salt water pools

[Nerone]

New salt water pool owner. Everything was great during the summer.
Now it looks like I have a "rough" coating all over the plaster lining of my pool. Possibly Calcium coating? Does anyone know what this is, how to get rid of it and how to avoid it in the future.? Thank you

[carolyn]

Nerone,
What is the size of your pool and how much salt are you using? What you are seeing is probably salt buildup. If you don't think you are using too much salt, the problem could be that the controller needs to be re-calibrated or the anodes are bad. Contrary to popular hype, salt water pools can be a big pain in the butt! Email me if you need to know more. I've been in the pool business for 20 yrs. and, believe me, I have seen everything.

[chem geek]

If you haven't been monitoring your pH, it's quite possible that it rose and that what you are seeing is calcium carbonate scaling. Most SWG pools tend to rise in pH unless you do things to mitigate that such as maintaining a lower TA, minimizing sources of aeration, use a higher CYA level (60-80 ppm) with an FC that is at least 5% of that level (the higher CYA is only needed if the pool is not covered and in full sun), and use 50 ppm Borates as an additional pH buffer (and algaecide). These latter two factors normally let you lower your SWG on-time and that reduces the rate of pH rise. The lower TA and less aeration directly reduce the rate of pH rise (pools are essentially over-carbonated and outgas carbon dioxide which causes the pH to rise; the TA mostly measures that degree of carbonation).

Though salt buildup can occur from splash-out outside the pool, it sounds like the rough coating was on the inside, below the water line, and that does sound like calcium carbonate scale. You should definitely get yourself a good test kit, the Taylor K-2006 you can get at a good online price here or the TF100 test kit from tftestkits(dot)com here with the latter kit having 36% more volume of reagents so is comparably priced "per test". These tests both have a FAS-DPD chlorine test that is accurate to within 0.2 ppm, measures both Free Chlorine (FC) and Combined Chlorine (CC), does not bleach out from high FC (so is useful even during shocking and can measure up to 50 ppm).

You can use The Pool Calculator to enter in your pool water chemistry numbers and see if the Calcite Saturation Index is too high. I suspect that your pH is too high and probably also your Total Alkalinity (TA) and maybe even your Calcium Hardness (CH) as well.

If you do have scale, then getting rid of it isn't easy, but involves lowering your pool's pH for a time and brushing the scale to dissolve it. If it's really bad, then an acid wash may be needed, but hopefully if the scale isn't too thick and is relatively new then acidic conditions (negative CSI) will dissolve it (BUT you have to protect other equipment, especially a gas heater if it has a copper heat exchanger).

Richard