Water Balancing Issues On A Refill

[njmurvin]

I have a Marquis Everyday 660 with stated capacity of 390 gal. So, I figure it has about 350 gal in it. I use the 3 step bromine system and I use the Taylor 2106 kit. After the fill, my TA was about 60 and my pH was 8. By the time I got the spa drained and filled, the pool stores were closed and Home Depot/Lowes did not have dry acid. So, I borrowed a gal of my neighbor's Muriatic acid to lower my pH. I added about 1oz of acid last night and it knocked down the pH to about 7.2. This morning it was back up near 8. I put another 1/2oz of acid in and left for work. I measured again when I got home and it was back up around 7.8. I tested the TA again and it is now around 40. I guess the acid is lowering the TA. I hit it again with another 1/2oz of acid and the pH is back down to 7.2. I will measure all again in the morning.

Also, I added a 2oz (wt) packet of Leisure Time sodium bromide (99%) to establish the bromide bank. I ran the jets for about 15 min before shocking with 6oz (volume) of 6% bleach. Maybe I added the bleach too soon because the bromine didn't spike as expected (7.5). This was all done last night. I put the floater back in and shut the cover for the night. Tonight the bromine measured about 6.25. I didn't measure the CH yet. I don't know how to run the jets without the heater. So it is now up to temp (I have it set to 98F).

Should I raise the TA with baking soda? It was at 40 before the last dose of acid. If I do, I'm afraid the pH will run up again.

Should I shock again to super-brominate the new water?

If the CH is out of whack, could that explain any of this?

Any other recommendations?

[chem geek]

I wouldn't raise the TA very much, especially if you find that the pH tends to rise. The bromine tabs should help keep the pH down, but the general rule is that if the pH tends to rise, then do NOT raise the TA, but perhaps even lower it. So see what happens if you keep it at 40 ppm for now. If the pH is fairly stable, then great. If it tends to drop or if the TA keeps getting lower, then you can increase it, but probably not above 50-60 ppm. The CH should not have any effect on the pH or TA. As for super-brominating, that shouldn't be necessary with a fresh water fill assuming you are filling with clean water.

[njmurvin]

I wouldn't raise the TA very much, especially if you find that the pH tends to rise. The bromine tabs should help keep the pH down, but the general rule is that if the pH tends to rise, then do NOT raise the TA, but perhaps even lower it. So see what happens if you keep it at 40 ppm for now. If the pH is fairly stable, then great. If it tends to drop or if the TA keeps getting lower, then you can increase it, but probably not above 50-60 ppm. The CH should not have any effect on the pH or TA. As for super-brominating, that shouldn't be necessary with a fresh water fill assuming you are filling with clean water.

Just curious .... why does the "Bromine for Beginners" instruct you to adjust the TA to 100?

[chem geek]

Because normally when using bromine tabs they are net acidic so a higher TA would normally be appropriate. However, the actual TA level where pH would be stable depends on the amount of aeration/outgassing in the spa. Since you are reporting a tendency for the pH to rise, you want to keep your TA lower so it doesn't contribute too much to that pH rise (from carbon dioxide outgassing). If you find that when using the bromine tabs, that the pH tends to drop over time, then you can raise your TA level -- even above 60 ppm if the pH still tends to drop at that TA level (I just figured it wouldn't since it's rising now with the TA at 40 ppm). At some point, you should find a TA level where the pH is reasonably stable. The bromine tabs will slowly lower the TA over time so you'll add baking soda every now and then, but the pH should be more stable because the net acidity from bromine tab usage will balance out the carbon dioxide outgassing from the higher TA.

It's always very hard to have a single TA recommendation, but one has to choose something for a "recommendation" post. Perhaps 80 ppm might be more appropriate for the bromine spa beginner post, but it really depends on how much aeration there is or how often the spa is used (i.e. cover off).

pH balance is literally like a balance scale or see-saw with different factors affecting pH. I'll try and draw it as follows:

MPS . Trichlor . Bromine Tabs . Dichlor ................. High TA / Aeration

_______________________________________________________

..................................................................... A .....................................

Lower pH ............................................................................. Higher pH

[njmurvin]

Because normally when using bromine tabs they are net acidic so a higher TA would normally be appropriate. However, the actual TA level where pH would be stable depends on the amount of aeration/outgassing in the spa. Since you are reporting a tendency for the pH to rise, you want to keep your TA lower so it doesn't contribute too much to that pH rise (from carbon dioxide outgassing). If you find that when using the bromine tabs, that the pH tends to drop over time, then you can raise your TA level -- even above 60 ppm if the pH still tends to drop at that TA level (I just figured it wouldn't since it's rising now with the TA at 40 ppm). At some point, you should find a TA level where the pH is reasonably stable. The bromine tabs will slowly lower the TA over time so you'll add baking soda every now and then, but the pH should be more stable because the net acidity from bromine tab usage will balance out the carbon dioxide outgassing from the higher TA.

It's always very hard to have a single TA recommendation, but one has to choose something for a "recommendation" post. Perhaps 80 ppm might be more appropriate for the bromine spa beginner post, but it really depends on how much aeration there is or how often the spa is used (i.e. cover off).

pH balance is literally like a balance scale or see-saw with different factors affecting pH. I'll try and draw it as follows:

MPS . Trichlor . Bromine Tabs . Dichlor ................. High TA / Aeration

_______________________________________________________

..................................................................... A .....................................

Lower pH ............................................................................. Higher pH

Thanks! I think I get the picture. No absolute for TA, just find what makes the pH stable. My spa gets little use so the cover is on 99.9% and little aeration. pH was pretty stable (occasional pH UP needed due to the bromine tabs - maybe once a month) before the water change. I didn't really monitor the TA closely. I will check it more often now just to see the level I need to use as a target.

Thanks for all your input. It's greatly appreciated.

[chem geek]

It sounds like your TA level before the water change was close to where it should be since the pH was fairly stable or only slowly dropping -- what was that TA level? When the cover is on almost all the time because the spa is not used very much (say once a month or less), then the TA level will have less of an effect in terms of having the pH rise or counteracting a drop in pH directly. However, higher TA does buffer pH so that the drop in pH from the bromine tabs will be smaller. Since the bromine tabs will slowly lower the TA over time, unless you check on the spa at least once a week, you'll probably be better off with the TA higher and more like the 100 ppm recommended in the beginner's guide. As you say, this is really something you need to dial in yourself based on your spa's specific usage.

I suspect that perhaps after this new fill the reason you saw more pH rise was that you were adjusting the water chemistry having the cover off and having more aeration from circulation and jets running since you were adding chemicals and mixing them and you didn't initially have the bromine tabs in. Once the bromine tabs are in a steady-state of dissolving and the cover is on more consistently, you'll probably be back to the situation you had before the water change, assuming your usage pattern was similarly infrequent.

[waterbear]

Also, you indicated that on this fill you added bromine starter (99% sodium bromide?) and tabs in the floater, but didn't mention shocking to activate the sanitizer? .

Yes he did.

Also, I added a 2oz (wt) packet of Leisure Time sodium bromide (99%) to establish the bromide bank. I ran the jets for about 15 min before shocking with 6oz (volume) of 6% bleach.

[waterbear]

The CH should not have any effect on the pH or TA

Not directly BUT if the pH is high, the TA is high, and the CH is high you can precipitate calcium carbonate, which would cause a drop in both TA and CH

[jeffinpickering]

Also, you indicated that on this fill you added bromine starter (99% sodium bromide?) and tabs in the floater, but didn't mention shocking to activate the sanitizer? .

Yes he did.

Also, I added a 2oz (wt) packet of Leisure Time sodium bromide (99%) to establish the bromide bank. I ran the jets for about 15 min before shocking with 6oz (volume) of 6% bleach.

He mentioned doing it the first time around, but not the second. Where did the subsequent post go where he said he drained and filled again and still ended up with cloudy water because of residual in the plumbing? That's where he mentioned adding bromine starter, and putting the floater in, but nothing about shocking to activate the sanitizer. I also suggested he vacuum/blow out with a shopvac when draining and filling.