Water Softener Downsizing

[System48]

Our county is bringing online a nanofiltration system what will reduce our hardness from 22 GPG down to 8 GPG. I have been using a 64k capacity system for last 10ish years without too many issues and wanted to sanity check my sizing for a new system. The sizing math I did would put me at a little under a 24k system, for some overage I'm going for a 32k system.

I'll be reusing a 7000sxt valve and will be buying a new brine and resin tank. I'm looking at a 9" x 48" resin tank and a 14" x 36" square brine tank. For resin the best price I've found on a 10% is for Aquatrol CAT110E.

I didn't have much time to plan or research when I did the original system, it was a new construction house and we didn't find out we had very hard water until a couple days after closing.

 

[Gsmith22]

why downsize? you existing system will just regenerate less if there is a drop in hardness of the incoming water.

 

[Sponsor]

 

[System48]

why downsize? you existing system will just regenerate less if there is a drop in hardness of the incoming water.

A few reasons, I'll have improved salt efficiency with a more appropriately sized system. I'd be forcing a regen at 14 days at the most and at 64k I'd be wasting roughly half the capacity based on my usage. Add on to that, due to poor planning and worse maintenance my current resin is nearing the end of it's life so I need to replace it anyways. Lastly, I'm also moving to a tankless heater and I'm going for a better plumbing layout and a smaller brine tank will help.

 

[Bannerman]

Municipal water suppliers often obtain water from multiple sources, each source typically with a different hardness quantity. While you stated your water currently contains 22 gpg hardness, if that hardness number was obtained from the municipality, it will most likely be an average hardness amount from all sources, not necessarily the hardness arriving at your specific location.

Even if the new supply system is successful in providing 8 gpg hardness to your location, suggest configuring your softener for 10 gpg hardness since supply hardness will often vary throughout the day, especially during early weekday mornings when water usage is normally greatest while most people are preparing for work/school.

Since you will not know when hardness may increase/decrease, it's recommended to anticipate some increased capacity depletion so a softener will be usually programmed for 2-3 gpg higher than the hardness amount tested at that location.

When a softener is programmed to regenerate when less than the resin's total capacity has been exhausted, then substantially less salt will be required, which will greatly improve salt usage efficiency (Hardness Reduction Efficiency).

The usual recommendation is to size a system so regeneration will not be required more often than 1X per week, to as few as 1X per month while configured for efficient salt usage.

The usual recommended settings for efficient operation is 8 lbs salt per ft3 resin to regenerate 24,000 grains per ft3 as that will provide the best balance of efficiency (3,000 grains/lb), usable Capacity (less frequent regenerations) and high soft water quality. For greater efficiency (3500 grains/lb), some choose 6 lbs salt/ft3 to regenerate 21,000 grains capacity per ft3, but the tradeoff is more frequent regenerations (more water per month/year needed for regeneration) and slightly lower water quality (higher hardness leakage through the resin).

Since your existing 2 ft3 softener currently functioning properly, assuming there are only 2 users, to ensure the usable capacity has been utilized within 30-days, your existing softener maybe programmed to regenerate when as little as 34,000 grains capacity has been depleted. To regenerate 34K grains capacity will require only 8 lbs salt total (4 lbs per ft3 resin), thereby resulting in a salt efficiency of 4200 grains per pound of salt.

Compare chart below:

 

[Reach4]

You can cut the brine fill minutes to about one third of what you have been using. Set DO to 30 days.

Never use the "64K" and "32K: marketing numbers in calculating, as Bannerman pointed out.

 

[System48]

Thanks Bannerman and Reach4. Is there any concern in having the brine tank sit stagnant for potentially up to 30 days when using carbon filtered municipal water?

 

[Reach4]

None that I have ever read. 30 day DO is commonly recommended for city water.

 

[System48]

Finally getting my system put back together and setting the new timings but had a question regarding salt grids. When figuring out the salt dosage do I need to take the salt grid into consideration? In my brine tank it takes 3 gallons to get the water level above the grid, I know eventually salt does make it below the grid but do I consider that 3 gallons below the grid into my math or not?

 

[ditttohead]

Do not figure the grid into the math, you have a timed refill so 5 gallons of water is 5 gallons of water... grid or no grid your valve will put in the same amount of water into the brine tank.

 

[Reach4]

No, that will not affect the settings.

The brine sucks down to the middle of the air check valve each time, so that is the base you start out.

Initially, you want to fill to that height, and add the amount of water that will be injected each brine fill (BF). Or just fill the to the middle of the brine valve.

If the top of the grid may be at the same level as the middle of the brine valve. May be higher, or may be lower.