Very Hard Well Water - Water Softener Okay?

[mark_in_atx]

I have a Pebble Sheen pool that is supplied 100% by well water. The chemicals got way off a while back and created scale all over the bottom of the pool, but the chemical systems are now working properly. I am not sure if the scale is a result of the chemicals being off or the well water, but essentially I am about to start from scratch and need some advice!

The Total Hardness (ICP Calc) as CaCO3 of the well water straight out of the well is 985, based on the well report.

I currently have a salt system but am considering switching to chlorine in order to help avoid future scale problems...I am concerned that the extra dissolved solids from the SWCG combined with the high TDS from the well water are a bad combination.

My options:
Chemical system options:
SWCG versus regular chlorine

Source Water Options:
well water as is
softened well water with water softener

It seems to me that while soft water has very little hardness, it has a very high TDS count per the sodium replacement of CaCO3. So no leeching because of the high TDS (primarily sodium) and no scale because of the low hardness (softened water)...at least that is my uninformed opinion. I feel like water softened well water with regular liquid chlorine should work really well in order to be well balanced and prevent as many issues as possible.

Are there any disadvantages to using soft water?

 

[jblizzle]

Welcome to TFP!!!

The SWG has no impact on the scaling ... other than helping the pH to rise more quickly. The presence of salt in the pool actually lowers the likelihood of scaling. If you test regularly and keep your levels in the recommended ranges, then scale is not possible.

We generally ignore the TDS numbers as it is much more informative to look at the components that make it up ... most important being CH and CYA among others.

Using soft water for top-offs is fine, but your system is not likely capable of actually filling the pool..

 

[linen]

Welcome to tfp, mark_in_atx

The Total Hardness (ICP Calc) as CaCO3 of the well water straight out of the well is 985, based on the well report.

Do yo know what the calcium hardness (CH) of the water is? If most of that 985 is CH, then that is high CH fill water. If refilling with low CH water is not an option (such as getting it trucked in since your softener most likely won't make a dent in your pool volume), then you will need to keep TA lower and watch your ph, so it does not go to high. See: http://www.troublefreepool.com/pool-school/calcium_scaling

As jbliz said, your swg is not the problem.

 

[mark_in_atx]

Linen: The 985 I referred to is the CH. Total Dissolved Solids (TDS) of the well water is 1490.

My assumption is that a SWG increases the TDS in water (not hardness, but TDS) versus liquid chlorine, for example. Is this correct????

If my assumption is correct, then the SWG aggravates the scaling problem by increasing the TDS. My understanding is that water saturation (low -> leeching, high -> scaling) relates to TDS, although for scaling to occur of course the water must be hard as well to supply the calcium. Thus with SWG the water is more likely to become super-saturated with TDS (more solids are added by the SWG although they are not hard solids, they are solids.) and thus the calcium scaling as a way to un-saturate to a level the water can handle.

In other words, are there scenarios (i.e. mine) where an SWG may aggravate the scaling versus liquid chlorine, although it is not actually the SWG causing the scaling, but a combination of multiple factors? If I am correct in my understanding the salt generated chlorine creates more dissolved solids than it seems to me this should be the case.

THANKS for any advice and clarifications!!!

 

[jblizzle]

I do not think your understanding is correct, but I am over my head

Like I said before we do not look at TDS, but rather the important things that make it up. If you look at the poolcalculator.com and input your current levels in the left column. Toward the bottom you will see the Calcite Saturation Index (CSI), this is what we typically look at when trying to balance the water. If this index get > +0.6 you are risking scaling. If it gets < -0.6 you are risking pulling calcium out of your plaster.

Why I think your understanding is not correct is due to observing the CSI when you change the salt content of the water. A bleach pool can easily have a salt content of 500-1000 ppm. But for a SWG pool, you will want a salt level around 3500 ppm. For a given set of parameters, if all you change is raising the salt content, then the CSI actually is reduced ... lowering the likelihood of scaling.

I do not understand the chemisty, but the use of a SWG does not appear to raise the risk of scaling due to the presence of the salt.

That said, a SWG will tend to cause the pH to rise more quickly than a bleach pool. If the pH is not monitored and corrected, its rise can very quickly result in the CSI rising too and possibly up into the scaling risk levels.

 

[chiefwej]

Wow, CH of 985 in fill water is very high. I start out about 375 but with the high evaporation rate here in the desert I'm at 1000 or so by now. My salt level is about 3700 and I have added borates about 50 ppm, so my TDS must be sky high. I keep my TA low (around 60) and watch the pH to keep my CSI in line. No scaling at all. So it can be done, but starting with CH as high as you are will be very difficult. Look for a source of fill water with a lower CH and use your softened water to top up the pool. That will make things much easier.

 

[cpwater]

I may not know too much about pool applications, but a quick read tells me that your pH got high enough to drop the calcium out, probably around 7.6 or higher. Adding heat of course aggravates that drop out as well. If your restarting the pool and you are using your softener to do so, make sure your softener can handle flowrate. Usually a 33kGr softener can handle a flow of around 5gpm, 45kGr - 7gpm, and 60kGr - 10gpm. I hate to say this but I also just read that if the cell in your SWCG is not maintained and cleaned regularly, the high calcium hardness in your well water would scale up the walls as well. Trust me though when I say that sodium bicarbonate and sodium carbonate will not scare even as a TDS above 10,000ppm.

 

[JasonLion]

My assumption is that a SWG increases the TDS in water (not hardness, but TDS) versus liquid chlorine, for example. Is this correct????

No, that is exactly backwards. A SWG transforms the chemicals in the pool from one form to another without changing the total amount at all. On the other hand, manual addition of chemicals of any kind always increases TDS.

On the other hand the TDS level is almost completely irrelevant. It won't make any difference worth mentioning what your TDS level is as far as calcium scaling goes. Calcium scaling is driven by several factors, most significantly PH, and also TA and CH, along with several other levels, while TDS only has a very tiny effect in comparison.