Pool pH keeps rising. Could it be the returns in my spa?

[jmut13]

Hello all,
First post here and first time pool owner. I purchased a home with an existing 24k gallon IG plaster pool in south Texas. This pool is L shaped and has a small spa located on the inside of the L as you can see in this photo. The plumbing is connected for both. My math says the pool and spa make about 24.8k gallons combined.

We emptied the pool completely and gave it an acid bath last week. I've since refilled and slowly getting my numbers right. Here is what I have right now.

FC 8 - Will be keeping around 6.
CC 0
TA 100
CH 150 - Will be receiving 25LB of Calcium Plus from Robelle tomorrow.
pH 8.0
CYA 35 - Still adding dry cya in a sock. Goal is 50-60.

I've noticed my pH continues to rise from 7.5 to 8.0 daily. I bring it back down to 7.5 with 24oz of 31.45% MA and it jumps right back up the next day. I have a theory that my spa returns are causing aeration. They have a ton of bubbles coming from them.

The returns for the pool don't have this problem. Any ideas? The spa has 3 returns and the pool has 2. I have not yet found a way to turn them off separately. Where could the air be coming from? I have a pipe coming out of the ground the seems to be sucking some air.

Is this the source? I covered with metal tape to test and still had bubbles. Any ideas? Thanks in advance.

 

[JVTrain]

Your TA is marginally high so as you continue to maintain your pH that number will come down. Higher TA results in faster pH rises with aeration. Each time you add acid, your TA will decrease.

As far as the bubbles in your spa returns, many pools with a spa have a blower accessory that intentionally adds air to your returns that feed the spa. Do you have a blower? If so you may be able to bypass or turn it off, except for when you are going to use the spa. A wider shot of all your pool equipment on the pad may help.

 

[Richard320]

What you describe sounds pretty normal. High TA will drive pH up very fast especially with a lot of aeration.

If your system isn't automated, somewhere there should be some three-way valves to select the pump intake and outlet. Look around your pump and filter for any labelled pipes, or start experimenting to see what does what on the valves.

I cut the spa return down to almost nothing and have no suction from the spa under normal conditions. I also have an air intake like yours. I capped it with the lid from a can of spray paint. It reduces the bubbles a huge amount. Spa jets are designed to aerate, so you'll never eliminate all of it, but you can reduce it. As you keep adding acid, you'll notice that it takes less and less acid to get the same effect and you can go longer and longer between additions. That's because the TA goes down some with each pH adjustment and it stays down, even though pH rises again.

If it's really becoming an annoyance, aggressively lower TA. In that case, you'll want maximum aeration - spa blasting fully, pool returns pointing up. Once TA is down below 70, then you can reduce the spa flow and cap the air and set everything back the way it was.