pH rising out of control

[zgjs02]

My pool is 3 years old and pH has never really been stable, even though I've added borates to the water and reduced flow over the waterfall. I started noticing black gravel-like stuff in the bottom of the pool last year but this year it's everywhere every time I brush. Over the last month or so, my pH rises from 7.5 to 8.0 in 2 days. My latest chemistry is CL 4.0, Alk 90, borates 70, CA 270, CYA 100. How can I stop this rapid pH rise and is this gravel-like stuff pebbles? Thanks!

 

[Newdude]

Hey Z and belated Welcome !!!

Alk 90

Has it always been 90 ? It should fall pretty quick if you're dosing Muriatic acid frequently to lower the Ph, then once it's 60 it'll help the Ph be more stable.

my pH rises from 7.5 to 8.0

Have you confirmed you hit the target, or just dose and assume ?

reduced flow over the waterfall

To 15 mins just to cycle it, or 12 hours from 18 ?

 

[zgjs02]

No, I usually try to keep Alk at 60-70 but we've had a lot of rain recently and the Alk fell to 50, which I assumed was too low, so I treated a bit agressive to get it back up. I am using a Sutro pool monitor and confirm readings when I suspect them with a Taylor test kit with your reagents. Sutro has been pretty accurate. According to the pool builder, I should run my variable speed pump at 2850 rpm for 1 hour for every 10 degrees of air temp. So right now I'm running it on high for 9 hours a day and at 1740 rpm for 15 hours. This keeps the spa filled and barely overflowing, on high I've reduced the flow into the spa to where the overflow is 30-40% of what it would be if the valve was fully open.

 

[sande005]

I know nothing about plaster pools - so can't help to tell you if the pebbles are from that, although I assume unlikely. I'd start by close looking at the surrounding conditions. Might it be from degrading mortar eroding out from tile/stone joints? How do things look on the underside of the coping around the pool? Ditto for any areas surrounding jets/skimmers/etc., etc. What kind of roofing is near by - is it carried by run off from that (may be accumulation also in gutters, if you have them).

As noted, with the high TA, your pH will rise pretty fast. Drastacly cutting back the waterfall time will assist. Time to be more aggressive in the acid adds - lower to 7.2, and when it gets to 8, lower again. Test your TA and when it gets near 60, the pH should stabilize pretty well in the high 7's.

Your CYA is really high, as you no doubt realize. Are you using tablets in the Cl feeder? That would be the cause. You need to stop using those now, and start adding liquid Cl daily to keep it at a level of 11-13. Plan for a replacement of much of the water to get the CYA down.

 

[setsailsoon]

Zg,

Welcome to TFP! Sorry to hear you are having pool issues but that's how most of us got here too. This is the best place you can get great advice because we have experts and pool enthusiasts that volunteer to help plus we don't sell anything so you can be sure your getting unbiased advice.

I had similar problem with my previous pool and experts here suggested I lower TA to 50 and run Ph at 7.8 to 8. That helped a lot and adding borates reduced the frequency of acid but didn't reduce total acid. Over time my pool chemistry stabilized a lot so I stopped adding borates. For some reason I just believe my plaster took longer to cure than most. But it did eventually cure.

The gravel/sand you are finding is likely just coming in from outside the pool. Have you had a lot of rain or dry windy weather? This could be the culprit.

I hope this helps.

Chris

 

[zgjs02]

Zg,

Welcome to TFP! Sorry to hear you are having pool issues but that's how most of us got here too. This is the best place you can get great advice because we have experts and pool enthusiasts that volunteer to help plus we don't sell anything so you can be sure your getting unbiased advice.

I had similar problem with my previous pool and experts here suggested I lower TA to 50 and run Ph at 7.8 to 8. That helped a lot and adding borates reduced the frequency of acid but didn't reduce total acid. Over time my pool chemistry stabilized a lot so I stopped adding borates. For some reason I just believe my plaster took longer to cure than most. But it did eventually cure.

The gravel/sand you are finding is likely just coming in from outside the pool. Have you had a lot of rain or dry windy weather? This could be the culprit.

I hope this helps.

Chris

thanks for the input, I have compared the shingle grains to what is in the pool and they are significantly smaller than whats in the pool and the only downspout that is closest to the pool empties directly into the pool overflow drain and deck drains. There is grass and artificial turf around the pool so I just can't imagine where a gravel-like stuff would blow into it? Yes we have had 3-4 " of rain a few weeks ago but nothing significant since.

 

[Newdude]

I am using a Sutro pool monitor and confirm readings when I suspect them with a Taylor test kit with your reagents

Ok GREAT. You're free to use other methods, providing you can easily prove/disprove them if you get a hunch they're off.

According to the pool builder, I should run my variable speed pump at 2850 rpm for 1 hour for every 10 degrees of air temp

They don't even know what they don't even know.

The pool needs 15 mins to mix. Twice a day is even better. The spa may need a little longer to exchange itself.

If crud falls in the pool, it needs to be filtered. You need longer run times in the spring and fall and much less in the mid season. Anyone saying that everyone needs X is full of it. You need what you need, *when* you need it.

You can have trees between you and the neighbor and it all blows your way. You needs tons of filtering, he needs next to none. That's 2 neighbors. Imagine all the pools in the land and the differences they see ?

But if the industry picks high enough #s, they were right that you are filtering 'enough'.

 

[zgjs02]

I know nothing about plaster pools - so can't help to tell you if the pebbles are from that, although I assume unlikely. I'd start by close looking at the surrounding conditions. Might it be from degrading mortar eroding out from tile/stone joints? How do things look on the underside of the coping around the pool? Ditto for any areas surrounding jets/skimmers/etc., etc. What kind of roofing is near by - is it carried by run off from that (may be accumulation also in gutters, if you have them).

As noted, with the high TA, your pH will rise pretty fast. Drastacly cutting back the waterfall time will assist. Time to be more aggressive in the acid adds - lower to 7.2, and when it gets to 8, lower again. Test your TA and when it gets near 60, the pH should stabilize pretty well in the high 7's.

Your CYA is really high, as you no doubt realize. Are you using tablets in the Cl feeder? That would be the cause. You need to stop using those now, and start adding liquid Cl daily to keep it at a level of 11-13. Plan for a replacement of much of the water to get the CYA down.

thanks for the input, yes I'm using a tablet feeder with PoolLife MPT Extra tablets. I just recently started using them and was getting suspicious that they might be the cause of my pH issues. I used to use Leslie's tablets which caused a pH rise but over a week and not 2 days. I was planning a 40% water swap but may have to do it twice. When you say liquid CL to a level of 11-13 ppm? Not sure I understand that.

 

[Newdude]

There is grass and artificial turf around the pool so I just can't imagine where a gravel-like stuff would blow into it?

Got any nearby neighbor kids throwing their gravel to hear the plunks?

 

[zgjs02]

Got any nearby neighbor kids throwing their gravel to hear the plunks?

nope, no gravel anywhere around me.

 

[TinFoilHat]

Do you have a rock waterfall or other rock features around the pool? My waterfall will shed sand into the pool. Could it be the pebble finish degrading? Have you ever acid washed?

 

[mknauss]

What material was used under your artificial turf?

 

[sande005]

thanks for the input, yes I'm using a tablet feeder with PoolLife MPT Extra tablets. I just recently started using them and was getting suspicious that they might be the cause of my pH issues. I used to use Leslie's tablets which caused a pH rise but over a week and not 2 days. I was planning a 40% water swap but may have to do it twice. When you say liquid CL to a level of 11-13 ppm? Not sure I understand that.

Pool School here has a lot more about it, but essentially, the more CYA you have, the higher your FC level must be to remain effective. Since tablets add CYA, it increases over time, and if you up the output of the chlorinator it just adds more, faster. To the point where it is unsustainable.
So at 100 - you need lots of FC in your water.

Below is the chart as to what levels to be at, based on CYA amounts, in ppm terms.

The Minimum is just that, and at that level, you are in danger of dipping too low between tests and allowing algae to grow.
Note that, unfortunately, above levels of 9-10ppm FC, the pH test becomes unreliable. So also a problem measuring that.

The SLAM section is what you have to bring your FC level to, for a sustained period (days, many days) to kill off existing algae.

In simplistic terms, the CYA absorbs a lot of the FC (that still shows up in your tests, but is not active). As you loose FC, some of that absorbed FC is released back and becomes active again. Hence why some CYA is good - it acts as a buffer from going too low. But there are limits as to what it will give back.

Salt water generators are much more consistent in replenishing CL, so one can run at lower levels, with less risk of going too low. But they aren't good at rapidly increasing levels, hence why the recommendation to run with a higher CYA level than a pool without one.

The only way to reduce CYA is to replace the water with fresh.

 

[zgjs02]

Do you have a rock waterfall or other rock features around the pool? My waterfall will shed sand into the pool. Could it be the pebble finish degrading? Have you ever acid washed?

No, the waterfall is just layers of travertine coping stacked. I think the pebble finish is degrading but would water having access to the plaster layer behind the pebble affect the pH? The builder acid washed the plaster when they installed but no I have not.

 

[zgjs02]

Pool School here has a lot more about it, but essentially, the more CYA you have, the higher your FC level must be to remain effective. Since tablets add CYA, it increases over time, and if you up the output of the chlorinator it just adds more, faster. To the point where it is unsustainable.
So at 100 - you need lots of FC in your water.

Below is the chart as to what levels to be at, based on CYA amounts, in ppm terms.

The Minimum is just that, and at that level, you are in danger of dipping too low between tests and allowing algae to grow.
Note that, unfortunately, above levels of 9-10ppm FC, the pH test becomes unreliable. So also a problem measuring that.

The SLAM section is what you have to bring your FC level to, for a sustained period (days, many days) to kill off existing algae.

In simplistic terms, the CYA absorbs a lot of the FC (that still shows up in your tests, but is not active). As you loose FC, some of that absorbed FC is released back and becomes active again. Hence why some CYA is good - it acts as a buffer from going too low. But there are limits as to what it will give back.

Salt water generators are much more consistent in replenishing CL, so one can run at lower levels, with less risk of going too low. But they aren't good at rapidly increasing levels, hence why the recommendation to run with a higher CYA level than a pool without one.

The only way to reduce CYA is to replace the water with fresh.


View attachment 609641

ok thanks for the explanation, I'll read up more in pool school and start the water swap. I don't have any algae as I'm using a tablet that has an algaecide in it, but I did have an algae issue that's why I'm using it... so this makes a lot of sense. thank you again

 

[zgjs02]

What material was used under your artificial turf?

crushed concrete I believe. (white)

 

[Newdude]

90+ CYA is sketchy at best to read and it may be much higher than the 100 you're seeing. Mix up a batch of half pool and half tap. Use that as your sample and proceede with the rest of the test as normal. Double the result to see if it's actually near 100, or more.

The tabs have to go or they will swamp you.

Also, algecide is counterproductive during the season . It fights it out with the chlorine, leaving you with less of each. Ironically, then you need the algecide that you no longer have.