Tabs usually require pH Rise and Alk Increaser.

Salt cells are generally using acid which lowers pH.

Scott

So if I am using trichlor tabs, can I safely assume I will rarely, if ever, need to add acid to the pool, but instead plan on adding soda ash, or does one still get high ph issues even with chlorine tabs?

Yes, in the long run. Bear in mind that a full plaster cure will take several months. Curing often cause bounces pH to the high side, even with the use of tabs. Even though the plaster has hardened in a couple weeks, curing takes time.

Scott

"So if I am using trichlor tabs, can I safely assume I will rarely, if ever, need to add acid to the pool, but instead plan on adding soda ash, or does one still get high ph issues even with chlorine tabs?"

Unless you use an exorbitant amount of tablets (commercial pools) chances are you will never have to raise the pH in a plaster pool, unless you added something that lowered it past your set point.

In a vinyl or fiberglass pool, you will have a low pH because the composition of the vessel is relatively inert. A plaster pool, even old ones you will notice a constant increase in pH over the life of the vessel, even while using an acidic chlorine.

In addition to dense ash (pH Rise), Sodium bicarbonate, aka baking soda aka Alkalinity Increaser should be used as a buffer that slows the rate at which pH moves due to tabs, sun and rain's effects.

The rate a plaster pool can raise pH slows with time. I have not seen it effect plaster that is older than 5 years and up, so pH increaser usage and alk increaser usage will be about equal to an equivalent liner or fiberglass pool.

Scott

None of my customers using erosion feeders have to adjust the ph of their plaster pools if they keep up the bicarb level. Alot of them have 40kgal pool ozonators feeding the spa. They also typically have 8+ ph makeup water but I don't think that makes a significant difference.

Don't know about liner or fiberglass pools.

We have a chlorine pool, which is almost a year old. I test every week or so and was adding about 1 - 2 quarts of acid every time I tested for a while. Here lately everything has been perfect and all we add is the tablets, plus shock whenever necessary. We do add algaecide once a week. We still have several bottles of acid, which our builder gave us with the pool startup.