Post tetraborate experiment maintenance

[kelemvor]

A few months ago I did the sodium tetraborate thing, bringing my borates up to 50ppm in an effort to slow pH rise due to my swcg.

I generally drop ph to 7.2 about every two weeks, which is about the time it will be reading 8.0. It seems to have slowed such that it only needs acid every 3 weeks, but unfortunately I haven't been diligent about recording my test results hence the vague estimates.

A few times (particularly while my pool was "closed" for about 6 weeks in jan-feb) have fallen off the wagon on maintaining pH. What I've noticed is that my pH rise always seems to stop right at about 8.0 (based on acid demand test, it's not going much further than the outside edge of the pH test). Since it's back to swim season here in FL, I've been maintaining daily (actually twice daily on many days, due to filter needing to be flushed of pollen).

The borates thing was kind of interesting to me, but I'm starting to wonder about running the pool normally at pH of 8, where it seems to want to be. I've read this http://poolsolutions.com/gd/hiphpool.html numerous times; so I am thinking it probably won't be a problem. Do I need to account for the borate content at this point for any purpose other than stabilizing pH drift?

[chem geek]

The rise in pH will naturally slow down at higher pH as well as at lower TA. This chart can give you a rough idea of how over-carbonated your pool water is with respect to air so you can see that at 8.0 and reasonably low TA the pool is not very over-carbonated.

Anyway, the main problem with higher pH is if your CH and TA are also high enough to cause calcium scaling. This is most problematic with your salt cell since scale will often form there first. At least with the borates, this problem is lessened. The other issue for high pH is the possibility of metal staining. So, as Ben's high pH pool page indicates, it is certainly doable but you have to understand the risks. You can certainly manage the TA and possibly the CH to have the saturation index still be near 0 even at high pH so that just leaves the problem of metal staining which may not be of concern if you don't have metal ions in your water.

The borates only slightly affect the saturation index and if you use The Pool Calculator then that is handled for you automatically.

[waterbear]

My 2 cents about pH with 50 ppm borate and a SWCG. Don't drop the pH to 7.2. In fact, don't drop it lower than 7.6. It will tend to stay right around 7.7 for a long time. When it climbs above 7.8 it's time to drop it back down to 7.6. Make sure you keep your TA at 70 ppm (and bring up the CH if you have a plaster or fiberglass pool to keep the water balanced) and keep the CYA at the manfuacturers recommended max. (usually 80 or 100 ppm).
BTW, even with an acid demand test you really have no way of knowing just how high above 8.0 your pH has risen because the amount of buffer (bicarbonate and borare) in the water will have an effect on the demand tests. All you really know is that the pH is 8.0 or above. If you want to know how much above you would need a different pH indicator solution that tests a higher pH range.