Trouble Getting Chlorine Levels up in a Salt Water Pool

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T

TheDuke

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Jun 16, 2013
23
Massachusetts
i recently purchased a home with an inground, gunite pool that was originally bromine. This season, I converted my pool to salt water. I'm using a Hayward cartridge filter and a Hayward salt generator with a T-15 cell. I have been having issues getting my chlorine levels up. I had my SWG set to 55% and recently just raised it to 70%. I'm located in New England and we recently have had 90 plus degree days. I just had my water tested and my readings are as follows:

P.H. = 7.6
Free Chlorine = .5 ppm
Total Chlorine = .5 ppm
Stabilizer = 30 ppm
Total Alkalinity = 100 ppm
Calcium Hardness = 340 ppm
Salt = 3200 (reading from the SWG)
Saturation Index = .12

My pool size is approximately 25,000 to 30,000 gallons. The employees form the pool stores are not sure what the problem might be. I'm not sure if there is something chemically that's causing this problem or could it be the SWG? Any advice is appreciated.

Jason
 
Hi, welcome to TFP! I have a few questions for you. What method did you use to convert the pool from bromine to salt water? Did the shop that sold you the SWG know it had been a bromine pool? Have you tested to see if you still have bromine in the water? Have you pulled a sample at the pool return while the SWG is producing chlorine and had it tested?

Your CYA is too low for a SWG pool. It should be at 70ppm, however that may not be the real problem in this case.
 
Most SWG require a level of 60 to 80 of cya in order to function properly and help protect the FC they generate. I suggest you raise your FC level with bleach per the pool calculator in pool school as you adjust your cya level. Welcome to TFP. As zea said........your conversion method could be your problem.
 
I had the pool converted by a pool service company and "yes" I told them that the pool was bromine. They were the company that actually closed the pool when it was bromine last season. When they opened the pool this season and during the conversion, it was discovered that the my cover failed and the pool was filled with water from the elemnets throughout the winter (rain, snow, ect). So, what they had me do, was to shock and use the water that was already in the pool. No, I have not had the water tested for the presence of bromine, could this be the problem?? Haven't taken a sample directly from the return and had it tested. i Just added two gallons of liquid "Pool Basics" stabilizer. Had some algae, so i brushed and added 2 1/2 gallons of liquid shock as well.

Any thoughts of the possible problems?? Am I on the right track??
 
There is a saying, "once a bromine pool always a bromine pool". That has to do with the way bromine works. Bromine is used as a primary sanitizer activated by the addition of chlorine. Bromine lasts in the water a good long time and oxidizes out slowly. For more information on this you can read If you started using chlorine instead of bromine. The most efficient way to convert to chlorine is to replace 90-100% of the water. I don't know if a filter medium change is also required but I am sure someone who does know will come along soon to let us know.

Your pool guy may have been unfamiliar with the way bromine works, but when he had you "shock" the pool all that did was re-activate the bromine.
 
There are two possibilities I can think of. If nearly all of the bromine is gone (which seems unlikely) then you need to SLAM the pool and then raise the CYA level. Having CYA as low as you have it now causes problems for a typical SWG, and now that FC has gotten that low you need to SLAM to make sure you don't have a low level algae problem.

If there is still bromine (which seems likely) then everything might work in principal. The SWG will produce chlorine, which will reactivate the bromine. However, Hayward explicitly recommends against using their SWGs in a bromine pool. Also, bromine can not be stabilized against sunlight loses to the same extent that chlorine can, so it is impossible to get the bromine loss rate down as low as chlorine loss is at higher CYA levels, so you may well need a larger SWG to keep up. Putting aside Haywards recommendation for a moment, which I don't know the exact reason for, you need to SLAM the pool to insure things are good, turn up the SWG percentage, and manually supplement the SWG with additional chlorine when the temperatures are as hotter than usual.
 
TheDuke said:
Thanks Jason, will do! Just out of curiosity, why would the bromine effect the chlorine levels or the SWG?
Click to expand...
I'm guessing it is because the bromine combines with chlorine the chlorine is consumed much more quickly than it would be consumed in a chlorine only pool. SWGs are designed to deliver small, consistent doses of chlorine and likely would not be able to keep up with the oxidation demands of a Bromine pool unless you moved up to a much larger cell.
 

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Thanks Zea, went to the pool store today to try to get a bromine reading and of course the kid at the counter had no idea how to test for it! So, I found a strip test that tested for bromine (the color chart and the strip for bromine was shared with chlorine?). The test resulted indicated zero for bromine / chlorine. Do you guys think that this is somewhat reliable to determine whether bromine still exists in the pool? is there another method that is more reliable i should use to test for bromine?

Thanks!
 
The test most pool stores use for bromine is the same one they use for chlorine. Here is a link to show what the test looks like. If the strips read bromine only, try testing 1/2 hour after adding chlorine.

If you continue to get 0 chlorine/bromine, go ahead and conduct the slam process on your pool.
 
The test strip that i use looks it test for total chlorine / bromine. i added four gallons of liquid "shock' and tested the water about 2 hours later. The test strip indicated about a 5 in the total chlorine/bromine portion. So, how do i know if the reading is indicating the presence of chlorine or bromine???
 
The problem with test strip is they are not accurate. They, to my knowledge, cannot detect if they are coming from CL or BR.

You need an accurate, reagent based test result to know the difference.
 
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