Problem raising pH

[Guest]

I've had a major problem raising pH above 7 for the past year. My pool store says to add soda ash, but no matter how much soda ash i put in, the pH hardly rises at all. Last year i added almost 50 lbs over the course of 2 weeks, and the pH hardly changed! Haven't seen a pH above 7.2 in a year.
i'm using either dichlor granules or trichlor tablets on a daily basis to keep the FC at about 5 ppm. There's no combined chlorine. The Calcium is 105 and the alkalinity is 110. The CYA is 100. pH is 6.7. The water is clear.
Any ideas would be greatly appreciated!
-wayne

 

[ivyleager]

Welcome!

Di-chlor and trichlor pucks drive pH WAY down (and continue to increase CYA). Bleach will not. By continuing to use those chlorination methods, you will continue to be pH challenged.

Soda ash raises pH AND ALK, so using borax would limit ALK increases while raising pH.

Lastly, what testing method are you using?

Hope this helps.

 

[JasonLion]

PH below 7.0 can damage the pool, especially if it remains low for long periods of time.

For every trichlor tablet you use, you need to add somewhere around 4 oz of soda ash. With a pool as large as yours, the total amount of soda ash required will be substantial.

 

[AquaDoctorLLC]

First I'd lower you CYA to around 70. Which means you'll have to do a partial drain on your pool. TA is a fine.

From looking at a Taylor "Testing & Treatment Guide" a 60,000 gallon pool, would take 19.2 lbs of Soda Ash to correct pH at 10 drops. I can guarantee you that 10 drops won't move a 6.7 pH to 7.6. It would more then likely (without being there & testing it) take 30-50 drops. So 50#s of Soda Ash, is not that large of an amount.

Have you tested your source water? I have a pool that the source water TA is 600 out of the tap. So I have to use a HUGE amount of acid in water columns to lower the pH

 

[Guest]

Thanks guys, though i'm still not sure what to do. Here's some more info. I check the chemicals with one of those Taylor kits, sometimes verified by the local pool store, and measure pH with a laboratory pH meter. I know dichlor and trichlor will lower pH, but why don't friends with pools have this same problem? The calculations that come with the soda ash don't require anything close to 50 lbs, so i'm not sure what you meand by "drops". Is draining the only way to neutralize CYA?
And lastly, bleach does sound attractive, i wonder how people deal with so many bottles, and where to buy it in large quantities. And if there's any way to store it like in a big tank. It seems cumbersome. Also doesn't the FC fluctuate a lot between each bleach bolus?

 

[duraleigh]

Thanks guys, though i'm still not sure what to do.

I would get the pH up into the 7's before I gave ANYTHING else a thought. It will take 10+pounds of soda ash but you are not helping yourself leaving your pH below 7.0.

Secondly, I would drain about 50% of the pool to get my CYA to a manageable 50ppm or so. In fact, you could do that first and then refill.....you probably will use far less soda ash.

Last, I would stop using dichlor and trichlor as a source of chlorination since that's what's causing your problems in the first place.

 

[JasonLion]

Thanks guys, though

Raise your PH up to 7.8 right away. Persistently low PH is damaging your pool. I calculate about 32 lbs of soda ash, or 63 lbs of borax, to raise your PH to something more reasonable, and something like 10 oz of soda ash a day if everything is going well, more if you are using any dichlor at all.

AquaDoctorLLC is talking about a base demand test, which measures how much soda ash is required to raise the PH in "drops", which then get looked up in a table based on your pool size.

Others don't report this "problem" because it isn't a problem. If you use trichlor it is just routine to raise the PH back up, hardly worth mentioning.

Yes, replacing water is the only way to get CYA down.

 

[Guest]

Thanks Dave and Site Admin for your comments. It seems there's a lot of misinformation out there about pools, and i appreciate your comments. My local pool store that installed our liner has acceptable CYA level between 30 and 200. But perhaps the problem i've had with the dreaded pink mold is related to not enough FC with all the CYA.

But it's not clear why the low pH is so bad. 7.0 is neutral and except for a few stainless screw heads, i've got no metal anywhere. But since you guys seem to know what you are talking about, i'll give it another try and put in the 35 lbs of soda ash. Based on last year, however, i'd be surprised if it raised the pH more than 0.4. I'll report back in a few days or so on this.

Dave, you have a pool the size of mine, and i wonder approximately how much bleach you use per month, and how often you add it.

I've been thinking of a new salt generator, since my pool guy says they've been improved. I had one about 6-8 years ago, but it was inadequate for the size of my pool (so FC could never get above 3) and the elements frequently corroded, so every 3 years it was another $800 to replace. Then i went to the Polaris automatic Dichlor feeder (with ORP sensor), but without a stable pH this stopped regulating after 2 years. Now i'm where i am with adding triclor or dichlor, but would like to do better.

 

[chem geek]

7.0 is neutral and except for a few stainless screw heads, i've got no metal anywhere.

"neutral" does not mean "not corrosive to metal". Most water districts raise the pH of their water to the 7.7 to 8.0 range in order to reduce the rate of metal corrosion.

 

[JasonLion]

If the PH is 7.0, it isn't so bad. Most people get some eye irritation when the PH is below 7.2, so 7.0 isn't ideal, but still not a serious problem.

The more problems come when the PH is below 7.0, for example you originally posted that your PH was 6.7. PH below 7.0 will shorten the lifetime of the liner, the further below 7.0, and the longer the PH remains low, the more dramatic this effect, so that a few days at 6.9 is not a big deal at all, but a few months at 6.0 can be a serious problem.

The cell of a SWG will wear out and need to be replaced. This happens much more quickly when the cell is undersized for the pool. Even taking that into account, a SWG usually ends up being about the same cost in the long run. The weekly savings in chlorine, that you would otherwise have to add, eventually paying back the initial costs.