Great News albeit surprising news for my 3 week unattended pool!

[setsailsoon]

Folks,

So you may have seen my posts back in December where I had to leave for 3 weeks. I raised my FC level to 16.5 ppm and added acid to get my ph back to 7.4 before I left. I also put 5 Trichlor tablets in the inline chlorinator and set it to the setting that normally applies 1 tablet per week. The pump runs 10 hr/day and I turned the solar heater off plus I left the suction pool cleaner hooked up and set to stay only on the bottom. I was pretty concerned I'd have a green pool (meaning green water not just algae on the walls) when I got back. I was able to view the pool on a security camera while out of state and to my surprise the pool color stayed clear and the walls only built up a very thin layer of green algae on the walls that were in afternoon sun. And get this. The pool chemistry is almost perfect! (see my test results below). So I cleaned the filter (not especially dirty but it did have some green algae at the bottom. Most of the media was white or barely off white.

I was expecting the worst and I'm guessing the explanation is that my FC stayed high enough to keep the suspended live algae in check and as the individual cells died they clumped then got trapped in the filter. And I guess the pool would go green completely if I let the FC drop far enough. I plan to scrub in the morning and filter during the day then go back to my normal TFP routine as the FC drops to normal levels for my low CYA level. And I'm thrilled that the CYA level did increase about to levels predicted by the Pool Calculator. The only thing I can't really explain is why the algae on the walls stays alive (or at least the contained chlorophyll stays in the cells).

Any comments?

Date	TA	CYA	FC	CC	CH	PH	Actions/Observations
15-Dec-15	70	20	5	0	300	7.5	Added 4 oz Muratic early morning, tests 5 hrs later
16-Dec-15							Added 192 oz 10% Cl
17-Dec-15			16.5			8.4	Cleaned Filter, Addded 16 oz muriatic, 40 oz trichlor, Chlorinator 1.5, noon ph 7.4
18-Dec-15							Gone but pool water clear
19-Dec-15							Gone but pool water clear
20-Dec-15							Gone but pool water clear
21-Dec-15							Gone but pool water clear
22-Dec-15							Gone but pool water clear
23-Dec-15							Gone but pool water clear
24-Dec-15							Gone but pool water clear
25-Dec-15							Gone but pool water clear
26-Dec-15							Gone but pool water clear
27-Dec-15							Gone but pool water clear
28-Dec-15							Gone but pool water clear
29-Dec-15							Gone but pool water clear
30-Dec-15							Gone but pool water clear
31-Dec-15							Gone but pool water clear
1-Jan-16							Gone but pool water clear
2-Jan-16							Gone but pool water clear
3-Jan-16							Gone but pool water clear
4-Jan-16							Gone but pool water clear
5-Jan-16							Gone but pool water clear
6-Jan-16							Gone but pool water clear
7-Jan-16							Gone but pool water clear
8-Jan-16	70	30	7.5	0	300	7.7	Pool water clear green algae on afternoon sun walls. About 3 Trichlor tabs consumed

 

[MarianParoo]

Hi, Chris. Welcome back. You know what we're going to say, right? Hint: starts with an S and ends with an M.

edit:

I didn't intend to sound so flippant... With visible algae, you must take your FC up to shock level (12ppm or above, never below), and keep it there, brushing daily. An OCLT will let you know when you are done.

 

[Jezza]

Until you SLAM you are merely holding the algae at bay with your FC.

The key part of the SLAM is to bring your FC up to shock level and then maintain it until you completely get rid of it.

 

[setsailsoon]

Hi, Chris. Welcome back. You know what we're going to say, right? Hint: starts with an S and ends with an M.

edit:

I didn't intend to sound so flippant... With visible algae, you must take your FC up to shock level (12ppm or above, never below), and keep it there, brushing daily. An OCLT will let you know when you are done.

Marion,

Yep that's exactly what I thought you'd say. So I've modified the plan to SLAM in the morning... and finish when I pass the SLAM stop checks.

Thanks.

Chris

 

[MarianParoo]

We'll be here if you need us!!!

Test and add as often as you can and it will go faster. Brush that visible algae vigorously and often. Check for other hidden areas too. Good luck!

Marian

 

[setsailsoon]

Marion,

Thanks! Anticipating a required slam I stocked up on acid and liquid chlorine plus reagent refills before we left on vacation. I cleaned the filter last night and got up early to brush vigorously and adjust the PH. About 4 hours later the PH was stable (tested at 3 locations 20 min apart). I over-shot a little to 7.1 but at low levels my pool PH increases rapidly so I'm sure I'll be in range tomorrow. So I began liquid chlorine additions to get to FC 16 and have about 28 oz left. I also left the remaining trichlor tablets (~2 remaining) since my CYA is still only 30.

The algae on the walls/fixtures was very easy to remove and slightly off-green... maybe dead or dying? I'm pretty sure it would also be on the floor except for my cleaner that was running 10 hr/d for the last 3 weeks and set so it wouldn't climb the walls. Here's a puzzling part for me. Clearly I have a lot of algae and clearly I'm killing a lot of it because the water is clear. But my CC level for every test since Nov of last year is 0. How could that be? My reagent is very new. Excellent filtering may be part of the answer but what about the dissolved water-soluble organics that are a product of cell destruction? These are not removed by filtration. The more I learn about this the more interesting it gets!

Chris

 

[MarianParoo]

While you're at the store getting more liquid chlorine/bleach, we will get some reading together for you about CC's!

 

[setsailsoon]

While you're at the store getting more liquid chlorine/bleach, we will get some reading together for you about CC's!

Thanks, I still have 4 gal left. Here's my readings so far:

8 am- Added 128 oz muratic, scrubbed pool 12 pm- PH reading 7.1 added 128 oz 10% CL bleach 1 pm- FC 18, PH 7.4 started solar heater pump pr 15 psi 3 pm- FC 21 PH 7.4, switched pump to 24 hr, remove tabs from chlorinator for OCLT

Pool looks great!

Chris

PS I know PH is unreliable at these FC levels but I'm checking PH with color test plus calibrated meter just to see what happens as I approach 10 ppm FC when the slam is over. Just curious.

 

[marcgr]

Just curious... how was algae able to grow when you had sufficient FC the whole time? Was it just the lack of brushing?

Marc

 

[setsailsoon]

Marc,

Great question. I'm hopeful the experts will chime in on this but my conclusion is exactly that. Here's why. I had the pool cleaner running 10 hours per day and my type of cleaner is very good at vacuuming algae. I had it set so it would not climb the walls. I had no visible algae on the pool bottom. Also the normal flow is a little less than half of the return to the spa which overflows to the pool. The spa seats, walls, and floor also had the thin almost translucent off-green algae coating. The pool cleaner doesn't operate in the spa.

So I'm also concluding the algae must be dead or dying since it's removed in the cartridge filter. I've read a lot about pool cartridge systems lately and they won't remove single celled live algae particles very well at all. The live cells do not clump since their strong positive charged cell walls makes them repel each other like two N poles of a magnet. It's only after they die or suffer cell wall damage that the charge breaks down and they start to stick together to form clumps of at least 3-4 cells that are easily trapped in my cartridge filter.

Thanks for the great question and please remember I'm really just a newbie here so my response is more inference than confirmed science that I'm sure the experts will add. I really do enjoy being on the steep part of the learning curve though!

Chris

 

[MarianParoo]

Sorry, I ended up sick today. Better now.

Brushing does break up the protective biofilm that algae uses to protect itself. By brushing, you "scratch" the biofilm surface which allows the chlorine to enter the cells and work its magic.

Frequent brushing (even with a cleaner which will miss certain areas), is one of the most important things you can do for your pool, and it is one of the most overlooked. My other favorite is cleaning out the light niches at least once a year if not twice.

 

[setsailsoon]

Sorry, I ended up sick today. Better now.

Brushing does break up the protective biofilm that algae uses to protect itself. By brushing, you "scratch" the biofilm surface which allows the chlorine to enter the cells and work its magic.

Frequent brushing (even with a cleaner which will miss certain areas), is one of the most important things you can do for your pool, and it is one of the most overlooked. My other favorite is cleaning out the light niches at least once a year if not twice.

Marion,

Thanks much for the reply and I hope you're feeling better. Brushing seemed to help the pool a LOT and I have to say it was very easy. I scrubbed but it didn't really help so much, the area looked clean even after a sweep motion without contact. But true to TFP SLAM process I scrubbed. The 3 pm and 11:30 pm readings are the same PH 7.4 FC 21... can't wait 'till the morning and thanks again for the reply even in recovery mode on your part!

After this SLAM is over I'd like to learn about algae spores and of course their Cl resistance. I've got a feeling they may play a part here.

Best regards,

Chris

 

[MarianParoo]

You may want to check too if the algae is in an area of low circulation. You can watch a ping-pong ball drift across your pool and see if it comes near that area. If not, you could adjust your returns a tad. However, that will never replace the need for brushing.

 

[setsailsoon]

Marion,

Here's my new results:

10:00 pm FC 21 PH 7.4 CC 0
07:00 am FC 20.5 PH 7.5 CC 0

Pool looks fantastic! No visible algae anywhere. So It looks like my SLAM is technically finished. I think I'll scrub again today and tomorrow just in case it's hidden but I'll let the chlorine drift down to normal now.

If anyone can explain why my CC has been zero throughout I'd appreciate if you could chime in. Right now I'm just baffled by this.

Marion, thanks again for your help.

Chris

 

[setsailsoon]

Just curious... how was algae able to grow when you had sufficient FC the whole time? Was it just the lack of brushing?

Marc

Marc,

To further respond on your question I think the algae must have been in an area of my pool that didn't get good mixing so there was a localized area of low FC even though the rest of the pool was good. Several experts offered that as an explanation and it makes a lot of sense. I guess the mechanism would begin with low FC in a localized area and algae spores germinate then are killed pretty soon and start to turn brownish and clump together. Then I scrub the walls and they fall to the bottom to be vacuumed into the filter where they are trapped and ultimately removed from the system. There are clearly off-green algae cells coming off my filter cartridge when I clean it. I'm probably avoiding a nasty bloom only because my FC level in the pool is adequate.

All guesses on my part but it does sort of make sense and most importantly the algae is so easily removed it isn't interfering with my use of the pool.

Chris

 

[MarianParoo]

Many people will do one extra day at slam levels just to make sure they are really done. Just saying.

 

[setsailsoon]

Marion,

Good point and not too hard since I'll have to wait a few days to get below SLAM level for my pool. I might as well just leave the pump on and scrub a little extra.

Thanks.

Chris

 

[MarianParoo]

Good choice. I am sorry, I can't find a definitive explanation about 0 CC and algae. I just know it can happen but I can't explain why in the depth you are looking for.

 

[setsailsoon]

Marion,

No problem on the 0 CC and thanks so much for all you've done. I did find a really in-depth post from Chem Geek that discussed the reactions with FC and CC that result in dissipating ultimately via conversion to N2 gas. I've also seen these reactions described elsewhere on the net. Of course non of this really changes anything it just helps me understand.

Best regards,

Chris

 

[MarianParoo]

I'm glad YOU could understand Chem Geek's explanation! I was looking for something us non-chemists could understand, tee-hee!