Pool School Recommendations for SWG Pool

[Johnl]

I am in the process of purchasing a SWG and was reviewing the Pool School recommendations for balancing water in a SWG pool. I was surprised the TA was listed in the 60-90 range, so I plugged in the recommendations into the Pool Calculator. When I did that the results came back that the water may be corrosive to plaster. Is that correct or am I missing something?

 

[257WbyMag]

CSI depends on several factors and TA is just one of them. Post your full test results for us and we can help you determine what adjustments might need to be made.

 

[Johnl]

Here are my current pool test results
FC - 3.0
PH - 7.5
TA - 155
CH - 275
CYA - 60
Pool calc results = .1 (Balanced)

Pool School Recommendations for SWG Plaster pools
FC - 3.0
PH - 7.6
TA - 90
CH - 300
CYA - 80
Salt - 3000
Pool calc results = -.31 (Potential to become corrosive to plaster)

The SWG is not installed yet, but I'm hesitant to make the changes recommended in the pool school because it seems to conflict with the pool calc results.

 

[JasonLion]

The CSI at some spots inside the SWG cell is far higher than it is in the pool. To avoid calcium scaling on the SWG cell plates it is good to keep CSI somewhat negative in the pool. Note that a CSI of -0.31 just says "Potential to become corrosive to plaster". CSI has to go noticeably lower than that before there is a real problem. Since a SWG tends to push the PH up, which increases CSI, it is quite unlikely that CSI will dip down into dangerous territory.

 

[Johnl]

Good to know. Thanks for the explanation.

 

[257WbyMag]

When you install your SWCG, you will also note that pH rise may be something that you might have to address more frequently than before. This sort of goes along with having a SWCG. It may be at this time that you find it beneficial to lower your TA some to help tamponade this pH rise trend to a certain degree. This is the benefit of having the pool calculator because you can see how adjustments in the values of certain things like pH and CH can affect your CSI. For example, lowering your TA may mean that you would need to compensate by adding more calcium to keep your CSI where you want it. Does this make sense?

 

[Johnl]

Yes, that makes sense. I'll probably avoid adjusting the CH higher because our fill water is 275 - 300 naturally and don't want that to get to high.