Outbreak Adverted?

[NWCanuck]

Well I must have slacked off a little and I am paying for it now . I have had a clear pool all summer (and have never shocked other than opening day) and Monday night I pulled the solar cover off (it has been cold and wet lately) and the bottom of the pool had a light green film on it which was darker in areas where dirt seems to settle a little thicker. We had some rain over the weekend and I usually vacuum the pool manually every other day but the weather was lousy and we had a lot of rain.

My FC must have dipped <2ppm or else it was the rain because I did have to run the pump to waste to lower the water level for about 5 mins so it was really high (top of skimmer). I think I got lucky though because I did bump the chlorine level to 20ppm right away and vacuumed the pool. I could still see the bottom and everything came off the liner easily. The water was a light tinge of green probably because I stirred it up by vacuuming. This morning (Tuesday) the water was clear but it looked like the algae that were suspended last night while vacuuming settled to the bottom again where dirt usually settles. I vacuumed the pool again and brushed the sides and have been able to maintain shock level at 14-20ppm throughout the day in full sunlight.

My shock level with a CA of 30ppm is 13ppm so am keeping it a little over 13ppm because I have to work throughout the day which is why I am raising it 20ppm and letting it fall to about 15ppm by the time I get home.

Just to make sure I am doing this right should I just keep vacuuming up the fallout which is a smaller and smaller amount each time I vacuum or is there something else I need to do. I am also a little surprised that the Algae that is settling to the bottom of the pool is still a dark green and has not bleached out at 15-20ppm or is two days not enough time yet for this to happen? Also I am not showing any CC and have not since I found the Algae? I am glad I caught this when I did because like I said the water is still clear and looks good after I vacuum until the next morning there is some fallout.

I have had to leave my solar cover off and have gone from a nice 28C down to 22C in just two days of overnight lows around 9C. Lesson learned!

Current as of 09:00PM tonight

FC 14 (added 4 liters 12% to bring it up to 20ppm overnight)
CC 0 (this confuses me because there is Algae although not much)
TC 14
PH 7.4
CH 210
CYA 30
22 Degrees Celsius

Taylor 2006

 

[UnderWaterVanya]

CC does not always rise w/ algae - I'm not sure why.


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[y_not]

It sounds like you are doing good, just keep it up, keep hammering that algae.

A few tips though, to speed you along.....

2 days is typically nothing, some pools not, it all varies, every case is different. Sadly. We're dealing with a bunch of living organisms here. Some people with green swamps have spent 2+ weeks shocking and longer filtering it all out.

Persistence and POP "Pool Owner Patience" is key.
If it's green, it ain't dead yet! Keep killing it.

One concern I do have is that you are over the mustard algae shock level for your CYA, as outlined here. Chem Geek's more detailed CYA chart.
This could potentially cause fading of your liner, but since I'm not an expert on that, I don't want to alarm you. As it isn't that much over, so I'd imagine you'd be OK, as I know there is some leeway room, but I can't say for sure what.
I would think that since it's probably only sitting at 20ppm, 2+ over mustard shock, for a period of let's assume overnight by the time a portion of it gets up from oxidizing your algae and then consuming CL when the sun hits, it's probably not exposed to that high a CL long enough to do any harm. But just to be on the safe side as far as your liner is concerned and until one of our resident experts chimes in, I'd keep it no higher than mustard shock as much as you can.

Make sure you keep brushing and vacuuming, running your pump 24/7 on filter mode. Your pressure should rise with vacuuming and filtering, as it starts grabbing the dead algae.
If not, you need to open up your sand filter, check for channeling in the sand, then clean it. Even if there is none, if it has been in there at least a year, this is recommended every season.
Cleaning and resettling the sand bed.

Make sure to backwash it when the pressure gauge goes about 8psi above it's clean starting pressure. Don't backwash too much, a slightly dirty sand filter does filter better than a squeaky clean one. But they still have to be cleaned and if they're too dirty, they'll never filter right.

Once you have done all this and the algae is dead, to speed things up you can put DE or cellulose fiber media in your sand filter. It's the same process for the latter, you just use much, much less for the same rise in pressure. Either will work, whichever you can get a hold of for a good buy.
Add DE to a Sand Filter

Lastly, when the stuff on the floor is dead, get in and check your pool light, ladder, skimmer, skimmer scupper and any other nooks and crannies you can think of for algae and scrub it with bleach. It likes to hide!

Don't stop shocking until you pass the 3 criteria listed in Pool School.

BTW. Hi Canada!!

 

[NWCanuck]

Thanks for the reply y_not. I was at 20ppm last night and this morning (Wednesday) I am at 17ppm so I will let it fall to my listed shock value of 13ppm. I think I panicked and went over board on the chlorine. The water is clear again this morning and there is no fallout on the bottom of the pool. But having lost 3ppm overnight I will have to keep it at 13ppm until I loose >.5ppm overnight right?

I guess more is not always better and holding it at mustard levels like you said will just be harder on the liner than the algae. Thanks again.

 

[march2012]

Thanks for the reply y_not. I was at 20ppm last night and this morning (Wednesday) I am at 17ppm so I will let it fall to my listed shock value of 13ppm. I think I panicked and went over board on the chlorine. The water is clear again this morning and there is no fallout on the bottom of the pool. But having lost 3ppm overnight I will have to keep it at 13ppm until I loose >.5ppm overnight right?

I guess more is not always better and holding it at mustard levels like you said will just be harder on the liner than the algae. Thanks again.

It might be helpful to keep it a bit above shock level. As the FC gets consumed it will avoid the pool dropping below shock level.

 

[UnderWaterVanya]

Something that may not be clear is that the "shock level" isn't some magical number that is exact and perfect. The recommended levels from the CYA chart here don't quite match those on poolcalculator.com. The other part that may be unclear - Mustard Algae process as defined here is to do NORMAL LEVEL shock until all criteria are passed and THEN raise to MA levels for 24 hours. Additionally you are asked to scrub behind lights, under ladders, etc. You are also asked to take everything that has been near the pool and dump it in for at least one hour at this level.

There is a school of thought that runs straight up to MA level when they have MA - but that's not the normal recommendation. So even if you do think you have MA - if you follow best practices from TFP you would start with normal level shock not MA shock level.

 

[NWCanuck]

Thanks for all the info guys. I have not added any chlorine today and I have had the cover on to keep the remaining heat in. The pool was at 17ppm of FC this morning at 7am. This is the solar covers last season so I am not concerned about the FC levels and damaging the cover as it is 5 years old and toast already.

I have been holding 16.5ppm FC all day (taken at 9pm tonight) so at this point I think I will just let it fall back to normal levels. If I need to use the pool sooner, I will have to leave it uncovered to get rid of some of the chlorine but will probably only uncover to test, vacuum and brush. At this point I am playing a game with warm days and cool nights and trying to stretch my season as long as possible .