CH of 1125

[Leebo]

Reason I asked about the TA was to try to get a better feel for your fill water. I have seen areas of Arizona have low calcium in the fill but working from memory they frequently had low pH and low TA……

 

[Rancho Cost-a-Lotta]

It looks like you used a 10 ml sample for the pool water test and a 25 ml sample for the fill water. No problem there, but I'll just throw this out there with no reason to believe your testing methods are flawed. Make sure you're using the correct sample size and drop multiplier. It's a common error and I'm not sure if the K-2006 instruction card is clear.

For 10 ml sample, each drop = 25 ppm
For 25 ml sample, each drop = 10 ppm

 

[Sunnydaze]

So I just rechecked my fill water and the CH is 90ppm. So, still questioning what is causing the 2-year rise from 275 to 1125 CH, as that 90 fill water wouldn't really do it would it? We did get a lot of rain last monsoon season, but I would think that would lower it rather than raise it. Curing plaster during the first year could raise it, but from 700-1125 in the second year has me still wondering if a bad plaster mix may be the culprit, but please weigh in on fill cycles over a two year period in AZ, and how much 90ppm would typically raise the CH level?

Thanks!

What part of AZ are you in? I'm in chandler and we get our water from a mix of the Salt river and the Colorado river...our CH is 225-250. Only in the white mountains have i seen natural low calcium water.

 

[Great To Be Alive]

Sorry, a little slow on response, didn't see this had carried over to a second page!

I'm outside the Tucson area. To Mike's point, now I'm second guessing myself on the multiplier. But wait... I know I did it right, as I used 25ml sample for fill water, and did it twice. First time 8 drops and second time with fresh chemicals from a new K2006 test I received last week showed 9 drops, so 90ppm. I was surprised it was that low as well, and something feels wrong. I remember the plumber testing softness when he installed the water softener, and he got 14 grains. Quick Google shows 17.1 multiplier factor which would put my ppm at 240. The spigot that the pool is tied into isn't supposed to have been put through the soft water loop, but now I'm wondering if it was. That would explain my low ppm results on fill water, but wouldn't explain why my CH has risen so high... which is still my main question.

 

[Great To Be Alive]

Quick update. I triple checked CH at the house spigots, and they are all 90-110ppm. Checked an inside faucet, and the color never changed to Red, so no hardness. So outside spigots(pool) not plumbed through softener. I'm sure hardness changes through the year, but whether it's 90 in winter and a bit harder in summer, I still question where my high CH is coming from other than the plaster, which is a scary thought.

 

[mknauss]

Calcium came from fill water, chemical additives, or the plaster. Only places it can come from.

 

[Great To Be Alive]

In working through the numbers to determine if there is a potential issue with plaster, I came up with the following. Maybe this helps someone else as they struggle with rising CH as well.

• While my fill water currently tests around 100ppm for CH, the plumber set our softener at 14 grains two years ago when installed it and tested the water. At a 17.1 multiplier for PPM, that's around 240ppm. So hardness probably varies throughout the year, and may be highest during summer months when evaporation and refill is highest.
• If I use 200ppm CH as a benchmark for the fill water, and then do the evaporation calculations, it's not unreasonable to conclude that my pool water is completely refilled at least twice per year. Living in the desert and low humidity, combined with high winds at times... I have to think the .5" loss per day during peak heat months is probably conservative if anything. With the Baja step and average depth of the pool, I calculate around 2 complete refills each year minimum.
• Based on the above, and a starting CH of 275, I'm looking at an additional 800ppm over a two year period. That puts me at 1075 right there. Add in the fact that it's a new pool with curing plaster and my 1125 doesn't sound unreasonable after two years.

Let me know if the above looks sound to you all.

BTW: I inquired about RO treatment for my water rather than a drain and refill. I found a local company with a good reputation, and they charge somewhere in the neighborhood of $550 for the treatment. That's not too bad in my mind, especially when you consider all the water you are saving, not to mention the reduced risk of pool damage from draining etc. They can't do the RO unless the water is at least 77 degrees, and since I'm still able to balance the water while it's cold, I'll wait until spring and pull the trigger on the RO at that time.

Kind Regards,
Pete

 

[JoyfulNoise]

Pete,

How deep is your pool?

Where “outside of Tucson” exactly?? (Don’t worry, we’re not going to come knocking at your door trying to sell you stuff … although @mknauss and @Leebo are know to wear name tags and and dress in orange robes now and then …)

 

[Great To Be Alive]

Pete,

How deep is your pool?

Where “outside of Tucson” exactly?? (Don’t worry, we’re not going to come knocking at your door trying to sell you stuff … although @mknauss and @Leebo are know to wear name tags and and dress in orange robes now and then …)

I'm in Oro Valley. Backyard gets full sun most of the day, even in winter... and for some reason we get crazy wind at times. The pool is just over 5' at its deepest, sloping up to the stairs and Baja step. I'm guessing average depth to be around 3.5 feet when including the Baja step.

 

[JoyfulNoise]

I'm in Oro Valley. Backyard gets full sun most of the day, even in winter... and for some reason we get crazy wind at times. The pool is just over 5' at its deepest, sloping up to the stairs and Baja step. I'm guessing average depth to be around 3.5 feet when including the Baja step.

Ok. Oro Valley is served by it's own water supplier (not COT water). Most of your water (60-70%) comes from ground pumping aquifers with the balance made up by using CAP water (Colorado river water). Mineral hardness can vary quite a bit because you guys are butted right up against the Catalina Mountains. That system typically can range anywhere from 30ppm all the way up to 200ppm depending on the well location but the system does a pretty efficient job of mixing the water supplies to achieve a system-wide balance. You could probably measure your CH throughout the year and it will vary a bit, winter being lower than summer. There was a long time member here that lived in a large community association in Marana that had it's own well. Residents were charged a flat fee somewhere around $30 per month to run the community water supply (no metering charges) and the water had a CH of around 25-30ppm. Very lucky homeowners living there. I often threatened that there would a really looooooong garden hose running out of their community in my general direction and to not mess with it...

Second thing to understand about where we live - the general area of this part off the state of AZ gets about 10" of rain per year (if we are lucky) and has over 100" of water evaporation per year. This is measured using Class A Evaporation pans by the USGS as well as other more technologically sophisticated methods. But 100" of evaporation works out to about 8-1/3 feet of water per year. Your pool is an open water source and so it will loose 8ft or more of water per year simply due to evaporation. Given that your average depth is about 3.5 ft., that ratio of water loss to pool depth and a 90ppm CH source (probably higher than that on average), then your CH rise per year can easily be over 200ppm just from the fill water use alone.

My guess is that your initial estimates of CH based on Leslie's testing were probably off. Water that is very high in CH is also not easy to test as the endpoint can become very hard to distinguish AND the Taylor test is really not designed to work above 800ppm (too much droplet error and the indicator dye does not work well with high CH levels). You'd be better off diluting your pool water sample with distilled water at a 3:1 dilution (do it as accurately as you can) and then test the diluted water and multiply the results by 4.

Prescription is the same - you don't want to manage water with that high of CH. Mine got as high as 1500ppm and it was a bear to manage in the summer. If you think you are using a lot of acid now, wait until the heat kicks in and you need to keep the pH below 7.5 to maintain a low CSI ... you'll be adding buckets full of acid every other day. It's just not worth it.

• Drain the pool
• Refill
• Get the autofill line plumbed to softened water output OR use an RV water softener with your outdoor hose bib to add water to the pool

Also, the white flaking is caused by calcium scaling inside the SWG cell which happens because the pH inside the cell during chlorine generation is a lot higher than the bulk pool water. It can get as high as 10 to 10.5. At that pH, your CH is too high and calcium carbonate will be formed very easily.

 

[Great To Be Alive]

Ok. Oro Valley is served by it's own water supplier (not COT water). Most of your water (60-70%) comes from ground pumping aquifers with the balance made up by using CAP water (Colorado river water). Mineral hardness can vary quite a bit because you guys are butted right up against the Catalina Mountains. That system typically can range anywhere from 30ppm all the way up to 200ppm depending on the well location but the system does a pretty efficient job of mixing the water supplies to achieve a system-wide balance. You could probably measure your CH throughout the year and it will vary a bit, winter being lower than summer. There was a long time member here that lived in a large community association in Marana that had it's own well. Residents were charged a flat fee somewhere around $30 per month to run the community water supply (no metering charges) and the water had a CH of around 25-30ppm. Very lucky homeowners living there. I often threatened that there would a really looooooong garden hose running out of their community in my general direction and to not mess with it...

Second thing to understand about where we live - the general area of this part off the state of AZ gets about 10" of rain per year (if we are lucky) and has over 100" of water evaporation per year. This is measured using Class A Evaporation pans by the USGS as well as other more technologically sophisticated methods. But 100" of evaporation works out to about 8-1/3 feet of water per year. Your pool is an open water source and so it will loose 8ft or more of water per year simply due to evaporation. Given that your average depth is about 3.5 ft., that ratio of water loss to pool depth and a 90ppm CH source (probably higher than that on average), then your CH rise per year can easily be over 200ppm just from the fill water use alone.

My guess is that your initial estimates of CH based on Leslie's testing were probably off. Water that is very high in CH is also not easy to test as the endpoint can become very hard to distinguish AND the Taylor test is really not designed to work above 800ppm (too much droplet error and the indicator dye does not work well with high CH levels). You'd be better off diluting your pool water sample with distilled water at a 3:1 dilution (do it as accurately as you can) and then test the diluted water and multiply the results by 4.

Prescription is the same - you don't want to manage water with that high of CH. Mine got as high as 1500ppm and it was a bear to manage in the summer. If you think you are using a lot of acid now, wait until the heat kicks in and you need to keep the pH below 7.5 to maintain a low CSI ... you'll be adding buckets full of acid every other day. It's just not worth it.

• Drain the pool
• Refill
• Get the autofill line plumbed to softened water output OR use an RV water softener with your outdoor hose bib to add water to the pool

Also, the white flaking is caused by calcium scaling inside the SWG cell which happens because the pH inside the cell during chlorine generation is a lot higher than the bulk pool water. It can get as high as 10 to 10.5. At that pH, your CH is too high and calcium carbonate will be formed very easily.

Great info, Matt. Thanks a bunch for that! I'm curious now and will test the CH using the dilution method, when I have a chance to grab some distilled water.