In SLAM but CSI levels are off. CSI = "corrosion of plaster likely"

[steveb21]

I have been away for a few months so just sorting the pool out.

Water was green but having slammed for a week it has turned back clear - just a little cloudy.
I have CYA of 40, and have been shocking at FC 16.

I would say im not far off finishing SLAM (have previously completed a few on the same pool so I have an idea where I am) however having let the FC drop I thought I wold do some tests, results as follows:

FC 2.5
CC 0
PH 7.0 (could be lower, was the last reading on indicator)
TA 50
CH 200

CSI 1.35
(Calcite Saturation Index - requires pH, TA, CH, CYA, Temp, uses Borate, Salt
Less than -0.6 is suggestive of problems for plaster, tile, stone, and pebble pools.
Greater than 0.6 is suggestive of problems for all pools.)

Note: Mine is a fully tiled plaster pool.

Where do I start? shall I continue SLAM? or adjust to try TA, PH and CH and correct my CSI figure? Obviously worried about the plaster in my pool.

 

[JamesW]

Did your CYA disappear from the last time you checked it?

If yes, and the pH and TA have dropped during the SLAM, you might have been dealing with ammonia from bacteria eating the CYA and converting it into ammonia.

In any case, I would bump up the TA to 70 or 80 and continue the SLAM to completion.

What is the CYA?

What are you using for chlorine for the SLAM?

 

[steveb21]

The PH was approx. 7.2/7.4 prior to SLAM.
I did not take a reading for TA prior to SLAM.

Don't think I have increased TA before... will need to check if I have anything in garage.
I do have CH increaser, should I add this? I was going to get it to approx. 400... or it would affect the SLAM?

 

[jseyfert3]

Baking soda increases TA, but you probably need a lot more than what you might have in your kitchen.

Baking soda addition amounts can be calculated with Pool Math.

 

[JamesW]

I would add 2 kg baking soda (sodium bicarbonate) and continue the SLAM.

What is the CYA?

 

[steveb21]

Found some TA increaser (baker soda) in garage. To get to 70 I require approx. 1.5kg. I have added 500g and will retest shortly.

CYA - not had chance to get that reading yet, it has gone dark here in the UK. We are expecting a rare storm here tonight.

 

[JamesW]

I would add the full 2 kg and continue the SLAM with liquid chlorine. Brush the pool well to mix.

 

[steveb21]

Agreed.... however ive just got this thing where I always add additions slowly
What would be ideal TA range?

 

[JamesW]

Ideal TA is wherever it keeps the pH stable. I would suggest a target pH of 7.8 for normal levels.