Borates, good TA, pH still goes high

[wes8398]

I have about 30 ppm borates and a solid TA of about 80, but my pH keeps floating up. What gives? Is it usual to have to add dry acid every couple days?? A few nights ago I brought pH down to 7.4 or so, but now it's back up to 8-8.2 already. I've been using MPS to oxidize my bromine, which I thought would lower pH and TA, but doesn't seem to be doing so. I'm also using bromine pucks in a small floater with just one notch open.

Any ideas?

 

[anonapersona]

My pH is not stable at TA 80 either, but at 60 it is.

 

[zea3]

Do you have any water features such as waterfalls, fountains, jets, ect? Does the surface of the water ripple when the pump is running?

 

[JasonLion]

anonapersona has the right idea, let TA come down some more.

 

[wes8398]

Hmmm, ok. I'll bring TA down some which will be easy since I need to bring pH down too.

As for 'features', it's got 90-some jets, half powered by a high/low/off pump, and the other half powered by an on/off pump. Most if not all the jets have valves to allow air injection into the water output. There are also 2 'stream' waterfalls and then a more conventional wide waterfall. We have them dialed down though and they don't disturb the water much at all. When the low (circulation) pump runs, the water's surface ripples but isn't bubbling or anything like that, and the water features barely dribble out.

 

[anonapersona]

The waterfall and streams will count as aeration anytime they run, a far as TA and pH go. But you can aerate the pool like crazy with all that stuff turned on. Lowering the TA ought to be a snap.

 

[wes8398]

Well I've been playing this stupid pH game for the last few days, even after I brought my TA down to ~50 or 60. For the last 3 mornings I've used dry acid to bring the pH down to 7.2 (and once down to less than 6.8). After that I'd make sure my TA was good(and adjust if necessary), then I'd leave the tub to do it's thing. In the evening I'd check again and pH would be up in the 7.8-8.0 range again! Uuuugh!!!
Last night I thought of something. We've always left the Venturi air valves open, even when not using the tub. That means that for the two daily 2 hour cleaning intervals as well as the once or twice an hour that it kicks on for a minute or two, air has been being injected into the jet's output. Could this be the cause of the pH rise? Do spa owners usually need to close these valves when not using the tub? Or is something still amiss that needs to be corrected?

 

[chem geek]

You can certainly try turning off the air valves and see what happens. Also note that the rate of pH rise slows down as the pH gets higher so it might settle in closer to 7.7 or 7.8, but let us know what happens if you turn off those air valves.

 

[wes8398]

Well after some time with barely using the tub and checking water daily, even with the Venturi air turned off for filtration cycles, the pH still creeps up very high after a few days. I would use 6 teaspoons of dry acid to get it back down to a reasonable level, and then it would come back up again. According to the pool calculator the dry acid i was adding shouldn't have affected my TA too much, but it's down from around 60 to 25 now, after about 2 dry acid treatments. Funny thing is, now that the TA is down this low, the pH just might be stabilizing!! If that's the case and my pH stays down, is a TA of 25 ok?

 

[JasonLion]

TA at 25 is very low. Having borates helps, but there might still be problems with the PH swinging around when you add chemicals.

 

[wes8398]

For 3 days or so I haven't bothered to bring TA back up, yet every day I test pH and it's staying pretty stable around 7.4. Maybe it's coincidence, but whenever I've had higher TA, it only takes a few days for my pH test to go from 7.2 to 8.2+. This is the longest it's gone with a reasonable pH... I know 25 TA is pretty low but maybe, for some reason, that's my water's happy place...?

 

[dmanb2b]

How are you testing TA? Strip or drop based Kit? A result of 25 seems odd, since the drop based kit measures in increments of 10.

 

[wes8398]

TF100 drop test. I say 25 because the 2nd drop made it a greeny-red and the third drop made it the pink-red that we look for.... So I call that in between...25.

 

[Bama Rambler]

The proper way to do the drop test is to drop R-0009 until the sample stops turning and then don't count the drop that didn't make a change. I suspect your TA is higher than you think it is.

 

[wes8398]

The proper way to do the drop test is to drop R-0009 until the sample stops turning and then don't count the drop that didn't make a change. I suspect your TA is higher than you think it is.

Hmmm, apparently I've overlooked that detail for the last 2 years! So let the sample continue turning different shades of pink/red and count those drops until it doesn't change anymore. I wonder why the TF kit instructions say to add drops just until sample turns pink...?

 

[wes8398]

Retested water tonight, following the suggested procedures for TA. TA was 30, no doubt. pH was still stable at about 7.5 and TB (bromine) was at 2. I added a bit of bleach and called it a day... Such a low TA does have me concerned, but this is the most stable my pH has been...