Pool Vac picking up sand/plaster?

[JGrana01]

For the past month or so, my Dolphin robot vac has been picking up some sand/plaster in the bottom if it’s basket. Quite a bit actually.
16K gallon plaster pool, Pentair VSF pump, Pentair SWG. Chemicals are good:
FC. 4.5ppm
pH - 7.6-7.9
TA - ~80ppm
CYA - around 60
Calcium - 300ppm
Salt - I try to keep it no less than 3100ppm

Water temp has been pretty high this past month. Live in Redding CA - July was a baking heatwave - typically 100+ every day, all sun. Pool has been 86F-92F most of the month. I run the Dolphin once a week.

My 3 and 6 year old grandkids have been in the pool more as well this past month.

Is my calcium too low? pH on the high side. Is the pool dissolving?

 

[ajw22]

Pour some acid on a pile of the dirt from the cleaner.

If it bubbles then it has calcium and maybe from your plaster.

If not it is sand and dirt.

 

[JGrana01]

The pool is about 20 years old. In good shape. I purchased the house/pool 2 years ago.
The calcium was pretty low when I started using the TF-Pro test kit.

If it does bubble, and I continue to get this dirt into the fall/winter - anything I can do to slow it down?

 

[ajw22]

You using PoolMath?

Turn on CSI tracking.

Keep your CSI around 0.

 

[Gary Davis]

Keep your CSI around 0.

I have to agree that the saturation being +/- about 0.33 from the zero-crossing point is what you need to keep.
Bear in mind six things affect that saturation index, most of which you can't control all that much.
Mainly you can control the calcium to alkalinity numbers & their respective ratio (usually keeping it around 4:1 at around 400ppm:100ppm).

 

[JGrana01]

Thanks folks. I did a full TF-100 test yesterday.
FC 3.8
CC 0
pH 7.9
Alkalinity 80
CYA 55
Ch 300
Salt 3000
No iron, Cu or Fe

CSI came out at 0.03

I will be putting in the pool vac today. If there is still this stuff on the bottom, I’ll try the acid test and let you know.

 

[ajw22]

Your CYA is 60, we always round up.

Use a 10 ml sample for FC and 0.5ppm per drop. It saves lots of reagent.

 

[JGrana01]

Ok, I ran the Dolphin this afternoon. There again was the white plaster/sand - not as much as the photo I posted.
I poured some Muriatic Acid on the pile - lots of foam :-(

When I purchased the house 2 years ago, I started using the TF-Pro kit. The original owner was not too pool savvy. He told me he just worried about pH and used pucks/liquid chlorine.

When I started testing, FC was ok, pH not bad - but very low CYA and Ch. Over the next 6 months I worked the CYA and Ch up - and upgraded the pump/controller (Pentair Intellicenter and VSF pump). I also installed a SWG and Pentair Heater (heat pump).

I have been keeping the Ch in the upper 200’s now around 310.

My CSI value (according to Pool Math - great app!!!) is typically .01 - .06

Not sure what else I can do.

Is it re-plaster time?

 

[reggiehammond]

I have to agree that the saturation being +/- about 0.33 from the zero-crossing point is what you need to keep.
Bear in mind six things affect that saturation index, most of which you can't control all that much.
Mainly you can control the calcium to alkalinity numbers & their respective ratio (usually keeping it around 4:1 at around 400ppm:100ppm).

Positive CSI for a SWCG is the kiss of death. OP needs to keep CSI at 0 to -.6 to avoid scale in the SWCG and reduced cell life.

@JGrana01 - have you looked at the plates in the SWCG?

 

[JoyfulNoise]

What kind of filter does your pool have?

 

[Gary Davis]

Positive CSI for a SWCG is the kiss of death. OP needs to keep CSI at 0 to -.6 to avoid scale in the SWCG and reduced cell life.

Oh. I see. I missed that it was a SWCG pool but looking back, I see that in the original post. My bad. Thanks for clarifying that mistake so that the OP knows what to do.

When I started testing, FC was ok, pH not bad - but very low CYA and Ch. Over the next 6 months I worked the CYA and Ch up

Just curious, while free chlorine changes daily and pH can change weekly, why would it take half a year to raise cyanuric acid and calcium hardness?
While it seems like it takes forever for the cyanuric acid granules to dissolve, they don't take that long.
And calcium pellets, while they heat up the five gallon bucket when dissolving in water, only take a few minutes to dissolve.

What often can take a while is LOWERING CYA, CH and/or TA.

 

[JGrana01]

Positive CSI for a SWCG is the kiss of death. OP needs to keep CSI at 0 to -.6 to avoid scale in the SWCG and reduced cell life.

@JGrana01 - have you looked at the plates in the SWCG?

Yes, in fact just this past weekend. I did see some scale - not terrible but definitely there. I did an acid wash - plates are nice and clear now. Also, Salt level reading seems to be improved.

I had never heard about CSI being negative. Last I checked, CSI was + 0.15.

In using the calculator in Pool Math, I see if I can get my pH down to around 7.6, it drops my CSI to -0.10.
I also see the temperature as an effect.

Is managing the pH the way to go?

 

[JGrana01]

What kind of filter does your pool have?

Jandy cartridge - CLV-460. I had replaced the cartridges this past May.

 

[JGrana01]

Oh. I see. I missed that it was a SWCG pool but looking back, I see that in the original post. My bad. Thanks for clarifying that mistake so that the OP knows what to do.

Just curious, while free chlorine changes daily and pH can change weekly, why would it take half a year to raise cyanuric acid and calcium hardness?
While it seems like it takes forever for the cyanuric acid granules to dissolve, they don't take that long.
And calcium pellets, while they heat up the five gallon bucket when dissolving in water, only take a few minutes to dissolve.

What often can take a while is LOWERING CYA, CH and/or TA.

Sorry for the confusion. I should have said, “I have been raising the CYA very slowly - after reading all the threads and information on TFP, the last thing I wanted was to overshoot.
So, I was only adding a few pounds over a few months.
As far as Calcium - I did initially put in a large amount over a year ago. After this past winters rains, I saw the Ch drop - so again I have added 4 lbs at a time over the past month.

Thanks!

 

[reggiehammond]

Yes, in fact just this past weekend. I did see some scale - not terrible but definitely there. I did an acid wash - plates are nice and clear now. Also, Salt level reading seems to be improved.

I had never heard about CSI being negative. Last I checked, CSI was + 0.15.

In using the calculator in Pool Math, I see if I can get my pH down to around 7.6, it drops my CSI to -0.10.
I also see the temperature as an effect.

Is managing the pH the way to go?

Yes, pH is a big driver, but actually managing TA is the way to gain hold of your CSI. Once TA is lowered to 50-60, you'll see that the pH becomes very stable and the CSI is in a great place.