Recovering from Algae

[dfeist]

Hi,

I'm maintaining a pool that my family use at a rented property. I know I have a number of important equipment limitations but given we are renting it doesn't make sense for me to invest in any permanent improvements. Let me explain what I have, then I'll continue with my question:

- Pool size: Aprox 48,000 liters
- Material: Plaster (i assume, it's painted)
- Pool has no permanent circulation/filtering equipment

I have purchased
- 3/4 HP pump (i connect this up when i use it)
- Vacuum head and necessary pipes (when i vacuum pool this water is thrown away and then a refill as required)
- Simple OTO/PH drop based test kit
- Some 3-way HTH test strips that include total alkalinity (I live in Argentina and have found it impossible to get any decent test kit yet, i bought these strips just to get an idea of total alkalinity.)

Fill water:
- PH 8+
- Total alkalinity appears to be around 300 given it turns test strip blue not green.
- Pool was filled with this water about 4 mths ago

Chlorine:
- I'm now using bleach (10%) exclusively
- In the past 4mths i've used di-cloro granulated a lot (probably 8kg in total) and 1kg of pucks. I know this is a a lot but given that i must throw out some 3000l each time I vacuum I'm assuming CYA can't be too high.

Me problem/question is the following:

I've been maintaining this pool ok for about 3mths and everything was fine but then water gradually got clouder and clouder even though i was still using the same amount of chlorine. In hindsight this was probably caused by the fact that the PH was creeping up with oxygenation and new fill water being added and the chlorine was less and less effective. Also during this time the water temperature went up from around 21C to around 28C (summer started, i'm in southern hemisphere).

I applied a shock treatment of chlorine (10l of 10% bleach ) but cloudiness remained. Unsure if it was an algae problem or just dirt in suspension i used a clarifier. This made the water look clearer but also meant i saw small coin-size green patches on the surface and larger irregular patches of green on the bottom of the pool. I vacuumed the apparently loose sand-like stuff up from the bottom of the pool but the next day it was back again. I realized this might be a PH issue and when I measured it it was around 8 so I shocked again after lowering PH to 7.6/7.8. A lot less sand-like greenish stuff reappeared on the bottom of the pool (a bit does though, not sure it if dirt, precipitated remains of algae of live algee), the chlorine when measured in the morning was still above 5ppm and the shallow-end looks looked very clean/clear. The problem is that at the deep end of the pool (2m) although i can now clearly see the bottom now and the water when using the pool looks clear, when I look at the pool from a short distance the water at this end of the pool still looks somewhat cloudy and a bit blue-green (a lot more so when look at it from an angle rather than straight down).

Yesterday i lowered ph even further to 7.3 (6kg of dry acid hoping that i'd also reduce TA a bit and improve the PH creep issue) and shocked again (7l of 10% bleach assuming CYA of 50) but didn't notice any improvement this morning.

Am i over the algae bout? I'm not quite there yet and need to keep shocking? Or you can't help much because i have such poor pool/test equipment (hopefully you can still give me some pointers)?

thanks!
Dan

 

[woodyp]

I don't know how on earth you will ever maintain that pool without some form of filtration system connected to the pump. Is the pump you have a portable type?

 

[dfeist]

I don't know how on earth you will ever maintain that pool without some form of filtration system connected to the pump.

I seemed to manage for a while, although it wasn't being used so much then. I have a clear understanding of what went wrong (PH) so although not ideal, surely I must be able to at least keep it in decent-shape and keep algae at bay. As I said i'm not really in a situation where i want to invest much in someone else's pool.

Is the pump you have a portable type?

It's like this: http://www.vulcano-sa.com/productos/eb01.jpg . It can be fitted somewhere, or put on a trolley or just carried around, it's not specifically portable, no.

Aside from my lack of equipment i think there are some more general questions here about recovering from algae that it would be interesting to hear some ideas/comments on..

Dan

 

[JohnT]

I don't have much hope for you to recover. The dead algae will have to go somewhere.

I doubt your pH had anything to do with it.

Here a couple of good articles that discuss the topic

Defeating Algae

Turning Your Green Swamp Back into a Sparkling Oasis

 

[dfeist]

I don't have much hope for you to recover. The dead algae will have to go somewhere.

I doubt your pH had anything to do with it.

Here a couple of good articles that discuss the topic

Defeating Algae

Turning Your Green Swamp Back into a Sparkling Oasis

Yeah, i've read those articles in detail. Agree the pH isn't the issue now, but probably was the cause of the initial outbreak due to reduced chlorine effectiveness at 8.2.

So your assumption is i'm over the main outbreak, but the water needs a good filtering now and not having a filter is an issue? How effective is clarifier+vaccum if a filter is not available, or should i really consider getting a filter?

thanks!
Dan

 

[chem geek]

Dan,

Agree the pH isn't the issue now, but probably was the cause of the initial outbreak due to reduced chlorine effectiveness at 8.2.

This is not true. There is no mystery here. 8 kilograms of Dichlor in 48,000 liters increases Cyanuric Acid (CYA) by 84 ppm (and FC by 92 ppm) while 1 kg of Trichlor pucks increases CYA by 11.6 ppm (and FC by 19 ppm) so you've increased CYA by over 95 ppm from where you started. Even if you vacuumed once a week for 3000 liter removal of water, that is only a dilution of 6.25% per week. The 95 ppm increase is over 4 months (about 17 weeks) so is around 5.6 ppm per week. With the dilution, the increase is (48,000-3000)/48,000 * 5.6 = 5.2 ppm so after 4 months even with the dilution this is around an 88 ppm CYA increase. Also, the cumulative 104 ppm FC accounting for dilution is only 0.87 ppm FC per day which seems awfully low unless the pool is not exposed to very much sunlight or you were keeping the FC level way too low. Perhaps the FC level was only at around 2 ppm or even less.

As the CYA got higher, you needed to raise the FC level to prevent algae growth. You are lucky you lasted as long as you did before the water turned cloudy. The FC should be around 7.5% of the CYA level in a manually dosed pool to prevent algae growth. I'm guessing that after 3 months your FC was only around 3% of your CYA level (2 ppm FC with 66 ppm CYA) when the algae was able to grow faster than the chlorine could kill it so the water started to turn cloudy. The higher pH didn't help, but was not the cause of the problem. Please try to remember the following chemical facts that are independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

Generally speaking, one should never use Dichlor as a regular source of chlorine. It's fine when you know you need to increase your CYA level, but otherwise it should not be used. Trichlor pucks similarly should be managed carefully. Even with a low 1 ppm FC per day chlorine usage, after 6 months with Trichlor the CYA increases by over 100 ppm.

As for your shock treatment with chlorine, 10 liters of 10% bleach in 48,000 liters would raise the FC by 21 ppm, but that isn't enough to clear a pool of algae when the CYA is so high. We don't know what CYA level you started with, but we know it's at least 88 ppm higher and that would require a SUSTAINED FC level of 35 ppm to clear the algae quickly -- shocking is not a one-time dosing process. I suspect your CYA level is even higher and the practical thing to do is a partial drain/refill to lower the CYA level since that will let you shock with less chlorine to kill off the algae and you'll need to get your CYA level lower anyway.

At this point, if you do not dilute the water to lower the CYA level, you would need to maintain a higher FC level to keep the algae from coming back -- probably at least 4 ppm though the recommended minimum at 88 ppm CYA would be 7 ppm FC for a manually dosed pool. However, you will probably have higher chlorine loss at around 1.5-2 ppm FC per day or maybe higher if you've still got algae that isn't visible. Without a good test kit, it will be hard to know when you are truly done shocking the pool and killed off all the algae. The procedure requires an accurate FAS-DPD chlorine test so that you can measure your overnight chlorine loss and the Combined Chlorine (CC) level as well.

If I were you, I'd work on diluting your water, then shocking again at the lower CYA level, then maintaining your pool using bleach or chlorinating liquid. Eventually, you'll need more CYA and can use a puck on occasion, but not very often. Even though you may not be able to get a Taylor K-2006 test kit, see if anyone has a Palintest SP 315C and maybe an SP 300 FAS-DPD as well.

Also, as John points out, without good circulation, it will be hard to clear and maintain your pool.

Richard

 

[dfeist]

With the dilution, the increase is (48,000-3000)/48,000 * 5.6 = 5.2 ppm so after 4 months even with the dilution this is around an 88 ppm CYA increase.

Ok so although pH maybe something i need to keep an eye on given I have such high alkalinity in this case it was most certainly a CYA issue. I'd only guestimated and hadn't done the cumulative calculations as you have.

Also, the cumulative 104 ppm FC accounting for dilution is only 0.87 ppm FC per day which seems awfully low unless the pool is not exposed to very much sunlight or you were keeping the FC level way too low. Perhaps the FC level was only at around 2 ppm or even less.

I was using bleach also, switching between the two so it wasn't that low, but still probably not enough given the CYA.

As the CYA got higher, you needed to raise the FC level to prevent algae growth. You are lucky you lasted as long as you did before the water turned cloudy.

It turned cloudy once before when I was away for a a few days but 10l bleach fixed it overnight and water was perfect again. (i'd only used 1kg pucks and bleach up until then though)

Generally speaking, one should never use Dichlor as a regular source of chlorine. It's fine when you know you need to increase your CYA level, but otherwise it should not be used. Trichlor pucks similarly should be managed carefully. Even with a low 1 ppm FC per day chlorine usage, after 6 months with Trichlor the CYA increases by over 100 ppm.

I know that now, before it just seemed most practical alternative :-(

As for your shock treatment with chlorine, 10 liters of 10% bleach in 48,000 liters would raise the FC by 21 ppm, but that isn't enough to clear a pool of algae when the CYA is so high. We don't know what CYA level you started with, but we know it's at least 88 ppm higher and that would require a SUSTAINED FC level of 35 ppm to clear the algae quickly -- shocking is not a one-time dosing process. I suspect your CYA level is even higher and the practical thing to do is a partial drain/refill to lower the CYA level since that will let you shock with less chlorine to kill off the algae and you'll need to get your CYA level lower anyway.

Pool was freshly painted/filled and therefore had 0 CYA when i took it over, but still 88 is high as you say.

If I were you, I'd work on diluting your water, then shocking again at the lower CYA level, then maintaining your pool using bleach or chlorinating liquid. Eventually, you'll need more CYA and can use a puck on occasion, but not very often. Even though you may not be able to get a Taylor K-2006 test kit, see if anyone has a Palintest SP 315C and maybe an SP 300 FAS-DPD as well.

OK, i'll do that. I very much doubt i can get any of those kits here, but i'll work on getting a kit from the US. If i were to get just the FAS-DPD test can i rely on strips for alkalinity (is this that important even?) and CYA e.g. aquachek silver 7-way? I'm just thinking about bulk reduction for having one sent, the CYA kit and kits that include it are particularly bulky compared to others.

Also, as John points out, without good circulation, it will be hard to clear and maintain your pool.

I try to run the pump as much as possible, but there is still no filtering so only what precipitates gets removed. i might consider getting a filter along with a trolley to put pump/filter on, then i can filter water and also when i vacuum I assume i won't have to throw the water out and refill with the high-ph high-alkalinity groundwater in this area. Correct?

many thanks for the detailed reply,
Dan

 

[chem geek]

OK, i'll do that. I very much doubt i can get any of those kits here, but i'll work on getting a kit from the US. If i were to get just the FAS-DPD test can i rely on strips for alkalinity (is this that important even?) and CYA e.g. aquachek silver 7-way? I'm just thinking about bulk reduction for having one sent, the CYA kit and kits that include it are particularly bulky compared to others.
:
I try to run the pump as much as possible, but there is still no filtering so only what precipitates gets removed. i might consider getting a filter along with a trolley to put pump/filter on, then i can filter water and also when i vacuum I assume i won't have to throw the water out and refill with the high-ph high-alkalinity groundwater in this area. Correct?

Do yourself a favor and get a proper complete kit from the U.S. See if Dave can ship you a TF-100 or a TF-100 XL. If not, then see if you can get a Taylor K-2006 or a K-2006C. The "XL" and "C" versions have more reagents so will be more economical for you to not have to reorder as often, but you'll need to keep the reagents in a dark cool place to have them last longer. I would NOT use the test strips. You want accuracy -- see this post to see why test strips are not as good as drop-based tests.

The fact that you are able to clear the pool as much as you have in spite of no filtration is a testament to the power of chlorine oxidation. Nevertheless, chlorine doesn't oxidize everything and in particular if people use suntan lotion you will find that chlorine won't be able to get rid of it completely. It either has to be filtered out or you might be able to purchase enzymes that can help break them down (but that's extra cost). You are correct that if you get a filter, then you can vacuum to the filter rather than to waste, though ultimately you will need to clean or backwash your filter at some point which will use up some water, though not as much as your regular vacuuming.

 

[dfeist]

Thanks for all the advice. I'm doing the following, i'll let you know how i get on:

- Emptied 5/9 of pool water this afternoon (not filled it yet)
- Will add 6l 10% bleach tonight (water still appears to have around 7pm from last nights miscalculated shock) which should bring it up to 35ppm. (Seems its the same amount of bleach required as if i fill and reduce CYA first, so doing this to not loose a day)
- I have nothing to test chlorine levels above 5pmm or CC with any accuracy yet, so I guess once i fill the pool tomorrow I'll try do a 15ppm shock (CYA should now be down from 90 to 40 approx) just in case and then see what happens from there in terms of what the water looks like, adding around 2l 10% bleach every night.

- Going to get hold of a filter, even if i just put it on a trolley with pump.
- Currently working out which liquid tests are most important to have shipped to argentina and if i can get a tablet-based CYA kit shipped instead of 8oz bottles of reagent or not.

Dan

 

[dfeist]

I still havn't got the filter or test kit yes, working on those...

I thought I'd overcome the problem i first posted about but it seems i havn´t quite:

Thursday 6th:
- Emptied 5/9´s of pool and added 6l of 10% bleach (to bring up to 35pm)

Friday 7th:
- Deep end of the pool still looked greenish in the morning so i dumped in the other 4l from the 10l bottle, before there was too much sun.
- A few hours later the water looked a lot clearer.
- I filled the pool
- Water was looking great
- Didn't add any bleach in the evening because from what I could test (FC strip + 50% dilututed OTO test) ppm was still around 8ppm
- I added some clarifier planning to vaccum the next day and leave the pool perfect

Saturday 8th:
- Vaccumed pool
- Water clarity was much better than I'd seen in at least 3wks.
- By the evening chlorine was down to 2/3ppm (its middle of summer down here in argentina)
- Added 1.5l of 10% bleach to bring it up to 5pmm (maybe i should have aimed at 7 instead?)

I woke up this morning and although water still looks just as clear as it did yesterday the patches on the bottom of the pool have reappeared :-(

They are irregular patches of seemingly loose particles gathered together. They disperse and become much harder or impossible to see when disturbed and are very easily vaccumed up. They seems to be more of a khaki colour than green and are definitely not stuck to the floor. At the same time its definitely not sand.

I know i need to do an overnight FC test (but i won´t have the kit for a week or two) and i know i need a filter.

In the meantime I'm trying to resolve the problem with what i have. I´m wondering if if should have shocked for longer, of if its a different type of algae and i need to shock at a higher level, or if it´s something compeltly different and not algae at all (not sure what it could be though)

I can upload a picture if required.

Dan

 

[dfeist]

I can upload a picture if required.

Here are the pics...

it's looking less sand-like now, how do i know if its an algae (and what type) or pollen or something else thats precipitated due to clarifier?

[attachment=0:z0igesfj]P1020413.JPG[/attachment:z0igesfj]

[attachment=1:z0igesfj]P1020415.JPG[/attachment:z0igesfj]

thanks!

Dan

 

[frustratedpoolmom]

IF possible, you can examine the particles with a microscope to determine what it might be.

Without the proper test kit, you can't do the Overnight FC Loss Test, which is the best way to rule out organics.

 

[chem geek]

You can also take some of this green stuff out and feel it. The following is a rough guide for feel and viewing in a microscope.

SUBSTANCE ...... FEEL ............ MICROSCOPE
Algae ............... Slimy ......... Translucent, usually oblong, sometimes in filaments
Pollen .............. Squishy ...... Solid, round, sometimes with spikes
Dirt/Rock ......... Hard* ........ Solid, jagged

*or breaks apart into a brownish cloud

 

[dfeist]

I vacuumed it up and it came back the next night (less of it though).

Last night I added enough bleach to take ppm over 15 and checked to see what things looked like this morning. No change in appearance, water is still very clear and this stuff on the bottom had moved about but was still there in same quantify.

I can't really get hold of the stuff to see what it feels like as it's not stuck to the floor and disperses as soon as you go near it, it's not dirt though.

I don't have a microscope so I'm going to work on the hypothesis that it's precipitated dead algae and keep vacuuming and see what happens over a few days.

I should have FAS-DPD kit in 2wks to do overnight test if i still don't have it resolved by then.

thanks for all the advice!

Dan

 

[dmanb2b]

Dan, when vacuming, perhaps someone can hold an old set of pantyhose or a skimmer sock over the return? I'm thinking besides previously having an algae issue, your filter is not capturing the "dead" stuff.

 

[dfeist]

I don't have a filter (yet), so it's definitely not making its way back into the pool. This probably also explains why it hasn't already been cleared (assuming it is dead algae).

Dan

 

[Shane1]

It seems like you've done the impossible so far, keeping the pool clear with out a proper test kit and any filtration at all. In that first pic there looks like a drain cover at the bottom of the pool. Is it plugged? If it is an old drain, not plugged and not getting any circulation it could be a source for problems along with any other pluming that has uncirculated water in it.
Is there an old equipment pad or any sort of plumbing associated with the pool? Are you connecting the 3/4hp pump to any sort of existing plumbing?