Autopilot SWG, Ph and TA

I have been struggling to get a mustard algae bloom under control, but everything seems okay now. Thank you to many on the forum who helped with their sage advice.

Now on to the next issue of importance - high Ph, SWG and plummeting TA. For reference, I have a 22,500 IG plaster/guinte pool with autopilot SWG with the 40k gallon rated cell.

1. To maintain my Ph around 7.4 to 7.6, I am having to add at least a pint of muriatic acid a day, sometimes more. It has been that way since we opened the pool last september. I know and understand that an SWG tends to cause the Ph to rise. I have also heard that plaster can cause a greater acid demand.

But it just seems like there is a HUGE demand. Maybe adding a pint a day isn't a big deal. So just looking for someone to make me feel better :D about it, or let me know something else might be going on :eek: .

2. As well, the TA crawls down, and I have been adding a 4 lb box of Baking Soda about every 2 weeks or so when it gets down to 80, which then causes it to go back up to 110-120 range. Again, don't mind doing this, but just seems like a high frequency of adding Baking Soda?

3. A little off subject, but I noted that the autopilot manual says that desireable CYA is 60-80. This seems high. Is it? I would rather have it lower and not have to have to maintain the higher levels of Ch to maintain proper sanitization, much less the higher levels for superchlorination. Anyone have any thoughts on this? Admittedly, I am relying on my local pool store for my CYA level of 40 (see below).

For reference, here are my most recent drop test kit results:

FC - about 5ppm (my kit stops at 3ppm, this is best guess using CarlD's advice and diluting with distilled water)...on it's way down to 3 or so from superchlorinating with bleach
CC - not measurable
FC - about 5ppm (see FC above)
TA - 110 (added 4 lb box of baking soda 2 days ago, it was 80 before adding)
CYA - don't know...waiting for Ben's kit to arrive. about 3 or 4 weeks ago, pool store said 40
Salt - about 3 or 4 weeks ago, pool store said 2700.
Cal - don't know...waiting Ben's kit to arrive.

Any help, as always, is greatly appreciated.

Quote:

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Originally Posted by SoCalBoo

I have been struggling to get a mustard algae bloom under control, but everything seems okay now. Thank you to many on the forum who helped with their sage advice.

Now on to the next issue of importance - high Ph, SWG and plummeting TA. For reference, I have a 22,500 IG plaster/guinte pool with autopilot SWG with the 40k gallon rated cell.

1. To maintain my Ph around 7.4 to 7.6, I am having to add at least a pint of muriatic acid a day, sometimes more. It has been that way since we opened the pool last september. I know and understand that an SWG tends to cause the Ph to rise. I have also heard that plaster can cause a greater acid demand.

But it just seems like there is a HUGE demand. Maybe adding a pint a day isn't a big deal. So just looking for someone to make me feel better :D about it, or let me know something else might be going on :eek: .

Yes, the plaster can cause a big demand, especially if it is still new. As you are trying to remove the mustard algae, it might be more helpful to use bleach to reduce the load on the SWC.

2. As well, the TA crawls down, and I have been adding a 4 lb box of Baking Soda about every 2 weeks or so when it gets down to 80, which then causes it to go back up to 110-120 range. Again, don't mind doing this, but just seems like a high frequency of adding Baking Soda?

Is there a possiblilty you might be aerating inadvertently, like a waterfall, spa, or having the return jets pointed up too high? Any of these factors including high acid demand can take the TA down.

3. A little off subject, but I noted that the autopilot manual says that desireable CYA is 60-80. This seems high. Is it? I would rather have it lower and not have to have to maintain the higher levels of Ch to maintain proper sanitization, much less the higher levels for superchlorination. Anyone have any thoughts on this? Admittedly, I am relying on my local pool store for my CYA level of 40 (see below).

Once you get your testkit you should be able to get a better idea of what the CYA is. With the Poolpilot DIG220, a level of 50 ppm CYA works fine for us on much the same size/type pool. Running 60-80 ppm means a higher Cl level which from your numbers appears to be what you are running at.

For reference, here are my most recent drop test kit results:

FC - about 5ppm (my kit stops at 3ppm, this is best guess using CarlD's advice and diluting with distilled water)...on it's way down to 3 or so from superchlorinating with bleach
CC - not measurable
FC - about 5ppm (see FC above)
TA - 110 (added 4 lb box of baking soda 2 days ago, it was 80 before adding)
CYA - don't know...waiting for Ben's kit to arrive. about 3 or 4 weeks ago, pool store said 40
Salt - about 3 or 4 weeks ago, pool store said 2700.
Cal - don't know...waiting Ben's kit to arrive.

Any help, as always, is greatly appreciated.

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Hope this helps.

Pat

Thanks Pat. A few follow ups/responses to your queries.

1. During the superchlorination, I unplugged the SWG and used bleach. When I started to read levels approaching 5ppm, I plugged it back in. Reading Ben's best guess chart on CYA, 5ppm seemed to be a good target not knowing what my CYA was accurately. Seems like 5ppm will be decent for CYA levels from 10 to 90 (i.e. within min/max range for those CYA levels).

I plugged cell back in a few days back when TC seemed to be around 6ppm. I has dropped a little to 5 or so (again, these are kind of rough numbers using approximation through dilution). But I think we are pretty close on the level out of the cell for now. It is at level 2, 50%...seems to shift between 50 to 70%. I also need Ben's test for salt calibration, but whatever it is at, it seems like I am close to getting the near optimal output level.

2. I am diluting the acid in a 1 1/2 qt container with water, and then broadcasting over the deep end to try and avoid aeration. I have two very active returns in the shallow end (one pointing somewhat upwards) and then another in the deep, but it is pretty deep and doesn't seem to be affecting the surface in any way. I do have a spa with a spillover. Any advice to avoid any inadvertant aeration? Put the return valve fully to the pool with nothing going to the spa (seems to create a problem of lack of circulation/chlorination to the spa)?

3. Thanks for the advice on CYA. As I said, once I get Ben's kit, I can get a better idea of where I stand. Anyone have a recent delivery that can tell me their waiting time?

I have had exactly this situation going on with my pool since July of 2004. In my case I blame it on my Lowzone systems having an excessive airflow rate resulting in continuous aeration. I recently choked it way back so the I get much less "champagne bubbles" in the pool. I figure the UV bulb can't be producing that much ozone, so excess airflow is just diluting the what ozone is being produced and making it less effective. I know this site is not real keen on lowzone systems to begin with, so I'll leave it at that.