Plaster is like Sandpaper

[chem geek]

My TA was around 60 so that is why I added baking soda. Low TA and aeration is what caused erosion of my plaster so I am worried about that and was shooting for a mid-range level.

It is not just low TA and aeration that can dissolve plaster, but also low Calcium Hardness (CH) and low pH. It is the combination that you want to saturate the water with calcium carbonate. So you can readily have a lower TA level of 60 or 70 ppm if you don't lower the pH as much and you raise your CH level. A higher TA will have the pH tend to rise faster. I'd shoot for 70 ppm and raise your CH as needed. Let's say you plan to keep your pH in the 7.6 to 7.8 range and that you have your CYA level at 80 ppm (to minimize chlorine loss so you can turn down your SWG on-time) and have a minimum FC target of 4 ppm. Assuming 3000 ppm salt, you could raise your CH to 500 ppm to have a saturation index of -0.2 at pH 7.6 and 0.0 at pH 7.8 which should be fine (you could have your CH at 400 ppm and probably be OK since your pH tends to stay towards the higher side).

What are the Borates for, to lower my TA?

The 50 ppm Borates are for additional pH buffering that should slow down the rate of pH rise and also prevent scaling in the SWG cell.

My pH generally goes from 7.6 to 8.0 overnight.

This is probably a combination of your TA being too high and having the short pipe runs not fully dissolving chlorine gas. The use of 50 ppm Borates will also slow down this rise though won't change the amount of acid you need to add. Having your CYA level at 80 ppm will help because it will protect chlorine from sunlight more even with the FC higher to maintain a 5% FC/CYA ratio (i.e. 4 ppm FC with 80 ppm CYA). Losing less chlorine to sunlight means you should be able to lower your SWG on-time and that will reduce the rate of pH rise since there will be less aeration of the water from the hydrogen gas bubbles and less chlorine gas that escapes.

I do have short pipe runs. The returns are aimed so that it barely ripples the surface of the water. What is the correct way to aim the returns? Should I aim all 5 of them down?

I would point the returns that are closest to the pump downwards or diagonally downwards (depending on the type of flow you want). You'll probably need to keep some returns pointed so that you get some surface water motion to be able to move debris to the skimmer.

[Mikes Pool]

Thank you Chem Geek. I think you have illustrated how each pool (mine, for example)is different and how the pool store's cookie-cutter approach doesn't work for all pools.

I have followed your advice up to this point;

The TA mysteriously went down to 70. This is after adding baking soda 2 weeks ago to bring it up to 90. I'm glad that it went down on it's own as I understand the process in attempting to lower it. I just hope it doesn't keep dropping.

I increased the CH to 425 from 275.

I adjusted a few of my jets and changed the pump run-time from 14 hours a day to 9 hours a day. I also increased the chlorine output on my SWCG to compensate for the reduced run time. Will this cause an increase in gas bubbles?

Today the pH was 7.8 and the FC was 5.4. CC was 0.0 My CYA is still at 70 but I will bring that up.

The one thing I'm not sure of is the Borates. What is it and with what do you increase it and measure it?

I want to thank you again for taking the time to help me with this and to be a more educated and trouble free pool owner.

[CarlD]

I can answer that last one:
You add borates by adding ordinary 20 Mule Team Borax, which we also recommend first for increasing pH (so you have to add acid to control pH).
There are borate test strips which are about the only test strips we recommend. Higher borates inhibit algae and make the water feel softer.

[chem geek]

You can add borates by adding a combination (added separately in split doses) of borax and acid or you can buy boric acid and add that instead.

[Mikes Pool]

To all of the Pool Forum experts:

I want to give you all a big thank you. For the first time this year I feel like I finally have my pool water where it needs to be and more or less trouble free. Besides the eroded plaster, my big issue was the pH rising constantly. The pH still rises and I still have to add acid but by following everyone's advice on this forum the frequency of adding acid has been reduced by about 2/3rds. The plaster I will deal with at a later date.

The advice from Chem Geek to raise my CH to 500 and to lower my TA to 60 is contrary to what I would have heard from any pool store or any swimming pool publications, but that is what my pool needed.

My first post on this forum was almost 2 months ago. If there is any bit of advice I can give to new subscribers it would be to have patience and to do exactly what you are told to do by the people who are trying to help you. There is no magic bullet. It takes time, patience, and persistence. With everything I have learned about my pool this year I am confident that I will have no trouble maintaining my pool in the future.

Happy Swimming!

[Watermom]

Thank you, Mike, for the nice post! Glad you had a good summer and were able to enjoy your pool!