Lowering TA, how long to aerate?

[FastCougar]

So, I just opened my pool on July 6th and my TA was measuring 250. After lowering the ph from mid/high 7's (7.6-7.9) to 7.0 and aerating twice (once with pool full of splashing kids after running a home-made aerator for a hour and again with topping off the pool with the water hose on "jet"), I'm down to 170. I want to get down to 80 or 90 before adding Borates, so I just dropped the PH from 7.8 to 7.0 (or slightly lower) and I'm currently aerating. I'm pointing the return jet upwards and it's aerating quite well, but it's also midnight and has been aerating for about 2 hours now ... should I continue this through the night or shut down and test in the morning and continue if needed?

 

[chem geek]

You can keep aerating through the night if you want. The pH will slow down in its rise so you probably won't get too much above 7.8. The most efficient approach is to keep adding acid to keep the pH low near 7.0 since the aeration will drive off more carbon dioxide faster at lower pH (see this chart to see how over-carbonated the water is at various pH and TA levels).

 

[FastCougar]

well, I didn't want it to run all night because the water level has been on a slight decline as of late due to full sun conditions and my reluctance to install the solar blanket until I come up with a solution to getting it out of the pool and hung up so it doesn't sit in the grass. I was afraid that the pump would start pulling in air, so I shut it down around 1AM ... tested the water this morning around 10:30AM and the TA had dropped from 170 to 120 and my PH was around 7.2. I dropped a hose in, added about 1" of water while also adding in 32oz of MA and continued aerating. I figure between the water addition and the calcs based on more water than I had, the PH would be brought from 7.2 to around 7.0-7.1. It's been aerating about 3 hours now ... at the 5 hour mark I plan to retest TA, PH & FC/CC ... I'm prepping for Borate addition and need to bring my TA down from initial fill and chemistry when it was sky high at 250-260 range. I'm shooting for 80-90.

 

[anonapersona]

You might want to test the TA of your fill water.

 

[FastCougar]

very good point, I took your advice and tested ... I'm going to have an uphill battle on my hands here ... the fill water (tap from city water source in Martinsburg, WV) has PH of 7.0 and a TA of 250-260

So, what are my options other than using a solar blanket regularly to avoid evap to minimize refilling? Does this mean I will have to keep a steady supply of MA on hand and aerate immediately after refill? Or can I forgo the TA monitoring and simply add the Borates with the high TA?

 

[anonapersona]

No borates right now I think, but that's not something I know much about.

But, high TA I am familiar with, my tap TA is 340. Yes, you can expect to add acid every other day our so when you are using tap water to refill the pool, and even if you are not, until TA goes down some.

Of course, rain water will have no TA, so you will just have to pay attention. Don't, for example, refill the pool if there is a good chance it will rain.

My pool has enough built-in aeration that I no longer "work" on lowering TA, I just adjust to 7.2 and let it go up on it's own. Once in awhile I get peeved and push it to 6.8 but I do worry about the waterfall rocks then, they are decaying a bit and I don't need to aggravate that.

I had lowered the pool to a reasonable level, then had 3 weeks of using trichlor tablets and now at TA 70, pH is weirdly stable. I'm not used to this, very strange.