Another Newbie: Seeking Advice on Balancing and Algae Control

[randyt]

Hello,

First time poster here - HELLO. I found this forum a year ago and I really appreciate it! I have learned a lot and I don't go anywhere else for pool advice. I wish the entire internet was a helpful as this site!

I have an algae and balancing problem that has me stumped. Here are my vitals from a Taylor test kit that I bought based on your advice (thank you). I used to live on test strips (, I know).


Pool: In ground gunite/plaster; approximately 25,000 gallons
PH: 7.8 (after 3 gallons of Muriatic Acid applied in past seven days - it was 8.0 last week)
TA: 190 (again after 3 gallons MA in past week - it was 200 before that)
FC: 5.5 ppm (adding approximately 3 gallons of liquid bleach a week since mid-May)
CC: 0 ppm
CYA: >100 - I didn't want to expend the whole chemical bottle to see exactly how high


I have persistent yellowish algae growing along all sides of the pool, from the tile waterline on down about 36 inches. This started in mid-May. I have been in this house for three years. In year 1, after I dismissed the pool guy, use used 3" trichlor tablets exclusively. It kept things very clear... until year 2 in May/June, this yellowish side algae started. I found the TFP site, and determined that my trichlor regime was a problem - crowding out the FC content of my chlorination, and I took the advice to use liquid chlorine exclusively since. I also got the Taylor kit and managed my PH in a range of 7.6 to 7.8. TA was usually 160 - 180. My algae problems were soon gone - I simply added about one gallon of liquid bleach every other day during the summer. My FC remained about 7-8 as a result. Winter is not a problem (this is California).

This summer, right on queue, the yellow algae on the sides returned. I added more frequent liquid chlorine but I noticed that it didn't stay up (say 6-8 ppm) for very long - quickly falling back to about 2 ppm. Then I determined I needed to get my PH down (it has been hovering between 7.8 and 8.0). I added muriatic acid - slowly at first - but it really had no effect. Last week I decided to apply a more aggressive treatment of MA. Based on my numbers, I could target a PH of 7.0 by adding about 2 gallons. 24 hours later, I am at 7.8 (barely any movement). And my TA is virtually unchanged.

I do realize my CYA is a problem, causing me to have to target a very high FC. Last year I got things under control with FC at about 8 ppm, even with 100+ CYA. This year it is not cooperating. I can keep an FC of 8-10 for a day by adding a lot of bleach, but it I suspect my PH being so high is reducing the effectiveness and lifespan of my chlorine. We are in a severe drought in California, and I cannot replace significant amounts of pool water to lower the CYA. Last year I somehow managed to keep PH around 7.6, FC around 8, and my pool was very healthy. This year I am constantly sweeping the sides - every other day, and I just cannot keep up with the algae .

Am I getting distracted by the PH reading now - should I only bombarding with bleach until I get the algae under control? Any advice is whole-heartedly appreciated!

randyt

 

[Texas Splash]

Hi Randy! Welcome to TFP. I suspect you are at a point of no return with that CYA. Actually, it could be much higher than you think. Until you get that down to where you can even read it properly (perhaps under 60-ish), water chemistry is going to be difficult. I have to ask to confirm ... do you have a SWG?

So no sense dumping chemicals in the water only to drain them right out. I would recommend getting the CYA down first, then you can tackle TA, PH, and FC more appropriately.

- - - Updated - - -

We always remind folks who need to drain ... be cautious not to drain too much at once, especially if you have a water table that could "float" or compromise your pool structure.

 

[pooldv]

Welcome to TFP!

With CYA reading 100 at the top of the test scale it could be 200 or even 300. With CYA that high your minimum chlorine level to avoid algae is somewhere above 12 and up to 30. Shock level to get rid of algae will be 40 ppm and possibly approaching up to 100 ppm. Chlorine CYA Chart

Please add your pool info to your signature so we can better help you with your pool, more here, Pool School - Getting Started

 

[randyt]

Thank you Texas Splash. I know the CYA is the culprit, but we cannot fill more than 1" per week in a pool now - this state simply is out of water. So until the heavens open up a bit, I am somewhat constrained. I will try to get the correct reading on CYA and see just how bad it is. I have not added trichlor in a year and last summer I was able to manage things. This year has not been as kind. Randy

 

[Texas Splash]

Totally understand. You can only do what you can. There are some diluted methods of testing CYA for those who are high as yourself. Maybe that will help get you in the ballpark for a decent reading.

As for your other issue (PH and TA high), typically we see if the TA is high, the PH will follow. The standard recommendation is to continue to try and lower the TA. If the PH goes to low, raise a bit through aeration, then continue the TA battle of lowering some more. Eventually you might find that when the TA is closer to 100 or so, the PH might hold its own much better. I didn't see it listed above, but is your plaster new? That of course would contribute to high readings. Just a thought.

 

[randyt]

Thanks again Texas Splash and pooldv. I just added 12 gallons of liquid bleach (targeting FC about 40 ppm). I think I can maintain 10-12 ppm during the coming weeks, and I'll see if this can halt my algae in this wild CYA environment.

I believe this will render it difficult for me to take good PH readings for a while; but for now I would like to see incremental progress on the visible part of the problem.

The plaster is six years old - so not new. There is no SWG. I will look into the diluted method to test CYA also - curious if I really am in the world record range...

I will post back during the week with results. Randy

 

[pooldv]

LOL! World record! I'm trying to remember the highest number I've seen, it was either 400 or 600. Let's not aim for that!

Yes, the PH test is only good up to 10ppm FC, so every time it gets to 9 or 10 test PH and adjust and add more chlorine.

Here are the extended test directions.
Extended Test Kit Directions

Have you looked in to reverse osmosis? People talk about it but I don't recall having seen anyone actually do it.

 

[randyt]

Thanks so much for the extended test kit details, pooldv. That is a great resource.

I am still hoping we get out of this drought one day. I plan on a re-plaster and a few other things down the road, so I will at the same time address the CYA issue - and I'll never use the trichlor pucks again. Until then... well I will be using a lot of bleach. Once we get into Oct/November it all calms down quickly... so three more months of this.

I will keep you posted.

 

[pooldv]

Sounds like a plan. We were in drought for 5ish years or so and got it all back this spring. Lake by us went from 12ish feet down and not full for years to 10 feet over and the dam wide open. Maybe your time is next!

 

[randyt]

Hello, OP here with an update.

Last weekend I followed the advice of several members and the calculator, and I have good news.

With my CYA over 100 and persistent yellow algae, I added 12 gallons of liquid chlorine. My FC was about 40 a couple hours later. I brushed the pool the next night (in the dark it is hard to see how much algae is still adhering to the sides). I did not add another gallon of Chlorine until the next morning (day 3). That night my FC was about 21. There was a very light coating of yellow on the sides, but much less noticeable than what I had been dealing with.

I did nothing on day 4. On day 5 I added another gallon of chlorine. On day 6 (today), I tested the FC and it was 12.5 ppm. I added 1 gallon of chlorine and did a thorough brushing of the entire pool (sides and bottom). There was a light dusting of yellow in places, but it came off really easy, so I assume it was dead.

Six hours later I looked at the pool and it is absolutely spotless - clean with no signs of algae on the sides.

I will target FC at 12 for the rest of the summer. If I have any recurrence, I'll bump back up to 40 ppm for a day or two. In a week or so I will let it go below 10 ppm for a day so I can do a good PH and TA test, then quickly get it back up to 12.

So, for anyone out there with high CYA who is skeptical that 12 gallons of liquid chlorine ($50) will do the job - I can confirm the results with a resounding "yes." Of course you need to use the calculator for your own situation, but for me it was 12 gallons to get the FC up to 40.

I will report back next weekend to confirm the persistent yellow algae on the sides is totally under control.

Thanks for all who helped! Randy

 

[Texas Splash]

Randy, we are pleased to hear your water has cleared and you are thrilled with how your water looks. Now just remember what we always said .... "You must pass all 3 SLAM criteria." If you allow the FC to lower without doing an OCLT and confirming your CC, you run the risk of it returning okay? But I think you know all of that now. Enjoy your clear water, but if anything should come back, use the SLAM approach again and make sure you complete the 3 criteria. Have a great day!