Algae mitigation during extended CYA dilution

[MBPooldiy]

Still a TFP newbie but learning tons from the wonderful contributors on this site. Moved here to Phoenix about a year ago and continued the services of a pool service who had been managing the pool for the previous owner. We recently took over the pool maintenance after being frustrated by the expectation that when CYA gets too high, we will “simply” drain the pool (or pay to have it done), plus calcium deposits continually forming at the water line. Living in the drought-stricken desert, I am reluctant to do a massive pool drain and/or pay almost annually for RO filtration and tile cleaning (in addition to paying for the weekly pool service—however that part has now been addressed…)

I am hoping that my CYA will gradually decline by sticking with liquid chlorine and doing a weekly heavy backwash, along with the seasonal rains. As of week 1, it appears that CYA is down slightly!! I know this will take a while and would like to add an extra layer of insurance to minimize algae formation while I’m waiting for the CYA to drop. I would also like to avoid needing to add huge amounts of liquid chlorine because I will be doing this manually for a while. I have been adding 1 to 2 quarts of 10% LC daily. Although my CC remains 0 with daily testing, I do see faint green clouds of algae stirred up when I brush if I miss just 1 day of brushing which is why I have an interest in determining if there is an optimal way to slow the algae as much as possible until CYA reaches a manageable level.

I gather from all of the postings that I’ve seen so far that the most common (temporary) options for mitigating algae are to use a polyquat algaecide or a non-metallic phosphate remover like Orenda PR-10000. What I’m trying to understand at this point is—which of these might be preferable as a first step? According to the pool store, my phosphates are too high. (They measured 463ppb and say the maximum should be 100.) I have a test kit on order to test my own phosphate level. I was thinking if my test shows that amount or higher perhaps try a small amount of the phosphate remover, confirm by retest how much the phosphates are reduced and then see if I notice the algae formation slowing down. Then decide whether or not the weekly algaecide is also needed. I was thinking that if the phosphate remover helps, that would be a more infrequent expense than the algaecide which might need to be added weekly for the summer.

Does this make sense? If not I would appreciate being pointed to any other pertinent readings.

BTW I did also consider converting to SWG but that is currently a non-starter due to our property layout which would make it difficult to backwash or drain the pool without harming our landscaping.

Latest test results:
FC 4.5
CC 0
pH 7.8
TA (CYA adjusted) 82
CH 500
CYA 195 (down from 210 last week)
Salt 610
CSI -.27
OCLT loss .5

Thanks!

 

[Rancho Cost-a-Lotta]

You have algae. You need to complete the SLAM Process, but your CYA is 195 which makes the SLAM and future maintenance nearly impossible. You're in a tough spot.

I gather from all of the postings that I’ve seen so far that the most common (temporary) options for mitigating algae are to use a polyquat algaecide or a non-metallic phosphate remover like Orenda PR-10000. What I’m trying to understand at this point is—which of these might be preferable as a first step? According to the pool store, my phosphates are too high. (They measured 463ppb and say the maximum should be 100.) I have a test kit on order to test my own phosphate level.

Algae remover will help prevent algae, but it doesn't do a good job of killing it. Phosphate removers are acceptable to use for HIGH phosphate levels, but 463 ppb (0.443 ppm) is low and not a concern. Most of us don't worry about phosphates.

BTW I did also consider converting to SWG but that is currently a non-starter due to our property layout which would make it difficult to backwash or drain the pool without harming our landscaping.

I understand the challenge of draining/backwashing, but I don't understand what bearing a SWG would have on that challenge . Get a SWG.

You made the right decision in getting rid of the pool guy and keeping solid forms of chlorine out of the pool. Your challenge now is getting your CYA level down to 50-60 ppm or even 80 ppm with a SWG. Your means of lowering CYA with minor water exchanges will work, but it's highly inefficient and will take some time. CYA levels do drop slowly as a result of high water temps and UV degradation, which will help a bit. If you go this route, you'll have to deal with the algae. It won't go away without a SLAM. You can add 4-5 ppm of liquid chlorine daily to help stabilize things.

If it were my pool, I would take the hit for RO service and move on. You have softened fill water and if you avoid solid forms of chlorine, no rising CYA levels. You shouldn't have to do the RO or exchange water again. You'll get to enjoy the pool during the hottest part of the swim season and won't have to share the water with algae.

 

[MBPooldiy]

Thanks, I appreciate the way you presented that suggestion. It is tempting to just start over with the RO treatment. Maybe in a few weeks when I get impatient with how slowly the CYA is dropping and tired of dealing with the algae. The concern with the SWG is that many plants and trees are sensitive to water with higher salt content, either due to being irrigated by it or build up in the soil over time which will prevent anything from growing there. It's one of the reasons that we use potassium in our water softener instead of sodium, so I don't have to worry about using that water on my plants. (Gardening is a major hobby and now managing my pool has become a second hobby.) I already know that the existing landscape can tolerate the chlorine pool water and I believe that chlorine in the pool water dissipates rather than building up in the soil. It's not to say we won't eventually move to SWG but it will probably involve planning out and installing improved backwash plumbing that will be compatible with the existing and future plants. So it's appealing as a longer term option but it wouldn't be plug and play and too many other projects to deal with this year.

 

[Rancho Cost-a-Lotta]

The concern with the SWG is that many plants and trees are sensitive to water with higher salt content, either due to being irrigated by it or build up in the soil over time which will prevent anything from growing there.

That makes sense.

Just realize that "salt" pool levels range between 3000-4000 ppm, about the 1/10th the concentration of ocean water. Even "non-salt" pools can have salt concentrations of 2000-3000 ppm as a result of byproducts left behind by other forms of chlorine (sodium hypochlorite) and other chemicals. You'll know better than me what that means in terms of your plants.

Let us know when we can help. In the meantime, arm yourself with knowledge. Check out Pool School and TFP Wiki (link below).

Best of luck!

 

[mknauss]

RO companies will not perform the service on a pool with algae. It will foul their system.

Do an exchange. The water is not 'wasted'. It goes back into the system through the waste water system.