Treating Algae with CYA out of whack

[Jerry in AZ]

New to TFP, but I've read the FAQ and will try to abide.

Pool water is clear and blue, but with googles/mask we noted some spots of algae spread throughout the pool, clustered in areas with least sunlight and probably lower water circulation. Determined black alage (smears green on white paper). Decided to attack with brushing and an elevated FC level.

In researching what level of FC was right for this situation here on TFP, I now think my first problem is a CYA problem. Current readings today with the Taylor kit:
TA 130
CH 500
CYA approx. 190 (no usable reading with straight pool water got 190 using 1/2 tap 1/2 pool water and doubling result as suggested in the Taylor book)
pH 7.6
FC 11.8 (got a .4 on combined Cl)

Must I lower CYA before an algae treatment could even be effective?
Pool Math says to drain 58% of my pool - should I go that far?
Is high CYA not the most urgent problem relative to the algae spots?
Regular testing at pool store note CYA ">99" but this is never raised as a concern in need of treatment, why is that the case?

I use dichlor regularly as SWG just won't keep up (high bather load & open agricultural surroundings). From what I read on TFP that is likely the source of CYA as I do not add stabilizer ever. Obviously will stop now that I've found TFP, but need to know what to do to fix this now. As I said pool looks good, but the numbers might suggest a crisis and am looking for some advice.

Thank you.

FC 30
CC 0
pH 7.3 (prior to starting SLAM)
TA 110
CYA 70
CH 380

 

[Nuvene]

Yes you will have to drain some water to lower trade cya. Cya level determines an effective fc level. The higher the cya the more fc you have to maintain in order to prevent algae. Since you are having trouble holding chlorine i would think you need to slam. Once your cya is in range and you slam the pool I would buy be surprised if your swg starts performing properly

 

[Abigail K]

Welcome to TFP!

Replies in red.

New to TFP, but I've read the FAQ and will try to abide.

Pool water is clear and blue, but with googles/mask we noted some spots of algae spread throughout the pool, clustered in areas with least sunlight and probably lower water circulation. Determined black alage (smears green on white paper). Decided to attack with brushing and an elevated FC level.

In researching what level of FC was right for this situation here on TFP, I now think my first problem is a CYA problem. Yes. Current readings today with the Taylor kit:
TA 130
CH 500
CYA approx. 190 (no usable reading with straight pool water got 190 using 1/2 tap 1/2 pool water and doubling result as suggested in the Taylor book)
pH 7.6
FC 11.8 (got a .4 on combined Cl) Switch to a 10ml sample. Each drop counts as 0.5ppm and it is precise enough.

Must I lower CYA before an algae treatment could even be effective? Technically, no. Treating algae is about the ratio of FC to CYA, and brushing. However, the amount (and costs) of bleach required to SLAM at that CYA level is relatively high. Taking your location into account, I would advise lowering your CYA level either by a drain/refill, or an RO service.
Pool Math says to drain 58% of my pool - should I go that far? Someone else would answer this question.
Is high CYA not the most urgent problem relative to the algae spots? It is.
Regular testing at pool store note CYA ">99" but this is never raised as a concern in need of treatment, why is that the case? Pool stores don't understand the FC/CYA relationship.

I use dichlor regularly as SWG just won't keep up (high bather load & open agricultural surroundings). SWG unable to keep up may also be due to incorrect FC/CYA ratio. From what I read on TFP that is likely the source of CYA as I do not add stabilizer ever. That is correct. Obviously will stop now that I've found TFP, but need to know what to do to fix this now. As I said pool looks good, but the numbers might suggest a crisis and am looking for some advice. Lower CYA and SLAM.

Thank you.

Also, I would advise you to read ABCs of pool water chemistry if you haven't already done so.

 

[GoGi]

Jerry,

I am also battling my second algae bloom in two years. The first time I was pool-stored and I ended up wasting a lot of money and time mainly due to the high CYA (and the shock they sold me kept raising the CYA.) This time around, I almost followed the pool-store method of BurnOut 35 to shock but after the first application (and $140+), I decided to research some other alternative: and hence my relationship with TFP was born. My CYA was at 120 and PoolMath recommended I drain about 65%. I ended up draining close to 45% and my CYA dropped to 70. Meanwhile, bleach SLAMing has done its trick and in about 4 days since starting, I can see the bottom drain (albeit cloudy water.) In short, go ahead and drain some water and lower you CYA. I read my water meter before refilling and after refilling and given our current water rates, 45% will cost me about $72. This is way cheaper than I would have been buying chemicals for!

 

[SunnyOptimism]

Only fast way to lower CYA is drain and refill. My pool was 150 and I drained and diluted it down to 60 now. SLAMing at 60 CYA uses A LOT less chlorine and my SWG runs at a much lower setting ( 40%) now.

Pool stores test CYA but they don't tell you that a CYA greater than 90 is a problem because they can't profit from it. Major pool store chains are not dumb, they know that properly stabilized and balanced water is easily maintained with bleach as the source of chlorine. They ignore this because doing so allows them to sell all kinds of "dressed up" chemicals at marked up prices (aka, profit).

Think about it this way- pool store and pool service company business models absolutely depend on you having bad pool water as that is the only way they can make high profit margin sales or perform expensive, off-contract service calls. So for them, measuring a CYA of 99 and telling you it's "OK" is simply their way of making sure you'll be back on line in a couple of days buying more shock, floc, baquacil, PhosFree, etc, etc.


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[Jerry in AZ]

I had an algae outbreak that was primarily on pool surfaces and in shadier areas (or possibly lower water circulation areas) so I have been SLAMing for four days. Water is now crystal clear and CC is 0, so I'm 2 of the 3 criteria to stop the SLAM, but I still have some dark streaks on the bottom of the pool that look like Algae to me. My questions:

Should I bother with the OCLT at this point?
Is it possible what I am seeing is dead and just brushing, filtering, and time will clear it up? (Would the OCLT help test tell me this?)
Should I keep SLAMing and brushing?
Should I go up to mustard algae level?

I'm not sure exactly what type of algae I had, but it was primarily on surfaces, not floating in the water. It looked green to me, but maybe had some yellow in it. The pebble texture of the pool makes it tough to really see.

Any advice is appreciated.

Thank you.

 

[tim5055]

Generally if you see something that appears to be algae, you do not pass the "water is clear" test. But, you say you are not sure if it is, so I would say yes - go ahead with the OCLT. If you have a pool light you might even give the area a brush after you take the first a reading after dark. If it's a patch of algae protected by biofilm the brushing should get a good interaction with the algae.

Any possibility it may be metal staining? Have you us any metal based algecides?

 

[zea3]

I had an algae outbreak that was primarily on pool surfaces and in shadier areas (or possibly lower water circulation areas) so I have been SLAMing for four days. Water is now crystal clear and CC is 0, so I'm 2 of the 3 criteria to stop the SLAM, but I still have some dark streaks on the bottom of the pool that look like Algae to me. My questions:

Should I bother with the OCLT at this point?
Is it possible what I am seeing is dead and just brushing, filtering, and time will clear it up? (Would the OCLT help test tell me this?)
Should I keep SLAMing and brushing?
Should I go up to mustard algae level?


I'm not sure exactly what type of algae I had, but it was primarily on surfaces, not floating in the water. It looked green to me, but maybe had some yellow in it. The pebble texture of the pool makes it tough to really see.

Any advice is appreciated.

Thank you.

Yes do an OCLT. That is one of the criteria for passing the SLAM. It may just be accumulated debris that needs to be vacuumed up. Vacuum the pool and do the OCLT. Your results will tell us what to do from there.

 

[Casey]

If you have what appears to be streaking algae on the floor, I'd keep SLAMing and brushing the pool. Doing an OCLT will definitely tell you and us if something is still consuming the chlorine.