The BB method (no Bicarbonate)

[lusth]

Is it possible to simplify the BBB method even more?

From my days as a chemist, I know that NaHCO3 is a buffering agent, helping to keep the pH of a solution steady. If I am willing to add acid or base every day (like I add bleach every day), do I need to bother with buffering? I ask because I'm having trouble getting both my pH and my Alkalinity correct (Alkalinity is within range, but my pH is a little too high; adding acid hasn't had much effect due to the buffering of the bicarbonate).

Does the bicarbonate do anything critical besides smooth out changes in pH?

 

[chem geek]

Welcome to TFP!

The bicarbonate is not only there as a pH buffer, but also to provide a source of carbonate ions so that the water can be saturated with calcium carbonate to protect plaster/gunite/grout surfaces. I you have a vinyl pool, then this isn't as important.

You can certainly have your Total Alkalinity (TA) lower, down to even 50 ppm if necessary (though usually 70 ppm is sufficient), to have the pH be less likely to rise over time from carbon dioxide outgassing. Even if you have a plaster pool, you can raise the Calcium Hardness (CH) to compensate and get the saturation index near zero. You can use The Pool Calculator to calculate that index and to calculate chemical dosages and side effects. You should also read the Pool School for more information.

If you do end up with a lower TA, but want some more pH buffering, you can use 50 ppm Borates for that purpose, plus other benefits as described here.

By the way, BBB doesn't mean you have to use bleach, baking soda, and borax. It is more of a philosophy of good testing so you know what is going on with your pool and then doing only what is minimally necessary to make the necessary adjustments using inexpensive sources for chemicals. It also makes use of the knowledge of the chlorine/CYA relationship so that chlorine alone can be used not only to sanitize, but to oxidize bather waste keeping the water crystal clear and to prevent algae growth. In my own pool (shown here and here), I only add 12.5% chlorinating liquid twice a week and add a small amount of Muriatic Acid once every month or two. It's a 16,000 gallon pool and now costs around $15 per month in chemicals (chlorinating liquid prices dropped recently at my local pool store ).

Richard

 

[PaulR]

A standalone tub is most often fiberglass, which is the one kind of surface Richard didn't mention. That kind of tub also wants a reasonable calcium saturation index; not as picky as plaster but less forgiving than vinyl.

In my own tub, I use mostly bleach, and some acid to keep the pH under control. Once per fill, I do borates to help with the pH. I'm not sure I've ever used baking soda, as my fill water has a reasonable TA and the tub's level doesn't drop enough between refills to need tweaking.

The canonical hot tub management method is dichlor-then-bleach which has many satisfied adherents.
--paulr

 

[chem geek]

Ah, I didn't notice the OP had a hot tub (it's in the signature, doh!). So please read the Dichlor-then-Bleach link given above and note that to avoid foaming you want a Calcium Hardness (CH) of at least 120 ppm but that you might have this be higher if your TA needs to be very low to attain pH stability. The fact that the pH becomes more stable when the TA is lower is one of the most counter-intuitive things in water chemistry -- TA is both a pH buffer AND a SOURCE of rising pH itself due to increased carbon dioxide outgassing and is especially noticeable in spas when using a hypochlorite source of chlorine such as bleach.