trouble keeping PH in range

[CARSON]

Hello everyone! I have a new gunite pool (finished in October 2011) and am having trouble keeping the PH in the desired range, it keeps rising.

I am using a SWG for chlorination, my pool is 14,000 gallons and I am using one gallon of muratic acid every two days on average. I use the TF-100 test kit and got readings this evening about 6:30 pm. I live in the Houston area, the pool is in full sun all day. I run my pump from 7:30 am to 6:00 pm. Pentair Intelliflow pump at 1700 rpm with a 60 sq ft DE filter, I am able to turn the pool over twice daily at the current pump time. The SWG is at 80% and the water is crystal clear!

The readings iI got are;
FC 4
CC 1.5
TC 5.5
PH 7.8 (added acid yesterday)
TA 40
CH 820
CYA 70
Salt ranges from 3,600 - 5,000 (according to my circupool SWG )

I am not sure if the CH test is accurate, I tested a friends CH for him and got over 500 then he got a reading from the pool store and they got 300. I feel confident in my other tests.

I appreciate any suggestions, acid is $6 a gallon and is the most expensive maintenance cost for me by far.

I have added baking soda several times according to the pool calculator without much success in getting the TA up to the desired rang for a salt pool.

 

[BoDarville]

Hi CARSON:

What is your pool's surface (the part that comes in contact with the water) - Plaster, Vinyl, Fiberglass, other? Recommend adding that to your signature as that surface is more relevant for certain tests, namely CH. Gunnite is the outer shell; the actual surface is applied on top of that before filling with water.

If the surface is plaster, it is not unusual for the pH to drift up, especially in the first year. Here is an article on starting up new plaster: http://www.troublefreepool.com/pool-school/pool_plaster_start-up

The CH reading of 820 is high - shouldn't be over 400 regardless of surface. BTW, I would trust your test results over the pool store's. I would retest it again to confirm, though. A high CH along with stubbornly high pH could lead to calcium scaling. Therefore if you confirm a CH of over 400, I would take steps to lower it. The only 2 methods to lower CH are:

• 1. Replace water with a lower CH water source (tap or rain water)

• 2. Hire someone to do a Reverse Osmosis treatment on your pool water ... which actually also requires some water replacement.

Finally, your CC of 1.5 indicates a need to shock. Here is the process: http://www.troublefreepool.com/pool-school/shocking_your_pool

 

[JasonLion]

The PH, TA, and CH will all rise very rapidly for the first 30 days, and more slowly for up to a year after fresh plaster is applied. Adding acid daily during the first month is very common.

The constant acid additions will tend to also lower the TA. Try to keep TA up at 50 at the very least.

When doing the CH test, did the sample ever turn purple. Turning purple is called a floating end point and tends to result in higher than actual test results.

 

[CARSON]

Thanks for your posts!
BoDarville, the surface of the pool is quartzscape plaster. I also forgot to mention that my spa overflows into the pool, I have learned that this will cause PH to drift up also. I do keep the amount of water that overflows to the pool to a minimum.

I will recheck the CH reading, I use tap water to fill the pool, took advice from this site and checked my tap water before filling. I got a realitivly high (for tap water) reading there too, I think it was about 280 but will recheck it. If that was a good reading then it seems like replacing with this tap water to lower CH would be a full drain and refill as opposed to replacing with water that has closer to 0 CH. I hope I don't have to do that, seems like a waste of good water. I hate wasting water.

I will also shock the pool, I have not shocked it yet and will use the link you provided.

Jason, now that you mention it I seem to remember that the water turns purple everytime I perform the CH test. I was looking for blue like the test kit says but figured the purple color was close enough. Any suggestions on what I can do to get a more accurate result? I was thinking about taking a sample to the pool store but BoDarville is not the first person to suggest that a result from the TF-100 kit is more dependable than the pool store.

I will add baking soda again in attempt to raise the TA to the desired range.

Thanks again for your time and suggestiong.

 

[BoDarville]

CARSON:

If the CH of your fill water turns out to be around 280, it may be tough to maintain a CH of less than 400 in the pool. If that's the case, a complete or partial drain & refill may not be the best option in this situation. Aside from the cost-benefit being questionable in that case, I too hate wasting water and we don't have water to waste in Texas. On the other hand, if the CH of your fill water is closer to 0, then a partial drain & refill becomes a more attractive option.

Although the ideal CH for plaster is between 250 - 350 ppm, higher levels can be managed by keeping pH and TA on the low side to reduce the risk of calcium scaling. I would take steps to lower your pH from the current 7.8 to around 7.5. I use MA, but you can also use dry acid. The addition of acid will also tend to lower your TA. Since that is already a bit low, so you will need to add some Baking Soda to increase that to at least 50 as Jason suggested. Fortunately Baking Soda has virtually no impact on pH. Nevertheless, you may have to do some fine-tuning between acid additions to lower pH (especially with your waterfall) with simultaneous Baking Soda additions to keep TA in check.

 

[HouTex]

Thanks for your posts!
BoDarville, the surface of the pool is quartzscape plaster. I also forgot to mention that my spa overflows into the pool, I have learned that this will cause PH to drift up also. I do keep the amount of water that overflows to the pool to a minimum.

I will recheck the CH reading, I use tap water to fill the pool, took advice from this site and checked my tap water before filling. I got a realitivly high (for tap water) reading there too, I think it was about 280 but will recheck it. If that was a good reading then it seems like replacing with this tap water to lower CH would be a full drain and refill as opposed to replacing with water that has closer to 0 CH. I hope I don't have to do that, seems like a waste of good water. I hate wasting water.

I will also shock the pool, I have not shocked it yet and will use the link you provided.

Jason, now that you mention it I seem to remember that the water turns purple everytime I perform the CH test. I was looking for blue like the test kit says but figured the purple color was close enough. Any suggestions on what I can do to get a more accurate result? I was thinking about taking a sample to the pool store but BoDarville is not the first person to suggest that a result from the TF-100 kit is more dependable than the pool store.

I will add baking soda again in attempt to raise the TA to the desired range.

Thanks again for your time and suggestiong.

Carson, I'm in Houston and I also have a quartz pool with a spill over spa and a SWG. While my pump is larger, which probably accounts for more pH rise, my pH is still rising and my pool was finished in December 2010. I'm also fighting high CH--my fill water is CH 150, and constitently rising TA--fill water TA 220. I'm trying to keep my TA around 50-60, but it's hard unless we get a lot of rain. But it's better than the first 4-6 months. I'm probably adding about 1.5 gallons of MA each month to keep pH around 7.6 or so. When I'm trying to lower TA I'll go through a gallon in about 10 days or so. Other than the inconvenience of adding MA and except for the occasional topping up of CYA and Borates, my pool pretty much takes care of itself.

 

[XsAllOverIt]

I've got a 22000 gallon pool that's close to 2 years old. I add probably a gallon every 9 days to my pool to keep the pH in check. I too have an SWG and a waterfall from the hot tub to the pool. I have elected not to add Borax to my pool due to dogs.