PH Keeps Dropping

Newbie here. Does Ph ever stabilize? I have read about people with an SWG having trouble maintaining a consistent Ph, but what about those that do not have a SWG. I have a 20,000 gallon inground pool with a vinyl liner. My numbers are:

CYA - 45
TA - 90
CH - 120?
TC - 6.5
CC - 0
Ph - 7.4

I try to keep my clorine levels between 3-6 and I have to add about one 1.4Gallon jug every other day to do that. However, I am just curious if I should also be seeing my Ph drop on a regular basis. It seems like it drops about 0.4 every two weeks. I add Borax to get it back up, but I am just curious if that is normal.

Thanks.

Ph can fluctuate some. Are you using anything other than bleach to chlorinate with? Trichlor and Dichlor are quite acidic. Also, acid rain can lower ph. Any time we get a substantial amount of rain, I find my ph has dropped a little. You may want to bump your TA up just a bit - maybe to 100 - and see if that helps your ph to be more stable.

This is the first year of pool ownership. The previous owners used pucks and furtunately I found this forum before I started tackling this pool. I started with a good test kit and found out, as suspected, that the CYA was off the charts.
After several partial drains and fills I got that under control. I would agree that the rain probably has some to do with my ph dropping. But in the past three days it seems to have gone from 7.6 to 7.3 without any rain. Still puzzling me. Oh well, could be worse. Off to the store to buy more Borax.

Oh by the way, it it OK to just sprinkle the Borax on the surface or should I be trying to disolve in a bucket first?

Thanks.

Hi :)

One reason why your Ph is drifting around could be due to your low TA. Your TA will give you an idea of how easy (or difficult) it will be to change your Ph. The lower the TA...the easier the Ph will react and change. The higher the Ph...the more difficult your Ph will be to change. Just by raising your TA...you may find that your ph drifting problems are gone.

But let's wait for one of the regulars before you go adding anything to your water :)

What kind of a pool? Do you have a heater?

happy swimming!
dan

I have a 16x32 inground pool, with vinyl liner.

Since the two responses I have both indicate that a slightly higher TA might help. I think I will try and bump that a little bit.

Thanks.

Anyone else have any theories as to why my Ph keeps dropping. I know most people have the opposite problem (maybe I should get a SWG ;) )

I have been seeing my Ph drop 0.3 every couple of days. And though rain does seem to play a factor, this seems to happen even when it hasn't rained in quite a long time.

I still plan on raising up my TA a little more, to say 110 or so to see if that will help but just keep forgetting to get some Baking Soda from the store.

Thanks,

Riles

Riles,

Your dropping pH is truly a mystery and it is true that in your case (and only in cases like yours where the pH is dropping consistently) a higher TA will help for multiple reasons. It will not only increase the buffering of the pH, but even more importantly it will increase the amount of outgassing of carbon dioxide which will make the pH rise. However, if you could hold off on raising the TA a few days until we figure out the mystery, that would be helpful because if we find the source we can turn it off and see if that helps. Otherwise, if you increase the TA to compensate it will be harder to isolate the source of the dropping pH (but it's up to you and I'll understand completely if you've just had it and want to fix the problem immediately).

I'm going to ask you some questions to see if we can figure out this mysterious source of dropping pH since it truly is quite strange given your source of chlorine.

Do you use a pool cover and if so, how often is it on?
Do you have any sources of aeration (waterfall, spillover, fountain, air jets, etc.)? I suspect not, given the pH dropping.
What other chemicals are you adding to the pool regularly (even weekly or bi-weekly) other than bleach (or chlorinating liquid) and Borax? Are you adding a non-chlorine shock (potassium monopersulfate) on a regular basis? Are you adding PolyQuat 60 or any other algaecide?
Do you have anything falling into your pool such as leaves or debris of any kind? If so, what is it that falls in?
Is there any runoff from nearby soil or is there liquid of any kind finding its way into your pool (other than what you explicitly add)?
Is there sunlight that shines on your pool?

As for your question about how to distribute Borax, I would just slowly pour it over a return in the deep end of the pool, but take a look and see if it seems to fully dissolve and not accumulate on the bottom at all. If it appears to be slow to dissolve, then I would mix it in a bucket first and then slowly pour that over the return instead. Try to pour away from the wall, if possible. These extra precautions are mostly due to your vinyl pool, though I doubt that the Borax will be a problem (it's not acidic and not chlorine -- those are probably bigger issues for vinyl pools).

Richard

Richard,

I would be happy to try an figure this out because it has been puzzling me as well.

Answers:

1) There was a solid pool cover put on this winter by the previous owners. I took it off in December and there has been no cover on it since. I do not own a solar cover.

2) I don't really have any sources of aeration. Just two returns, although I have been getting some air in my system that I haven't tracked down yet as I get small bubbles every so often that come out my returns. I think it is from a bad seal on the pump basket.

3) No other chemicals are added except bleach and borax.

4) I do have quite a bit of leaves that have been falling in the pool. Had that under control until we got a late freeze in April and all the leaves of the surrounding trees died. It was like fall all over again :mad:. I also get a fair amount of pollen. Another thing I have been finding is that the pool is dirty with silt a day or two after vacuuming. I assume it is from the silt just getting stirred up when I vacuum and then settling back out. I have been meaning to test to see if I am getting any blow by from my filter. Other than that I get a few worms and salamanders on occassion.

5) No runoff from nearby soil or other liquid is finding it's way in that I know about.

6) The pool gets quite a bit of direct sunshine through most of the day.


Hopefully I answered all your questions. I will hold off on adding any baking soda to see if there is some other reason for the dropping Ph.

Thanks,

Riles

Riles,

Try this. Take a large bucket of pool water and place it near the pool, but cover it with a cloth. See if the pH drops in the bucket as quickly as it does in the pool. If it doesn't, then perhaps the leaves or pollen or other junk getting into the pool is acidic. That's my best guess at this point. Perhaps someone else has an idea as well.

[EDIT] A better idea would be to have TWO buckets of pool water -- one without the leaves and pollen and the other with leaves and pollen. Measure the pH of each (they should be about the same), then cover them both so they don't get more stuff in them, then see if the pH changes differently in the two.

If the problem ends up being the leaves and pollen, then raising the TA would be a solution, but you may need to lower it again when the leaves and pollen stop dropping. I'll be surprised if the leaves and pollen are causing this, but I don't have any other answer for it.[END-EDIT]

Richard

Have you tested the pH of your fill water?

Janet

I have not tested our fill, but we have not put much fill water in the pool yet this year. I can run that just to find out though.

I have no idea what was used to chlorinate up until I took ownership in October of last year. Could that have any impact? Some sort of residual from an acidic-type chorinating left over? Seems highly unlikely, but I'm reaching.

What sort of normal drop in Ph should I expect? Let's assume there is no rain or chemicals (aside from bleach) being added? It seems like it should remain relatively constant if no acid is being added.

I'll keep you posted.

Riles