CSI and balanced spa water

[daveooph]

Does the csi number matter for above ground spas or is that more important for inground pools?

Reason I ask is my,hot tub is at -.8 csi. Partially because my TA is 40. But for some reason having the TA any higher than that causes the PH to always be around 8.

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[pooldv]

Is it a stand alone fiberglass tub? No, CSI is not important. Especially not a negative CSI. It is only important in plaster pools and spas.

 

[daveooph]

Is it a stand alone fiberglass tub? No, CSI is not important. Especially not a negative CSI. It is only important in plaster pools and spas.

Yes it is a stand alone.

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[JoyfulNoise]

If you added 50ppm borates to your water, then you might be able to raise your TA up to 50-60ppm since the borates will act as an additional pH buffer. Then you can probably get your CSI a little higher.

 

[daveooph]

If you added 50ppm borates to your water, then you might be able to raise your TA up to 50-60ppm since the borates will act as an additional pH buffer. Then you can probably get your CSI a little higher.

Any advantage to do this or since csi isn't a problem should i leave as is?

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[pooldv]

Borates are a nice add for a variety of reasons. We use them in our pool and hot tub. Here is a write up on borates, Borates - Why and How.

Here is the process we have used for two years to maintain our hot tub, How do I use Chlorine in my Spa (or pool)?, we are very happy with this method. We also add epsom salts.

 

[JoyfulNoise]

Any advantage to do this or since csi isn't a problem should i leave as is?

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It is highly recommended to use them in a chlorine spa. Borates add to the buffering capacity of the water and are very good at slowing down pH rise. In a hot tub, as you have found out, you typically want to keep your TA low as the outgassing of CO2 from the hot, jetted water creates a large pH rise. The problem is, if TA is too low, you can crash it to 0ppm and, in turn, crash your pH as well. So borates not only add buffering capacity against pH rise but also let you operate at a lower TA without fear of crashing the pH. They are also considered a supplemental algaecide and so you might see reduced chlorine demand using them as well.

As pooldv pointed out, there is a sticky on the use of chlorine in hot tubs and part of that sticky talks about the benefits of adding borates.