High Alkalinity, medium pH, High Chlorine

Problems relating to pH and total alkalinity. Increase ph, increase TA. Reduce pH, reduce TA. pH chemistry advice and techniques.

High Alkalinity, medium pH, High Chlorine

Postby njpool » Thu 27 Apr, 2006 13:20

I bought a house last fall with a 20X40 inground vinyl pool. The setup includes a system similar to the Pool Wizard (i.e. competing product) plus an inline chlorine feeder. When I used a test strip in fall (before closing the pool), the results showed a TA of about 250, plus a high pH (>7.8) and a free Cl of 10. In prep for closing, I shut down the Cl feeder to get the Cl lower, plus added pH reducer (both dry acid & muriatic acid). I got the pH down around 7.8, but Cl readings were still near 10, plus TA really didn't go down. Through all this time, water was clear & seemed fine (didn't actually swim since it was too cold).

Fast forward to this month. Pool was opened & besides normal dirt, water was clear. Opened up the Cl feeder to shock pool. Cl readings are around 10, with pH around 7.6-7.8. but TA around 250. Just started adding some muriatic acid using the recommended 'pooling' method.

Just to make sure, I am have switched to using chemicals to test the water, but I am waiting for the chemicals to do their thing first. I also will need to run at high Cl when I replace the silver/copper cartridge, as recommended by the manufacturer.

Question is, am I over-worried about the TA? Should I work to reduce Cl levels as well? It never seemed to come down last fall, even after shutting down & clearing the feeder. Other posts note that TA may not be as big a deal if pH is stable & water is clear. What are acceptable highs for TA & Cl?

BTW, a great resource!!!!
njpool
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Total alkalinity problem

Postby Pool Helper » Thu 27 Apr, 2006 14:45

Welcome to the forums.
The values you have given indicate a constant high total alk and a high pH, which is to be expected from the total alk level. Also the chlorine level seems way too high.

The problems as I see them are:
- high TA and pH result in inactive chlorine, making disinfection slow
- high TA and pH can cause scale
- high TA and pH can shorten the lifespan of the minerals in the Pool Wizard, Nature2 and other mineral systems
- a chlorine value of 10ppm is extremely high, wasting chlorine and defeating the purpose of using the Nature2

The possible solutions:
- ignore total alkalinity but keep the pH at 7.0-7.2 (7.4 tops) to offset the effects of the high total alk
- when adding pH reducer use the "pooling" method every time
- turn off the feeder to allow the free chlorine level to drop to 0.5ppm and maintain it below 1.0ppm by keeping the feeder turned way down
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