Scaling on spa overflow with good water balance

[lnorris]

After adding salt to my pool, I've been getting noticeable scaling on the grout of my tile spa overflow. According to the pool calc, I have been well in the negative CSI range so I'm surprised this would be occurring. It's easily cleaned with 10:1 acid wash, but I would prefer to prevent than clean. Is this normal for any type of spillover that runs periodically? Do I need to adjust anything to better handle a spillover that runs 8+hrs a day?

My numbers:
FC 4
pH 7.5
TA 100 - this just recently went up from 75 in less than a week
CH 390 - this also has risen steadily from around 270 [plaster/pebble is about 6 weeks old now]
CYA 100
Salt 3200
Borate 50

CSI -.31 at 70F

 

[JasonLion]

Some scaling is unavoidable on any surface that routinely gets splashed with water and the water evaporates. I would not expect scaling on surfaces that are constantly, or 8 hours a day, under water.

I suppose it is also possible it is efflorescence, essentially something like scaling caused by water seeping out from inside through the grout when the spillover is turned off.

Another possibility: how carefully are you managing the PH level? The PH tends to rise fairly quickly when for the first several weeks. Scaling could happen if you have allowed the PH to get to high at some point.

A picture might help us figure it out.

Also, keep in mind that the PH, TA, and CH levels will all continue to go up, though perhaps more slowly. You might want to replace some water now to get the CH and CYA levels down a little so you don't have problems down the line.

 

[lnorris]

I've never let the pH go above 7.8 in the last few weeks that I have been montioring it, and I have been testing it daily. Should I drop to something closer to 7.2? That seems like it might be too low of a CSI.

I just cleaned it off yesterday, so it will take some time to build back up.

 

[JasonLion]

I don't think that CSI is related to the problem. If all the numbers you posted are correct you shouldn't be seeing any conventional calcium scaling.

You do have a couple of other things going on that will need attention soon: PH TA CH and temperature are all going to continue going up, and your CYA is too high. But none of those seem related.

I am thinking that it must be something else, like efflorescence, or something. A picture might help a lot, but that presumably needs to wait till the problem returns.

 

[lnorris]

Here are some shots of the early stages of the scaling. I'm starting to get in the habit of cleaning it off with acid every 2-3 weeks. CSI has been consistantly below zero.

 

[jkalan]

I'm curious to see what other answers are provided, but I have almost exactly the same deposit on the grout of my spillover. I believe it is efflorescence. Mine seems to originate on the seam between the grout and brick or elsewhere between grout and tile.