure in most cases.

    The odds are... my customers do not exceed the constant SFR gpm I told them to expect because they look in the history of their Clack control valve to see the max gpm that has been run through their softener. I have yet to have any of them find I was wrong, although some get real close to going over it, and I ask them to look and I ask if they think the softener has always given them 0 gpg soft water. Without running low or out of salt, they always say yes.

    I have never sized based on all fixtures' max gpm as if all fixtures were running at once. But plumbing codes do call for that. I size based on the type of fixtures and how many bathrooms and the number and ages of the people living in the house and how they use water. IOWs, real world water use.

    Using a bucket etc. to try to determine flow rate means you have to run all the fixtures into buckets at the same time, you can't physically measure it by running one at a time. All fixtures but tubs and toilets have a federal government max flow rate; that's the numbers I mentioned previously and will be your peak demand.

    The Pentair flow rate figures are for their control valve, not an entire softener.... If you go to any resin manufacturers' web site and look up the SFR on their resins you will normally see a range of 1-5 gpm per cu ft.

    My figure of 9 gpm constant SFR for a 1.0 cuft softener is all but twice their figure so I don't see that as a conservative figure. The SFR of a control valve is to be used to determine IF that control valve can service the size tank being used, and the cuft volume of resin dictates the size of the tank and that dictates the control valve that can be used. Example, a 5600 can be used for up to a 12" dia tank for a softener (2.0 cuft) and up to a 10" dia tank for a filter (1.5 cuft). The valve speck sheet also shows the pressure losses at X continuous and peak gpm and that is mostly used to compare one valve to another. Many people mistakenly think otherwise but, I would like to know how anyone can size for constant SFR 99% of the time.... And if you can do that, I have to ask why not 100% of the time? That's like saying that removing all but 2-3 gpg of the hardness is OK. Or with a filter, to not get all the H2S or all the iron out is OK.
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