Does pH change when covered/with lack of sunlight?

Hi all,

I'll first apologize because brevity isn't one of my strong points. I covered my pool early this year--a couple of weeks ago--although here in Alabama I'd be covering it about now anyway because with shortening days and cooler nights the water temps become too cold for me. I'd taken a hard spill off my bicycle and cracked a couple of ribs, and although on the 10th day after the fall I went through an amazingly quick recovery I expected it to be much longer and didn't want the burden of maintaining the pool, especially because we were heading into a prolonged rainy period.

It's still been very hot, however, and so I'll typically turn the pump on every day for an hour or two just to keep the chlorine somewhat distributed.

For the heck of it last night I checked my pH in addition to the CL after running the pump. Instead of moving a couple of water bags and taking a sample at the skimmer, I put the multiport to closed and took the sample at the pump basket.

I covered the pool at 5 ppm and with the pH spot on. My CL had dropped to 4.5 over these past two weeks (totally acceptable), and the pH, well, it was an anemic color that didn't match anything on the color-charted pH tube.

My newer liner is only a couple of seasons old, so I have more invested in staying on top of things. I'm hoping that this odd coloration is benign - that it has something to do with the lack of sunlight on the water?

I know a lot of people in the south who are surrounded by lots of trees close their pools during the winter, but I just cover mine and run the pump during the handful of winter nights the temps drop below 28 or so and are sustained. My pump is in a protected lower elevation of the yard, right next to the door to my heated crawl, so I don't worry about any temps between 32 and 28; if a power failure I can open the crawl or run a space heater if need be.

Therefore, I do have the capacity to keep my chem numbers in line. But it just seems really really strange to be adjusting my pH during the long time it's covered when it's covered (9 months because of very messy springtime budding of trees) in order to protect my liner from an inappropriate pH. Those who do close their pools, but whose water doesn't freeze here in the south, don't have the capacity to adjust their pH and you don't hear about liner ruination because of it…?

As I recall, when I uncover my pool June 1st, the pH is an off color as well, but within a couple of days it pinks up all on its own. For my pool--except with the new fill water when I got the new liner--I have to add a bit of acid throughout the summer to keep it in line; the pH is never too low.

So, I look forward to the expert minds *hopefully* telling me I don't have to adjust the pH during the next 9 months (please…). I haven't done so the last two winter seasons and at least don't perceive any liner damage therefrom.

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On another matter, I have a new pool cover this season. 15-year warranty; it's not a cheap cover (although my covers never seem to last more than two or three seasons because of the hordes of debris from trees that fall on them), but experience has taught me that a cheap cover is good for about one week before seams begin to pull apart. I only see one seam, and it's going down the middle, long- to long-end, and it's seeping pool water. Indeed, a paper that arrived with the new cover said "do not pump water off your cover during the fall, leave it on until you reopen the pool as a cover pump will pump water seeping from the seam(s)."

It surprises me that with today's technology some type of adhesive cannot be added to any seam to keep water from seeping, but you'd assume if it were pool cover manufacturers would be using it? It would be ludicrous for me not to pump water off my cover. It would eventually turn into a swamp, and the debris from trees would be so deep I'd have to hire an entire a crew of workers to clean it off in the spring. I brush, rake and blow debris off my cover every week from Fall through Spring. Without keeping the debris off, one can't effectively pump the water off because debris will clog up the screen at the bottom of my Rule automatic pump. And, I would abhor looking at a cluttered, dirty, swampy cover in any case as the pool is only 15 feet from my patio door. So I have moved the pump off the seam (which continues to seep) to the side (I'll have to brush copious amounts of rainwater to the pump) and I guess will just have to add water as needed so I can run the pump during frigid winter nights. At least now I know why in seasons past my water level would curiously drop from time to time. I always worried about liner leaks but it was cover seam seepage. Blows my mind they can't create cover seams that don't seep.

Hi elsie,

It's good to see you back around the forum!! Hope the ribs continue to heal and don't give you any problems--broken ribs HURT!!

I don't have any idea what to tell you about the pool cover. I'm in Lousiana, maintain my pool open year-round, and don't own a pool cover. Hopefully someone who does will be by soon to help with that.

Regarding the pH of the pool, I can't think of a reason why the lack of sunlight on pool water would affect the pH of the water, although chemgeek, waterbear, Ben, or some of the others more "chemistry minded" may come by and know better than I. However, leaves, acorns, etc that get into the pool could affect it, as well as extended rainy periods, and/or whatever method of chorine that you're adding. If it were my pool, especially with the new liner and the ability to do so, I would do whatever necessary to keep the pH in line to prevent liner damage. I know it can be a real pain, but not as big a pain as replacing a new liner would be!!

Janet

Even with the pool covered it's pretty amazing to only drop from 5 ppm FC to 4.5 ppm FC over 2 weeks. That usually only happens when the water is much colder -- is the water cold now?

As for pH, I don't know what you mean by an anemic color. It's the hue that matters in terms of the pH test, not the intensity of the color. So is it yellowish or is it pinkish? As water gets colder, the pH will naturally rise a little bit. When the water warms up, the pH drops back down. Over extended periods of time even with a pool cover one can have some carbon dioxide outgassing making the pH rise.

Anyway, regardless of the source, it seems that one should check their chlorine and pH levels at least once a month even when the water is very cold (when one doesn't close by draining below skimmer and returns for winterizing, etc.).

In my own pool, I found that the pH rose over the winter, but every pool is different.

Hi Janet, thanks! I have 8-ft-long double-tube end-to-end water bags around the pool so not even a piece of pine straw or snail will make its way into the pool until I uncover next June (curiously, snails come from the ground here in central AL, far from the coast--can you tell I'm not a native?)! Virtually nothing has changed since I covered it except lack of sunlight. I sure wish I could keep it open year-round like you do (but then there would also be the expense of running the pump). The trees really preclude that. In my naïveté 8 years ago when I moved from the north and landed here and bought the property I uncovered it Jan. 1st after all the trees were bare, only to experience week after week of trees dropping various things in the spring - I mean, the stuff gets so deep you can almost shovel it. You can imagine what it has the capacity to do to a pool/pump, esp. the impeller.

Chem geek, when I took a test sample last night, the water was still fairly warm - I'd guess 81-82 (although this will change fast now that the nights are cooling off). By "anemic" I mean that there was no intensity of hue - it was weak, or, anemic. If I had to extrapolate at all, I'd say it was low vs. high. There was no pink to it at all. I'll retest tonight and look at it more critically. Still, I don't understand why it would abruptly change since the time it was covered when the pH was stable all season long except for having to add two cups of acid every few weeks. That's why I wondered if sunlight is the change component. Nothing else seems to make any sense. Alas, it was easier these past two seasons just not testing pH as I never worried about it. That said, with pools, ignorance is not bliss.

It sounds like maybe the pH drops you are using are the wrong one for your test kit. The R-0014 drops are for the K-1000 type test kits with the smaller (20 ml ?) viewing tube while the R-0004 drops are for the K-2000 type kits with the larger (44 ml) viewing tube. Either that or the pH indicator dye might be too old.

No, it's the right phenol red - I use the AquaChem OTO kit, buying the Aquachem replacement phenol reds as the tube never needs replacing. It's the same kit I used all summer and when I covered the pool. In fact, for this most recent test I used both an almost-empty phenol red and a new replacement phenol red I had not yet opened, and both times the colors were the same, which is an ever-so-pale orange. Clearly, my pH is not high, it must be low. It's just so pale it doesn't begin to match any of the colors on the tube and frankly I don't know how to extrapolate that reading.

The other night I took a water sample and left it outside in the light and retested at night, and got the same result.

The only variables which changed when I covered the pool 2-1/2 weeks ago and now are:

1. Pump is run only an hour a day vs. 24-7 when pool uncovered;
2. Water is devoid of natural light;
3. New cover; and
4. Water sample taken at pump basket instead of directly from pool.

So, the conundrum continues. I guess I should add some Borax?

By the way, early on in the season I happened to be at an Ace Hardware store and bought their brand OTO kit. When I tested the water after uncovering the pool it was a similar weird color. I remembered this happened once before when I bought another brand OTO from Home Depot. So I went back to the AquaChem sold by Walmart (in both cases), and got the correct pink color. I should've brought Ace's back and told them that their OTO test kit could be ruining a lot of liners because it was so inaccurate. At least that was my conclusion - and a very scarey one at that.

Quote:

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Originally Posted by elsie

So, the conundrum continues. I guess I should add some Borax?

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Yes, you can use 20 Mule Team Borax to raise the pH. If the TA were very low as well, then you could use Arm & Hammer Super Washing Soda (careful: NOT the laundry detergent) instead or some of each depending on how much the TA needs to be raised.