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Thread: Any downside to running an SWG pool with fairly high CH?

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    Aquatica's Avatar
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    Any downside to running an SWG pool with fairly high CH?

    SWG run pools seem to lose CH after a while due to backwashing so would it be a problem having a SWG pool with CH of 890?

    I can keep the water balanced but just wondering if there could be any side effects having CH of 890?

    Thanks.

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    Re: Any downside to running an SWG pool with fairly high CH?

    It is not ideal, but you can do it. The primary challenge is to keep the CSI from going too high and causing the cell to scale. Using a lower pH can help manage the CSI but it increases the rate of carbon dioxide offgassing.

    I would suggest the following if you are not going to lower the calcium.

    pH = 7.6 to 7.8
    TA = 40 to 60 ppm
    Calcium = 890 ppm
    Cyanuric acid = 60 to 80 ppm
    Salt = per manufacturer's specifications
    Borate = 50 ppm
    CSI = -0.1 to 0.0 for a concrete pool or -0.3 to -0.1 for a vinyl of fiberglass.

    What is the water temperature?
    Is this a concrete, fiberglass or vinyl pool?

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    JasonLion's Avatar
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    Re: Any downside to running an SWG pool with fairly high CH?

    The higher the CH level the more risk there is of scaling, especially scaling inside the SWG cell. You can compensate for that by keeping the PH and TA levels down, but it is much simpler if the CH level doesn't get that high to begin with. In some parts of the world, where the fill water has high CH level to begin with, you have little choice but to let the CH level get fairly high. If you aren't in that situation, it is best to not let CH ever get much above 500, and try to keep it below 400 if possible.
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    Aquatica's Avatar
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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by JasonLion
    The higher the CH level the more risk there is of scaling, especially scaling inside the SWG cell. You can compensate for that by keeping the PH and TA levels down, but it is much simpler if the CH level doesn't get that high to begin with. In some parts of the world, where the fill water has high CH level to begin with, you have little choice but to let the CH level get fairly high. If you aren't in that situation, it is best to not let CH ever get much above 500, and try to keep it below 400 if possible.
    Thanks for the reply. during the summer we get a lot of rain and have to backwash a lot so CH goes down. only need to fill in the winter months but even with that CH tends to go down. I never use CalHypo.

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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by JamesW
    It is not ideal, but you can do it. The primary challenge is to keep the CSI from going too high and causing the cell to scale. Using a lower pH can help manage the CSI but it increases the rate of carbon dioxide offgassing.

    I would suggest the following if you are not going to lower the calcium.

    pH = 7.6 to 7.8
    TA = 40 to 60 ppm
    Calcium = 890 ppm
    Cyanuric acid = 60 to 80 ppm
    Salt = per manufacturer's specifications
    Borate = 50 ppm
    CSI = -0.1 to 0.0 for a concrete pool or -0.3 to -0.1 for a vinyl of fiberglass.

    What is the water temperature?
    Is this a concrete, fiberglass or vinyl pool?
    right now water temp is 79F. this is concrete.

    how I am plan on setting the levels:
    pH = 7.5
    TA = 80 ppm
    Calcium = 890 ppm
    Cyanuric acid = 80 ppm
    Salt = 3,200
    Borate = 0 ppm (Non have been added as this is a new pool and no one on the island knows about borates)
    temp= 79F
    CSI = 0.07

    actually I could raise CYA to 100 in case pH drifts up to 7.8 the water will still be in balance. but I'd have to keep FC 4.5+

    overtime as CYA comes down and TA also the pH will eventually lock and won't move by then probably CYA will be 80 and I can keep it there and lower the FC.

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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by Aquatica
    right now water temp is 79F. this is concrete.

    how I am plan on setting the levels:
    pH = 7.5
    TA = 80 ppm
    Calcium = 890 ppm
    Cyanuric acid = 80 ppm
    Salt = 3,200
    Borate = 0 ppm (Non have been added as this is a new pool and no one on the island knows about borates)
    temp= 79F
    CSI = 0.07

    actually I could raise CYA to 100 in case pH drifts up to 7.8 the water will still be in balance. but I'd have to keep FC 4.5+

    overtime as CYA comes down and TA also the pH will eventually lock and won't move by then probably CYA will be 80 and I can keep it there and lower the FC.
    Using a higher pH and a lower TA will substantially reduce the concentration of carbon dioxide in the water and that will reduce pH rise and the risk of scaling. Using a pH of 7.5 and a TA of 80 will require much more acid to be added.

    You shouldn't increase the cyanuric acid to over 80 ppm.

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    Aquatica's Avatar
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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by JamesW
    Quote Originally Posted by Aquatica
    right now water temp is 79F. this is concrete.

    how I am plan on setting the levels:
    pH = 7.5
    TA = 80 ppm
    Calcium = 890 ppm
    Cyanuric acid = 80 ppm
    Salt = 3,200
    Borate = 0 ppm (Non have been added as this is a new pool and no one on the island knows about borates)
    temp= 79F
    CSI = 0.07

    actually I could raise CYA to 100 in case pH drifts up to 7.8 the water will still be in balance. but I'd have to keep FC 4.5+

    overtime as CYA comes down and TA also the pH will eventually lock and won't move by then probably CYA will be 80 and I can keep it there and lower the FC.
    Using a higher pH and a lower TA will substantially reduce the concentration of carbon dioxide in the water and that will reduce pH rise and the risk of scaling. Using a pH of 7.5 and a TA of 80 will require much more acid to be added.

    You shouldn't increase the cyanuric acid to over 80 ppm.
    some pools the pH locks in at TA of 80 and some TA of 60. seems its different for each pool so lowering pH weekly will bring TA down until pH locks in place. don't need much acid. Maybe 14 oz per week for a 15,000 gal pool. actually anywhere between 80-100 is actaully better as SWG % output can be reduced a lot more and this helps the cell last longer. I have some cells running at 20%. also depends on pump run time. but both need adjustment.

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    Re: Any downside to running an SWG pool with fairly high CH?

    put in 3 lbs of pH+ to raise pH and TA.

    pool went cloudy. this has happened before. DE filter usually clears it up over night and TA and pH is increased by morning.

    I think its the high CH that causes the water to cloud after adding pH+..

    client is coming back friday so hope it clears up. they want to swim but we are still waiting for the HeatPro pump..installing it as well as an Aqua Rite. want the water to be setup nicely for them.

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    Re: Any downside to running an SWG pool with fairly high CH?

    Using PH Plus wasn't such a good idea. That will raise both PH and TA. With the already high CH levels that could cause problems. You still have a little room, so I don't think it will be disastrous, but you are getting really close to CH scaling. JamesW was suggesting lowering TA with acid, just about the exact opposite of adding PH Plus.
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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by Aquatica
    some pools the pH locks in at TA of 80 and some TA of 60. seems its different for each pool so lowering pH weekly will bring TA down until pH locks in place. don't need much acid. Maybe 14 oz per week for a 15,000 gal pool. actually anywhere between 80-100 is actaully better as SWG % output can be reduced a lot more and this helps the cell last longer. I have some cells running at 20%. also depends on pump run time. but both need adjustment.
    The key to where the pH locks in is based on the carbonate alkalinity. To get the carbonate alkalinity, you have to subtract the cyanurate alkalinity from the total alkalinity. You have to subtract a percentage of the cyanuric acid based on the pH.

    pH.......% CYA
    7.0.........22
    7.2.........26
    7.4.........30
    7.6.........33
    7.8.........35
    8.0.........36

    This is especially important when your calcium is so high because the carbonate alkalinity could get to zero and your plaster would be at risk. For example, if you had

    pH = 7.8
    TA = 35
    Cyanuric acid = 100

    then your carbonate alkalinity would be zero and your CSI would be non existant. I suggest that you not allow the carbonate alkalinity to get to less than 20 ppm to allow some room for test error and fluctuations.

    Quote Originally Posted by Aquatica
    put in 3 lbs of pH+ to raise pH and TA.

    pool went cloudy. this has happened before. DE filter usually clears it up over night and TA and pH is increased by morning.

    I think its the high CH that causes the water to cloud after adding pH+.
    client is coming back friday so hope it clears up. they want to swim but we are still waiting for the HeatPro pump..installing it as well as an Aqua Rite. want the water to be setup nicely for them.
    pH increaser (sodium carbonate) should be avoided. It combines with the calcium to form calcium carbonate. When I suggested using a higher pH, I meant to allow it to rise on its own, not to increase it by adding anything.

    Using pH or alkalinity increaser one day and then using acid the next is counterproductive. You are just wasting chemicals.

    Since you will be heating the water, you should balance the water for the temperature you intend to heat it to.

    If possible, using borates would be especially good in this pool to help reduce the possibility of cell scaling. You would have to also subtract the borate alkalinity from the total alkalinity to calculate the carbonate alkalinity. For example if the pH = 7.8 and the borate = 50 ppm, then the borate alkalinity would contribute 10.2 ppm to the total alkalinity.

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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by JasonLion
    Using PH Plus wasn't such a good idea. That will raise both PH and TA. With the already high CH levels that could cause problems. You still have a little room, so I don't think it will be disastrous, but you are getting really close to CH scaling. JamesW was suggesting lowering TA with acid, just about the exact opposite of adding PH Plus.

    I was trying to kill two birds with one stone as owner wanted to swim as soon as possible. I did this in another pool and it worked out great. next day TA was up from 30 to 80 and pH from 7.0 to 7.8

    I prefer to adjust chems seperately normally. might have to add acid today to lower pH a little.

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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by JamesW
    Quote Originally Posted by Aquatica
    some pools the pH locks in at TA of 80 and some TA of 60. seems its different for each pool so lowering pH weekly will bring TA down until pH locks in place. don't need much acid. Maybe 14 oz per week for a 15,000 gal pool. actually anywhere between 80-100 is actaully better as SWG % output can be reduced a lot more and this helps the cell last longer. I have some cells running at 20%. also depends on pump run time. but both need adjustment.
    The key to where the pH locks in is based on the carbonate alkalinity. To get the carbonate alkalinity, you have to subtract the cyanurate alkalinity from the total alkalinity. You have to subtract a percentage of the cyanuric acid based on the pH.

    pH.......% CYA
    7.0.........22
    7.2.........26
    7.4.........30
    7.6.........33
    7.8.........35
    8.0.........36

    This is especially important when your calcium is so high because the carbonate alkalinity could get to zero and your plaster would be at risk. For example, if you had

    pH = 7.8
    TA = 35
    Cyanuric acid = 100

    then your carbonate alkalinity would be zero and your CSI would be non existant. I suggest that you not allow the carbonate alkalinity to get to less than 20 ppm to allow some room for test error and fluctuations.

    Quote Originally Posted by Aquatica
    put in 3 lbs of pH+ to raise pH and TA.

    pool went cloudy. this has happened before. DE filter usually clears it up over night and TA and pH is increased by morning.

    I think its the high CH that causes the water to cloud after adding pH+.
    client is coming back friday so hope it clears up. they want to swim but we are still waiting for the HeatPro pump..installing it as well as an Aqua Rite. want the water to be setup nicely for them.
    pH increaser (sodium carbonate) should be avoided. It combines with the calcium to form calcium carbonate. When I suggested using a higher pH, I meant to allow it to rise on its own, not to increase it by adding anything.

    Using pH or alkalinity increaser one day and then using acid the next is counterproductive. You are just wasting chemicals.

    Since you will be heating the water, you should balance the water for the temperature you intend to heat it to.

    If possible, using borates would be especially good in this pool to help reduce the possibility of cell scaling. You would have to also subtract the borate alkalinity from the total alkalinity to calculate the carbonate alkalinity. For example if the pH = 7.8 and the borate = 50 ppm, then the borate alkalinity would contribute 10.2 ppm to the total alkalinity.

    Thanks James.

    Good advice on using the future temp. I did not think of that.

    CYA is at 0 or maybe 10 hard to tell.

    It's hard to find enough baking soda on the island usually can only buy 1 lb at a time. also borax is very hard to find as well so sometime have to buy from the pool store pH+ and TA+.

    I will retest today and run the numbers through the pool calculator. once the water is balanced with the pool calculator the plaster should be at no risk right?

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    Re: Any downside to running an SWG pool with fairly high CH?

    I don't think you ever told us what the levels actually were in the pool to start with. Still, when you are dealing with high CH levels, the topic of this thread, you need to be very careful about raising either PH or TA. If TA was unusually low to start with it would have been better to use baking soda, rather than PH Plus to raise the TA, as that would have had much less impact on the PH.

    Baking soda is so much better for raising TA, that it seems likely that it will be worth purchasing even if that means getting one pound boxes at the grocery store. Of course, I don't know what the prices really are there, so I could be wrong.
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    Re: Any downside to running an SWG pool with fairly high CH?

    Quote Originally Posted by JasonLion
    I don't think you ever told us what the levels actually were in the pool to start with. Still, when you are dealing with high CH levels, the topic of this thread, you need to be very careful about raising either PH or TA. If TA was unusually low to start with it would have been better to use baking soda, rather than PH Plus to raise the TA, as that would have had much less impact on the PH.

    Baking soda is so much better for raising TA, that it seems likely that it will be worth purchasing even if that means getting one pound boxes at the grocery store. Of course, I don't know what the prices really are there, so I could be wrong.

    Thanks Jason. Pool was still cloudy this morning so added acid and it is clearing but pH back down to 7.3 and TA is 40.

    I don't think I have a choice but to replace water as setting the level seem to be near impossible with a CH of 890. Will meet with client this afternoon.

    another learning expereince but best to get CH down before wasting time and salt and CYA. need to set levels properly before installing heat pump and SWG. heat pump still hasn't reached the island yet anyway so got some time to work on balancing the water.

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    Re: Any downside to running an SWG pool with fairly high CH?

    client is ok with replacing water so have a sub pump in the shallow end. should take at least 50% of CH out. His fill water is R/O and has 0 CH so looks like everything is under control now. will bring up TA when water level is up and pump running again. then will check pH and adjust.

    then I can add CYA and salt.

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