Plaster pool & CSI (not another CSI post..)

[alexsmith1]

Hi everyone,

New to the forums but finding everyone extremely helpful.. being a new pool owner I'm starting to understand the water chemistry *I think*..

My issue being CSI to ensure no calcium build up. I had to re-plaster (pebbblecrete) our pool due to the previous home owners destroying it with calcium.

Pool readings are:
Size: 45000 litres
FC: 3.4
pH: 8
TA: 70
CH: 340
CYA: 66
Salt: 5000
Water temp: 28c
CSI: 0.05

Now if I drop my pH down to 7.2-7.4 the CSI range drops between -0.7 & -0.52

Being summer I'm curious should I be leaving my pool pH in high 7's? A little bit of scaling has started that can scratch off. But the line seems to start growing along the waterline tiles. I just dont' want it ending up like the previous owners with calcium lines everywhere. Many thanks!

 

[mknauss]

With a SWCG it is best to keep CSI negative. That prevents scale build up on the SWCG plates.

Lowering your TA will assist.

How are you getting your test results? Some of the numbers are difficult to get with drop based test kits.

 

[alexsmith1]

Hi mknauss,

Are you saying having a CSI of -0.7 & -0.52 isn't a bad thing because of the SWG? With the pebblecrete.

FC, CH, CYA and Salt are from my local pool shops computer test system. As I don't have a CCL test kit (as we can't get Taylor kits in Australia) yet! Thank you

 

[mknauss]

Your CSI is best to keep between -0.3 and 0.0. Occasional drift below that is not a concern.

I would not trust a pool store tests. Especially for CYA, CH, and FC.

 

[alexsmith1]

mknauss, thanks for the prompt response. I understand everyones dislike for pool shops and trust me I'm not listening to them when they say my TA is too low! However, with the posted readings how do you suggest I manage a CSI in the suggested range?

Many thanks.

 

[mknauss]

Your pH should settle lower than 8 with a TA of 70. What is the pH and TA of your fill water? How much do you need to add for evaporation?

Maintaining a pH near 7.6 to 7.8 and letting your TA settle were it wants should keep your CSI in a good range.

 

[alexsmith1]

I haven't tested my fill water as I haven't needed to top up the pool. Thanks for the help.