New to the forum, OLD pool, TONS of trouble this year....

[BrianL]

I have a 35K gal inground pool, gunite, circa 1971. Pretty rough shape; some leaks in plumbing below the sidewalk, rough walls, some prior layers of paint showing through.

Been running this pool for about 12 years, usually fairly successfully, using 3" tabs in auto chlorinator. Most years, it's worked really well; in a good year the pool stays usable with minimal weekly work (fill chlorinator, dump in soda ash and a small "preventative" dose of algaecide, auto cleaner often, very occasional brushing).

I do ROUTINELY have a problem getting pH UP; it continually goes down rather rapidly. Reasons:
a) Acidic 3" tabs...about 10/week.
b) Presumably acidic rainfall
c) I mentioned leaks; up to about 2"/week replace with acid well water.

Still, for YEARS, I dumped in about 3-4 cups of soda ash/week and moved on.

NOT SO EASY THIS YEAR.

Algae, along with a pink algaelike bacterial infection, have taken hold and WILL NOT give up.

And I absolutely cannot get PH up above about 7.2. If TA is above about 150, soda ash will not dissolve; it just eventually, slowy, gets filtered out. Water is cloudy for days. If I've added muriatic acid recently (tried more than once!!), then soda ash dissoves readily....until TA goes up again.

History this year:
Pool store ID'd excessive (about 170) TA, had me do acid slug & try to recover. No real progress...surprise.
ID'd "high" phosphates (500); added PhosFree to clear.
In attempts to deal with high TA/constant low PH, I've discontinued using 3" pucks and been using calcium hypochlorite.
Even recently dumped 1/3 of the pool and refilled; after that AND 2gal muriatic acid, got TA down to about 90. But of course pH was way low, and by the time I got it up, TA was back up to 160.....
Elevated chlorine to something astronomical for a few days, and scrubbed the daylights out of the walls; pink and green stuff SEEMED at bay. Until this a.m., first time free chlorine dipped below about 5.0. IT'S BAAAACK.....

Found this site a few days ago, started playing with attempts to aerate. Couldn't successfully use existing outlets & PVC (ancient, nonstandard threads in the outlets; I've never found outlet jets to replace the long-gone originals.) Set up a submersible pump (normally used in winter on my pool cover) and a hose nozzle - spray going about 25' across the pool. That should aerate if anything short of a compressor will...I'll see in the next day or two.

Current stats:

a) FC down to about 2.0 this a.m.; added 3 cups Calcium Hypochlorite at 7am. This evening at 6pm, FC was about 9.5 per a newly acquired Taylor test aimed at high/low range chlorine testing. (Yes, I'm considering the kit sold thru this site...)
b) pH, after 8 hrs. aeration, is up to about 7.5 for the first time this year. Was shooting for 7.8--8.0 to try the "yellow out" sold by the store.
c) TA about 160
d) Cyanuric acid about 60.
e) Don't have a recent test on calcium hardness, but the well water is extremely soft and usually this runs low if anything. Was 180 ppm early this year per pool store test.

Questions:

1) How do I get pH UP and TA DOWN in this pool??
2) Should I be thinking borax? I do have a dog that swims/tends to drink from the pool. But she's about 75 pounds, and USUALLY bites more than drinks.
3) CYA is at 60. AFTER dumping 1/3 water. I'm thinking this is why algae got out of hand, as this site suggests astronomical levels of chlorine are needed at that level of CYA?
4) At 11.5% of CYA, that suggests an ideal FC level of about 7. Resources I have say don't swim above 5. Comments?? How high is too high to swim?
5) Any other suggestions, short of a LONG LINE of dump trucks to fill this thing in???

Thanks!

 

[MikeInTN]

Questions:

1) How do I get pH UP and TA DOWN in this pool??

The only way to permanently lower TA is to add acid to lower your pH to 7.2 or thereabouts if it's not there already, and then start aerating the pool. Lowering the pH causes more of the carbonates that comprise your TA reading to convert to C02; aerating the pool helps the water outgas this CO2 to the atmosphere, and also causes the pH to start rising. Keep repeating this cycle of lowering your pH and then aerating until your TA is where you want it. Then aerate until your pH is where you want it, and then stop aerating, and see if your pH stabilizes. You may have to adjust your TA a bit to stabilize your pH, or at least I did.

2) Should I be thinking borax? I do have a dog that swims/tends to drink from the pool. But she's about 75 pounds, and USUALLY bites more than drinks.

You may want to try raising your borates after you get your TA/pH balanced. Adding borates to the water does have several beneficial effects on the water. My own opinion, my dog's health is more important to me than the benefits I would get from the borates, so even though the general consensus is that the pooch would have to drink lots of pool water to be affected, it's not worth it to me. To each his own, though.

3) CYA is at 60. AFTER dumping 1/3 water. I'm thinking this is why algae got out of hand, as this site suggests astronomical levels of chlorine are needed at that level of CYA?

Very possible, and most likely, due to the need for high levels of FC as you've already pointed out.

4) At 11.5% of CYA, that suggests an ideal FC level of about 7. Resources I have say don't swim above 5. Comments?? How high is too high to swim?

Again, my own personal opinion, but I wouldn't have any problems at all with swimming in a pool w/ a FC of 10 ppm.
Remember that part of the FC combines with the CYA, so only a percentage is available in the water for sanitation, not the full FC that you read with your test kit. That's why higher FC is required for higher levels of CYA to maintain the necessary sanitation level.

5) Any other suggestions, short of a LONG LINE of dump trucks to fill this thing in???

Thanks!

 

[BrianL]

Morning update

This a.m., pH still about 7.5, free chlorine down to 8.0.

Added 1c cal hypo, 2c soda ash; we'll see if it dissolves.

Unless better ideas come along, I'm going to keep trying to push pH up, possibly dump some water again this weekend, evenutally use that yellow-out. Believe I'll take one suggestion from the store and tear down the (old stype Hayward perflex bump DE) filter tomorrow a.m. and clean things w/ bleach. And set the 15 year old to brushing/scrubbing....

Thoughts on Borax? Will it dissolve in this soup? Just how concerned should I be about the dog?

thanks,
b

 

[BrianL]

Morning update, cont.)

(I was really disappointed that pH wasn't higher after my pump "aerator" running all night....)

 

[JasonLion]

Stay away from Yellow-Out. It contains bromine compounds which will just make things much more complicated right now. It can be handy in a few specialized situations, but not this one.

Absolutely try borax. I'm fairly sure it will disolve.

To aerate you want as much disruption of the surface of the water as possible. Is there any way to add a spray head to the spare pump's output?

 

[crokett]

4) At 11.5% of CYA, that suggests an ideal FC level of about 7. Resources I have say don't swim above 5. Comments?? How high is too high to swim?


Thanks!

My FC level is at held at 7 and we swim with no problems. I had some awful algae problems in a new pool this summer and never want that to happen again.

For the aeration, I was thinking maybe a sump pump with some sort of spray head attached. Even a small pump will move around 1800 GPH.

 

[chem geek]

Re: Morning update, cont.)

(I was really disappointed that pH wasn't higher after my pump "aerator" running all night....)

The aeration needs to be done at low pH or else it's not as effective. It sounded like the pH was at 7.5 when the aeration started. See this chart which shows the relative carbon dioxide outgassing rate as a function of TA and pH and notice how much higher this rate is at lower pH. The absolute rate is dependent on aeration, but I can't show that in the chart (not easy to measure or define, etc.).

 

[JohnT]

Re: Morning update

This a.m., pH still about 7.5, free chlorine down to 8.0.

Added 1c cal hypo, 2c soda ash; we'll see if it dissolves.

Unless better ideas come along, I'm going to keep trying to push pH up, possibly dump some water again this weekend, evenutally use that yellow-out. Believe I'll take one suggestion from the store and tear down the (old stype Hayward perflex bump DE) filter tomorrow a.m. and clean things w/ bleach. And set the 15 year old to brushing/scrubbing....

Thoughts on Borax? Will it dissolve in this soup? Just how concerned should I be about the dog?

thanks,
b

A pH of 7.5 is already perfect. No way do you want to raise it. If you want to lower your TA, you'll need the pH down around 7.0 when you aerate.