Cecil Posted June 2, 2020 Report Share Posted June 2, 2020 (edited) I have a Michael Phelps Swim Spa Signature Model that is 2,325 gallons. Just drained and refilled with untreated well water and filtered out the precipitated iron with a couple of changes of filters. My problem is getting the Ph in the range that is optimum for the Chlorine. I test the PH (after aeration and liberation of CO2 ) at least at 8.0 (test kit only goes up to 8.0 so it may be about 8.4 or 8.5, which is common in my fish rearing aquaculture systems. Anyway, an acid demand test doesn't even come close to the amount of Muriatic Acid to add to bring the Ph down to 7.4 to 7.6, I'm assuming because my Ph is above the maximum Ph of the test kit? As due to the logrithmic Ph scale 8.4 or 8.5 is 4 to 5 times the base of 8.0. Additionally the total alkalinity is about 350 mg/l which as we know acts as a buffer fighting Ph change. Total hardness is quite hard in the 500 plus range. When I do get the Ph down where it should be it bounces right back again by the next day no doubt due to the high alkalinity and aeration.But once I do get enough Muriatic Acid in the water to bring the Ph to the right level to stay there the Total Alkalinity is dangerously low. So the remedy for bringing the Ph back up is to add Sodium Bicarbonate (Backing Soda). You'll never guess what that does to the Ph. Thoughts? Edited June 2, 2020 by Cecil spelling error Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted June 3, 2020 Report Share Posted June 3, 2020 Define "dangerously low". Below 50ppm? Quote Link to comment Share on other sites More sharing options...
Cecil Posted June 3, 2020 Author Report Share Posted June 3, 2020 Yes! Quote Link to comment Share on other sites More sharing options...
Cecil Posted June 3, 2020 Author Report Share Posted June 3, 2020 I see now there are online apps you can plug in all the water parameters and it will tell you how much acid to add. Wasn't aware of that. Will give it a try. Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted June 3, 2020 Report Share Posted June 3, 2020 Give it some time to balance out. Alkalinity that low will drag your ph down over time. Close your air intake valves when not in use to slow aeration. Quote Link to comment Share on other sites More sharing options...
Cecil Posted June 3, 2020 Author Report Share Posted June 3, 2020 17 hours ago, RDspaguy said: Give it some time to balance out. Alkalinity that low will drag your ph down over time. Close your air intake valves when not in use to slow aeration. Thanks but the pool automatically runs (cycles) twice a day. Quote Link to comment Share on other sites More sharing options...
Cecil Posted June 3, 2020 Author Report Share Posted June 3, 2020 I was able to get the water down to 7.2 PH after adding muriatic acid 4 times and alkalinity isn't too low at 90 mg/l. Then added my chlorine. Should be interesting to see if the Ph jumps back up overnight which has been an issue in the past. Thank you for the suggestions! Quote Link to comment Share on other sites More sharing options...
Cecil Posted June 4, 2020 Author Report Share Posted June 4, 2020 (edited) Sure enough Ph is back up to 8.0 or more. If true to form I will go through this several times until the Ph is stable where I want it but the alkalinity will be low. I envy those of you that don't have high Ph in their supply water. Edited June 4, 2020 by Cecil added sentence Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted June 4, 2020 Report Share Posted June 4, 2020 I have well water with high everything but do not experience these issues. Worry about ph, not alkalinity. The risk of low alkalinity is sudden drastic ph drop, which would be a good thing in your case. 7.8 is fine. You might try borates as a ph stabilizer. Quote Link to comment Share on other sites More sharing options...
Cecil Posted June 13, 2020 Author Report Share Posted June 13, 2020 I'm still having the Ph bounce back to at least 8.0 (highest Ph goes with the color test) after several applications of Muriatic acid to get the Ph down. Acid demand tests show much less acid to add than I have added. I know my high alkalinity and hardness will buffer Ph changes and cause it to bounce back but this is ridiculous. I'm thinking perhaps: 1.The reagents are old or heat damaged and hence Ph reading is not accurate. Do the reagents used for ph get damaged by the heat of the swim spa room? 2. The Muriatic acid is somehow not at full strength via age? Am considering getting a higher quality water quality test kit. Quote Link to comment Share on other sites More sharing options...
RDspaguy Posted June 14, 2020 Report Share Posted June 14, 2020 What type of chlorine do you use? Liquid has a high ph, dichlor is nearly neutral, tablets are low. Perhaps you should try tablets. Just tie off your floater away from the skimmer or it will speed up equipment damage. Quote Link to comment Share on other sites More sharing options...
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