New Pool Construction - Rising CH & pH

[ncbart]

New pool owner here, and as title suggests, I'm battling a constant pH and CH rising. Minipebble plaster went in June 22, and was filled immediately after. Calcium hardness is already up to 600ppm and pH is constantly rising, and reached 8.0 within 2 or 3 days of not paying attention last week. I added enough acid to bring it back down to 7.4, but it shoots back up to 7.6 within 24 hours. I've been going through this cycle for the past week or so. Unfortunately, I only recently bought a Taylor K-2006 kit last week and recording measurements, so the only previous measurement I have is at Leslie's. I know pool stores are notorious for giving inaccurate values, but this is the only comparison I have.

Is it normal to go through this pH and CH rising so quickly in the first month? I'm aware the water chemistry can be unstable as the plaster cures, especially the first month. I did use 2 lbs of Cal-Hypo shock a week ago, but didn't think 2 lbs is enough to bump up CH to 600 ppm in a 20k gallon pool? Also, in terms of aeration, we do have a 4 sheer descent waterfalls and a standard spa spillway, but the sheer descents are rarely turned on.

Other than the rising pH and CH, pool water looks great and is crystal clear.

Any suggestions going forward? Thanks!

From Leslie's on 7/13:
FC - 5ppm
CC - 0.2
pH - 7.4
TA - 90
CH - 260
CYA - 60

Here's my values from today:
FC - 9ppm (I know this is high, trying to get my in-line feeder dialed in)
CC - 0.5 (possibly lower, used .5ppm increments)
pH - 7.6
TA - 120
CH - 600
CYA - 60

 

[Divin Dave]

Hi and welcome to TFP.

New pools pH does rise very quickly during the curing process which can last for several months, so that doesn't surprise me at all.

the CH on the other hand shouldnt be rising unless the water you use to replenish that which has evaporated, is very high in CH. I suggest you check your tap water to see if thats the source of the calcium rise. But to be honest, rising from 260 to 600 in less than a month seems somewhat incredible. I suspect a testing error might have some influence on it

 

[ajw22]

Welcome to TFP.

New Plaster + spa spillover always running (?) + TA OF 120 = rapidly rising pH.

Lower your TA to 60. What is the TA of your fill water? You have an autofill?

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

Do you have automation to control when your spillover runs?

CYA 60 is high for a tablet chlorinated pool. What do you have in your inline chlorinator? Trichlor tablets are going to keep adding to your CYA. Read ...

How to Chlorinate Your Pool

Before chlorinating your pool, you should know these simple tips. Learn the best way to add chlorine to your pool.

www.troublefreepool.com

 

[Tena]

I also have a fairly new pool. Cal-hypo does raise CH.
But, that's a big jump.

Alkalinity high and aeration both raise ph, as well as new plaster. So that will be an ongoing battle. I have only people aeration and my ph is still on the rise.

I was using liquid chlorine and muriatic acid regularly. We converted to salt after 30 days so now I'm just adding acid.

 

[ncbart]

Thanks all for your comments. I'll try lowering the TA as you suggested. I don't mind regularly adding acid, but having to put it in everyday is a bit much. As for the high CH, I also thought that Leslie's might have messed up the measurement. I've done the measurement myself several times over several days, and get a consistent 600ppm.

Yes, we have an autofill, and I can turn off spa circulation via a valve. It's a good idea to try testing the fill water to at least eliminate it from the possibility. We have city water here, so I don't expect very high levels of CH or TA, but I might be in for a suprise.

Also, regarding the chlorine, I use Triclor with an inline feeder. I'm a bit puzzled why my CYA levels are already so high with a month-old pool. The only thing I think of is I had the dial pretty high for a while. The previous test kit wasn't a titration kit like I have now, so I'm guessing I had way more chlorine than I previously measured and could explain why CYA is so high.

Knowing that the only true way to reduce CH and CYA is by dilution, do you think it would be worthwhile to do a partial drain and refill soon (assuming hard city water isn't the issue)? I was thinking of doing it once summer ends and it cools down. Will there be any issues doing this with new plaster?

 

[ajw22]

@mknauss can provide a water exchange method.

 

[mknauss]

You can exchange some water without draining.

If you place a low volume sub pump in the deep end and pull water from there while adding water in the shallow end (through a skimmer or into a bucket on a step so you lessen the water disturbance) you can do a fairly efficient exchange. That is assuming the water you are filling with is the same temperature or warmer than your pool water. If your fill water is much cooler than your pool water, then switch it. Add the water to the deep end (hose on bottom) and pull water from the top step.

The location of the pump and fill hose may change if you have salt water, high calcium, etc.
In my pool, with saltwater and high calcium when I drain, I put the pump in the deep end and hose in shallow end. The water in the pool weighs more per unit volume than the fill water from the hose.

Be sure to balance the water out and water in so the pool level stays the same. Also be sure your pool pump is disabled during this process. Once started do not stop until you have exchanged the amount of water you wish.

 

[ncbart]

Evening folks,

Just as an update to what we discussed, the fill water has a CH of 200ppm and TA of 150ppm, so the high CH I'm experiencing doesn't seem to be coming from the fill water. Now that I think of it, I recall seeing a bag of calcium chloride when the pool builder was doing the first water balance after the initial fill. Perhaps they put too much calcium chloride initially, which added additional calcium on top of the 200ppm coming from the fill water. I just lowered the pH to 7.2 and will let the pool aerate and repeat until I get my TA to a lower range, so thanks for that suggestion.

Regardless, I think given the high CH and CYA, I'll do some type of water exchange or dilution. Thanks for the instructions for the water exchange, it looks relatively straight forward. Just curious, would it not be the same to isolate the main drain valves and dump water using the pump while filling up with a hose in the shallow end? If I had to guess, the biggest issue might be that you dump water faster using the pump than you can fill up with a hose?

 

[mknauss]

I do not like to use a $1000 pump for a job a $100 pump can do. Up to you.

 

[ncbart]

After about 2 weeks, I've been able to lower the TA to 80 using the recommended aeration, on my way to the goal of 60 as suggested. I still find the pH creeping up about +0.2 each day, so I'm having to add approx. 30oz of muriatic acid every other day to bring it back down to 7.2 to restart the aeration process. Does anyone know if there's any adverse effects of adding this much acid almost daily? I've been adding it slowly in front of a return jet in the deep end above the main drains (deep end depth is 6.5 ft), so I think it's diluted enough not cause any issues. I just worried in the long term, I'm slowly etching my plaster by adding this much acid.

On a positive note, I did find the CH decreased to 525. I'm not sure how considering I never did a water exchange, but 2 separate tests confirm it's slightly lower. It's been very hot and dry here lately with the pool temp around 91 °F during the day.

 

[mknauss]

No issue in adding the acid as long as it is well mixed. Your TA is dropping so the acid is consuming it.

Your CH could not have decreased. Just testing error. But not an issue.