single vs dual

[skiman]

So as I look to get best value, but also the best solution for a large home I am purchasing (7000 sf / 5.5 bathrooms / family of 5 with frequent visits from guests / inlaws), is it worth paying extra for dual tank setup, see that focus of the forums seems to be single tank setups, while I currently have a dual tank setup at my current residence (albiet a very old setup -- kinetico). So is it worth spending the extra $ on the Fleck 9100 SXT (dual), or should I stick with the Fleck 7000 SXT (single)?

Also any thoughts on the Autotrol 268 valve with 762 Controller (vs the Fleck)?

[greg-cws]

Have you had your water tested for hardness and iron yet? This information will help us to give you the best advice on choosing a softener for your home.

I definitely prefer the Fleck 7000SXT over the 268 with 762 control because the Fleck has fewer moving parts and the electronics are far more user-friendly.

I like twin tank systems, since they can regenerate at any time without downtime.

With a twin, you can also use smaller tanks (less resin) and squeeze maximum efficiency out of the system since you don't have to calculate reserves or schedule cleaning downtime.

The only disadvantage is that they do indeed cost more initially.

The ultimate twin IMHO is the Patriot Analyst (http://patriotwater.com/soft-water/patriot-twin-analyst/) - http://patriotwater.com/soft-water/patriot-twin-analyst/ This twin softener system uses the proven 9100 composit drive-train with specialized hardware software to control it. A new piston makes this an upflow (countercurrent) regenerated system which improves water quality and efficiency. This softener is able to sense the exhaustion-state of the resin media and automatically adjust to fluctuating water contamination levels. DISCLAIMER - The Patriot Twin Analyst is an IWP Product)

[skiman]

Finally got my water test results – hardness is 226 mg/L, iron is 0.06 mg/L and pH is 7.3. Calcium is 69.4 mg/L while magnesium is 12.8 mg/L.

So if I went with the Fleck 7000 SXT dual tank setup how many grains per tank would be ideal? More the better or can one have too much?

Thanks!

[greg-cws]

There is an old industry formula that is very handy for calculating system sizes:

Hardness x ((Number of people x 150) x 4))

After we convert the ppm to gpg and compensate for iron, the formula looks like this:

14 x (750 x 4)

This yields 42,000 which is the estimated system capacity (in compensated grains of hardness) your household will exhaust over 4 days of normal use.

We then up-size to the next largest system, which would be a 48 - 52,000 grain system.

So intuitively a 1.5 or 2 cubic system should work just fine if you went with the 7000SXT or SXTi platform.

If you went with the 9100TSi you could use a twin 32,000

[skiman]

Any advantage or disadvantage in going with twin 48,000 with the 9100?

[greg-cws]

On a twin platform like this, the difference between 32,000 and 48,000 comes down to space available and the need for higher flow rates.

Depending on the type of resin being used (kinetics, cross-linking, particle size and uniformity) the maximum flow throughput is generally determined by the area and depth of the resin column.

Industry standard gel resins have slower kinetics than some of the higher-end resins like the various iterations of Hydrolyte and other structured or specialized matrix resins like SST. With a slower ion exchange speed, more bed area and depth is required to allow higher flow rates. This was the origin of the "bigger is better" mantra espoused by many of the OEM's out there. I am very cautious when oversizing systems, because I believe that the liabilities of bacterial contamination due to improper/infrequent rinsing far outweigh the risk of high velocity hardness leakage.

In your case, the difference between 32,000 and 48,000 grains is approximately 0.5ft3 of resin which will allow for about 10% more throughput than with standard gel resin. Salt efficiency will be unchanged since this is a twin so I don't really see much of a benefit for you.

If you had significantly elevated iron levels, or hardness greater than 35gpg (approx 600 ppm) I'd definitely steer you to the larger tanks. I think you'll be just fine with a little 1 cubic foot twin.

[ion_avenger]

Hey Greg - I installed a twin analyst today and noticed there's a "deep clean" cycle in the manual now - is that just on the 9100TSi or is it on the regular Pentair 9100TS too?

[greg-cws]

TSi only, plus a host of other new features. We'll cover that on today's video conference call.