Hi. I have a 20,000 gallon in ground pool with a cartridge filter that always had good chlorine (and other) readings for years with tabs in a floater. My pump (3/4 hp variable speed that always ran on the low speed) went out and I got a new 1 hp pump (single speed). Ever since then (and I mean almost immediately) I cannot keep chlorine in the pool. Nothing changed but the pump. I run it the same number of hours per day (6-8) as I did before. There is no free or total chlorine being maintained. I now put a gallon of 8% bleach in every day and after 24 hours it shows nothing. Initially I was using the floater with tabs and nothing. I added another floater with tabs and nothing. I use phosfree and the phosphorus reading is very low so that is not it. I asked a guy at the pool store if too large a pump could cause this and he said yes. I asked another and he said no. The circulation is clearly much greater than it used to be. I am at a loss. Any thoughts? Thanks!
Problem since getting new pump
- Thread starter CCC
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Welcome to TFP.
While your pump was down you most likely developed algae. You need to read & follow the shock process. If you don't have a good test kit, that is the first thing you need. With the FAS-DPD test you can run the OCLT to be sure but you need to start the shock process right away.
While your pump was down you most likely developed algae. You need to read & follow the shock process. If you don't have a good test kit, that is the first thing you need. With the FAS-DPD test you can run the OCLT to be sure but you need to start the shock process right away.
Welcome to TFP 
Ditto to what Bama said. It's not the pump and it's not phosphates (phosphate reducers are nice way for pool store to make extra cash and it is rarely ever needed), but likely organcis have gotten their start while your pump was down (whether visible or not). 1 Gallon of 8% in a 20k gal pool is only 4ppm FC and likely got used up by organics within an hour after adding it. You need a good reliable test kit and lot's more bleach to shock the pool.
Link to pool school is on top right of this page or my signature.
Good luck
Ditto to what Bama said. It's not the pump and it's not phosphates (phosphate reducers are nice way for pool store to make extra cash and it is rarely ever needed), but likely organcis have gotten their start while your pump was down (whether visible or not). 1 Gallon of 8% in a 20k gal pool is only 4ppm FC and likely got used up by organics within an hour after adding it. You need a good reliable test kit and lot's more bleach to shock the pool.
Link to pool school is on top right of this page or my signature.
Good luck
Thanks for the replies. I attempted to do your shock treatment a while back but did not have that good of a test kit. I will get one and try again. If everything is as it should be, how much bleach and how often should I expect to have to add it? It is still around 100 degrees here (Texas) but my pool is screened in so that cuts back on some UV. I had an unfortunate event with the CYA. While troubleshooting the chlorine problem I tested the CYA with a test strip and it showed no reading. I added some and still nothing. I added a little more and still nothing. I then realized my test strip was "dead" and so I actually have a reading a little over 100 now. All my readings from the pool store prior to the pump going out for the CYA were good so that was not the cause of the initial problem. I am looking into a company to come do a reverse osmosis treatment. The water is very expensive here and we are under water restrictions. Thanks again!
If your CYA level is 100 or greater, your chlorine is virtually ineffective. The only cure for high CYA is water replacement. Assuming the level is 100ppm, to get your CYA level down to the recommended level of 50 (30-50 recommended) you would need to replace 1/2 your water.
Based on thechlorine/cya chart , you need a shock level of 39ppm FC ,which going from zero to this level would require 1,618 oz of 6% bleach! And, this would need to be added to several times throughout the evening to keep the level up, especially during the inital hours of shocking.
Based on thechlorine/cya chart , you need a shock level of 39ppm FC ,which going from zero to this level would require 1,618 oz of 6% bleach! And, this would need to be added to several times throughout the evening to keep the level up, especially during the inital hours of shocking.
Most places you cannot go and get a good test kit. It needs to be ordered. You will need to get the TF100 XL because you will be doing a LOT of testing to get your pool right. It CAN be done! 
High CYA will cause you a LOT of problems. Until you get it down (drain water) you will have an uphill battle with your chlorine. :grrrr:
Good luck and keep us updated!
Kim
High CYA will cause you a LOT of problems. Until you get it down (drain water) you will have an uphill battle with your chlorine. :grrrr:
Good luck and keep us updated!
Kim
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