Gunite, SWCG, Infinity edge pool Owners experience

[Flavius]

I had a liner pool for several years. Chemistry control seemed easy.

I now have a gunite pool with pebble finish, SWCG and infinity edge with bubblers. The pool is 31,000 gallons. I use a full taylor test kit.

We only run the bubblers when needed to reduce aeration.
We only run the infinity edge enough to keep the chemistry up with the pool AND when swimmers are present to keep from overflowing.

Here are the things I am curious about and am wondering what others are seeing:
1. I was told I would be putting acid in the pool forever. So far that seems to be the case. (~10 oz every other day in the summer) I have given up on achieving 7.5 and look more at 7.7 as a sustainable target. This could play into #3 below.
2. I seem to need to regularly add calcium to keep that up (~4x per year). I adjusted it to 250 about 60 days ago and now it is at 200.
3. I seem to have to add baking soda regularly to keep the alkalinity up. I adjusted it to 100 sixty days ago and now it is below 50.

We have had about 9" of rain in the last two months.

I have not added a lot of other details here that may be necessary in order to keep this post short.

Do others with a similar pool set up see similar things? IF so what are your solutions? It may be that I just have to test often and make adjustments more often. I generally test pH and Cl every other day or so. But sometimes I just pour a bit of acid in the pool and call it good.

 

[Katodude]

Sounds like you are trying to chase numbers. Look at your CSI and keep it slightly negative. With the TA and CH level you are mentioning you can keep your pH at 7.9 without problems (in fact you probably need to).

 

[Bperry]

I had a liner pool for several years. Chemistry control seemed easy.

I now have a gunite pool with pebble finish, SWCG and infinity edge with bubblers. The pool is 31,000 gallons. I use a full taylor test kit.

We only run the bubblers when needed to reduce aeration.
We only run the infinity edge enough to keep the chemistry up with the pool AND when swimmers are present to keep from overflowing.

Here are the things I am curious about and am wondering what others are seeing:
1. I was told I would be putting acid in the pool forever. So far that seems to be the case. (~10 oz every other day in the summer) I have given up on achieving 7.5 and look more at 7.7 as a sustainable target. This could play into #3 below.
2. I seem to need to regularly add calcium to keep that up (~4x per year). I adjusted it to 250 about 60 days ago and now it is at 200.
3. I seem to have to add baking soda regularly to keep the alkalinity up. I adjusted it to 100 sixty days ago and now it is below 50.

We have had about 9" of rain in the last two months.

I have not added a lot of other details here that may be necessary in order to keep this post short.

Do others with a similar pool set up see similar things? IF so what are your solutions? It may be that I just have to test often and make adjustments more often. I generally test pH and Cl every other day or so. But sometimes I just pour a bit of acid in the pool and call it good.

The alkalinity is better to stay down near 60 which will keep your pH from rising so fast. That may be your issue. Take a look at the TFP “recommended levels” for more details on why. Your pH will also rise slower if you let it stay around 7.8. No need to keep the pH at 7.5.

 

[SoDel]

For #3, the acid you’re adding will tend to keep TA falling. Just the nature of the beast. Allow for reduced TA target and recommended levels as said by @Bperry .

For #2, the only drop in CH I’ve seen is from losing water one way or another (and low CH fill water). You mentioned 9” of rain — did you need to drain off excess water? If so, that may be where the CH went.

 

[Flavius]

Thanks all.

For #2, the only drop in CH I’ve seen is from losing water one way or another (and low CH fill water). You mentioned 9” of rain — did you need to drain off excess water? If so, that may be where the CH went.

SoDel, due to the infinity edge it takes a small amount of rain for the pool to overflow. THe main pool is always full to the infinity edge level and so 1" of rain makes like 10+ inches of rain in the much smaller infinity edge basin. So it overflows. IT almost feels like most of the chemicals hang out on the surface and overflow with the rain...

As for acid it will pretty quickly goes to 8.0+ in 4-5 days if I do nothing. So I guess I just have to keep dribbling in the acid and keep up with TA without getting carried away.

CH has to be a rain issue and makeup water issue then. It just seems like the rain has a bigger effect than it should. BUt as I said above it doesn't take much rain to overflow the pool. Nature of the beast. With no rain you also have to manage the overflow basin level. Which means adding water. The main pool is ALWAYS full and it comes out of the smaller basin to keep it that way. So I guess an infinity edge is just going to be more of a challenge on level and chemicals. It's not a huge deal. It's just a good bit different than I was used to.

 

[pjt]

I seem to have to add baking soda regularly to keep the alkalinity up. I adjusted it to 100 sixty days ago

Stop adding baking soda. This is the primary source of your pH rise. TA down to 50 is perfectly fine.

I was told I would be putting acid in the pool forever. So far that seems to be the case.

If you stop adding baking soda, your pH will likely stabilize in the high 7s, which is great. Your acid demand will fall dramatically.

Key point: Stop adding baking soda.

What's the TA and CH of your fill water? How much fill water do you use?

 

[Flavius]

What's the TA and CH of your fill water? How much fill water do you use?

The fill water needs to be used pretty much every other day to put ~4" of water in the infinity basin to cover for evaporation unless we get rain. Not to be a broken record but the infinity basin shows all level effects due to rain OR evaporation.

I have not checked the fill water chems other than pH. Which read low. We have well water and a carbon filter system. Ill check the fill water chems today and stop adding baking soda if I have a 50.

 

[Flavius]

On my make-up water from the house:
pH reads below scale. I'm gonna guess a 6.0
CH reads 60
TA is reading at 50

Based on suggestions here I'm adjusting my chem targets to:
TA target at 50-60. I'll take action to raise it at 40 or below to get 50-60
pH target at 7.7 - 7.8 range. I'll take action at 7.9 or 8.0 to lower it closer to 7.7
Unless anyone else has better suggestions.

As for CH I feel like I really need to be 250+ Any suggestions for a hard target? This seems like a critical number for long term integrity of the gunite / pebble coat. The test kit chart gives a range of 200-400 which is pretty wide.

Salt, CL and CYA are all manageable and seam reasonable.

 

[SoDel]

On my make-up water from the house:
pH reads below scale. I'm gonna guess a 6.0
CH reads 60
TA is reading at 50

Based on suggestions here I'm adjusting my chem targets to:
TA target at 50-60. I'll take action to raise it at 40 or below to get 50-60
pH target at 7.7 - 7.8 range. I'll take action at 7.9 or 8.0 to lower it closer to 7.7
Unless anyone else has better suggestions.

As for CH I feel like I really need to be 250+ Any suggestions for a hard target? This seems like a critical number for long term integrity of the gunite / pebble coat. The test kit chart gives a range of 200-400 which is pretty wide.

Salt, CL and CYA are all manageable and seam reasonable.

A suggestion — use the PoolMath app, the subscription version is very inexpensive, and get familiar with how the variables affect your CSI. You can set up more than one pool so name one “test” and you can enter hypothetical test values and see how things interact. Range chemistry is buggywhips at this point lol. Yes, lower TA slows pH rise, but also requires the other variables remain balanced, with pH having the greatest effect. CH at 250 is fine but there's not really any hard target — it’s one of the variables that is usually conveniently stable, at least more stable than the others, fill water use aside, and can be used to balance in harmony with the others. As the seasons change and water temp changes, that might require, for example, bumping TA a bit and letting pH float higher as it gets colder, or bumping CH. Either will work so there’s a bit of do what makes sense based on anticipated temps as well as looking ahead to next season (it’s a lot easier to lower TA than CH after opening, but if your location is like mine, there’s enough new low CH water going in the pool at opening that raising CH before winter isn’t an issue).

If you do stay within the recommended ranges, I think it’s hard to do much harm to the pool, but it’s definitely better to rummage around in PoolMath‘s CSI and get familiar enough with how it all “works” so you can make sure you’re not skirting outside the boundaries of what was anticipated when the recommendations were developed.

 

[pjt]

CH reads 60
TA is reading at 50

I'm jealous of those numbers.

CH and TA rise due to fill water depends on your rainfall, fill water usage, splashout, overflow, etc.. If your CH has been going down over time, I'm guessing your fill water usage is minimal.

I'll take action

Try doing nothing and see where your TA and pH stabilize. You're very close to TA/pH equilibrium, and adding baking soda or MA disturbs that. A TA of 50 is perfectly fine. pH in the high 7s (even 8.0) is also perfectly fine. Add enough calcium to get a CH of 250. Manage your CSI.

 

[Flavius]

Thanks all. Very helpful.