Keep having to acid wash my pool, HELP! Calcium hardess just keeps rising

[Neoex]

My pool is approx 18 months old and I am about to have it acid washed for the 3rd time. The finish is pebbletec pebble fina.

Long story short the calcium hardness steadily rises until I get calcium buildup that looks like white scale marbling all over my pool.


The tap water in my city is 200 out of the faucet but it keeps rising 15-20pts per week without fail.

I keep my PH at 7.5-7.7 (sure it has been at 8.0 for a few days, im not perfect, but i balance my pool 2x a week)
ALK runs approx 80-90
Calc harness 300-550 (once i got to 450 i drained it 30% and filled it back up and it went down to 300 then slowly rises again).
CYA 45
Chlorine 2-4


I do not shock the pool I just let the SWG control the chlorine via the iChlor. I occasionally add a small amount of Alkalinity up and Scale-Tec.

my PB is totally stumped but he thinks the applicator of the PebbleTec maybe responsible. He said based on the temperature outside at the time of application they add a certain amount of calcium to get the product to a proper viscosity to apply it. He thinks they maybe "over did it" on the calcium and now its just slowly over time leeching out through the plaster. I really have no other feasible ideas, nor does my local pool store or the company that balances my pool.


Anyone have any ideas?

 

[Texas Splash]

After 18 months the pebble should be fully cured and not an issue. As long as you aren't adding any cal-hypo on occasion, I suspect your biggest enemy is wind and evaporation resulting in top-offs. I certainly loose a good amount of water to wind and evaporation. I will add that you don't need to use Alk Up, and actually should try lowering the TA just a bit more - say about 60. That should help keep the pH steady and not rise quite as fast. Those actions might help keep your CSI more to the neutral or slightly negative to prevent additional scale build up.

 

[Neoex]

well my pool has a small leak which is actually working in my favor because its adding in auto-filler water (200 hardness) and helping mitigate the scenario but as this leak gets fixed its just going to exacerbate the hardness rising. I am not putting cal-hypo in the pool

 

[Sunnydaze]

well my pool has a small leak which is actually working in my favor because its adding in auto-filler water (200 hardness) and helping mitigate the scenario but as this leak gets fixed its just going to exacerbate the hardness rising. I am not putting cal-hypo in the pool

Adding fill water is what continues adding calcium to your pool. You're likely adding more water than you're losing from the leak because you're also losing water via evaporation.

Are you sure it's rising 20ppm each week? How are you testing?

 

[Neoex]

no sorry maybe my message wasnt clear. my fill water from my tap is 200PPM, so its actually lowering it, my pool is currently around 515 and raises 15-20PPM. I am taking water samples to the pool store and they are testing the water.

Please lets not turn this into a water test kit thread. The PPM is steadily rising on every test including one that my PB has run himself

 

[aussieta]

i think you may have more evaporation than you are calculating for
but as they say GIGO garbage in garbage out
you may spend more time and money to find it is test errors

 

[Texas Splash]

my fill water from my tap is 200PPM, so its actually lowering it, my pool is currently around 515 and raises 15-20PPM.

Perhaps there's a misunderstanding. Let's assume your CH is actually 500 right now and your autofill adds 100-200 gallons of water this week. Just because the fill water is 200 doesn't mean your CH will go down, at least not if the water loss is primarily from evaporation. The CH of 500 is still in the pool, and you're adding to it. The only way the CH might go down is if your water loss is due to a verified pool leak, but then you would also see a loss in CYA and salt as well. A fill water of 200 is high enough to warrant careful management over the season.

That brings us to your next note ...

Please lets not turn this into a water test kit thread.

We certainly can't force any pool owner to get a particular test kit, or use a certain sanitizer. All we can do is advise. In our experience a thousand times over, no one will provide you with consistent, accurate testing more than yourself with a proper test kit. While the store and builder might be in agreement your CH is slowly rising, their actual test level(s) may be inaccurate or inconsistent which will directly impact what pH and TA you should be maintaining. In the end, it's 100% your call. I suspect your fill water is continuously adding to an already slightly elevated CH level of ~ 500, and this can easily be managed (to prevent scale) by managing the pH and TA to keep the CSI slightly negative on the PoolMath APP.

 

[YippeeSkippy]

Many people out west who *suffer* with high calcium levels learn that keeping their pH on the low side (7.2) helps balance their CSI, which helps things.

Have you considered monitoring your CSI with PoolMath?

Maddie

 

[BenB]

my fill water from my tap is 200PPM, so its actually lowering it

Texas Splash said the same above, but wanted to agree with him that you've misunderstood how this works, and it's not immediately intuitive as it's different for different properties of water.

Some properties, like pH, work the way you are thinking - that mixing new and old water will result in an average of the two coming out.

Most, however, that involve "stuff dissolved in water" do not work this way but instead are additive. Think of it this way - when you add 1 gallon of water, think of it as the plain water, but also a cup of calcium powder. Now that calcium powder is in your pool. Adding more water won't reduce the calcium that's now in there - rather you're adding yet another cup with each new gallon.

Evaporation in a pool works like it does on your stove or kettle - the pure water boils off but leaves of all the dissolved solids behind (for pools, most relevant are calcium, salt and CYA). But now you have to top off the water, which will add another 'cup' of calcium since you have it in your fill water.

Over time therefore the calcium level will always go up - even if your fill water has less CH than your current pool level. In fact unless your fill water CH is literally zero, it will accumulate over time.

The only meaningful way to actually remove calcium is to pump it out, and then replace with fresh. That process will behave in the way you expect, since you are mixing new and old water to bring it back up to the previous volume.

 

[mgtfp]

Not much to be added to the above. Looks like you will have to find strategies to cope with CH creeping up to minimise the times you have to drain and refill.

In the end, it's about CSI management by controlling TA and pH as already discussed. To support that, I'd recommend to increase your CYA level to the SWG recommended levels of up to 80ppm.

There is a nice side effect of the increased CYA-level (apart from having better protection of your chlorine from UV): You are replacing Carbonate Alkalinity with CYA-Alkalinity (keeping Total Alkalinity constant). It is Carbonate Alkalinity that contributes to the CSI (PoolMath internally uses TA and CYA to calculate Carbonate Alkalinity).

That will help to reduce CSI.

And the better UV protection will enable you to run your SWG less, which will reduce scaling on the SWG plates.