My pool is NOT trouble-free!

[SiliconFiend]

Hello all,

I'm struggling with persistent low-grade green algae, and either it's very resistant to chlorine or we have some well-hidden CYA (or something else) which is inhibiting the chlorine's oxidizing action at the levels recommended here. This is our fourth summer with our pool, and I've followed the advice of TFP (bleach as primary sanitizer, correlated with CYA levels) since we first started using it. The pool was a green swamp when we moved in, so on the first opening I drained, pressure-washed and refilled it. First year was great, no signs of algae for 3 months, then a big bloom which I eventually got under control (again following the advice of this site). Subsequent years I have blasted it with bleach on opening to kill off the algae but I seem to fight with algae growth continuously throughout the summer unless I SLAM it (and hold) to 2-3 times the recommended shock level.

Some pool facts:

• Pool is gunite/plaster (green tinted plaster, which makes it fun to see algae), about 17,000 gallons (just a guess, but its response to chemical additions correlates). Based on permit history, the pool is about 35 years old, and *may* have the original plaster (if that's possible). The plaster is in very bad condition--rough with lots of pop-offs, a number of rust spots, etc. Fortunately the pool still holds water quite well. We're planning to resurface after this season.
• Bleach: I use the 10% bleach from Home Depot. Seems to work okay, and it's readily available. 1 gallon raises the chlorine by 6 ppm.
• Cover: We use a floating solar cover. It's only 3 years old but is on its last season. The high chlorine levels from previous years significantly weakened it.
• Maintenance: I normally test the pool every 3 days, and add a half gallon of bleach. Doing it this way, the pool cycles between 6 and 9 ppm (higher than the 2 to 5 ppm recommended by the pool calculator) but I still get visible algae growth. I brush once a week. Tonight there were visible green clouds when I brushed. The pool is pretty clear and generally looks good, even when algae is starting to grow.
• Filter: DE filter, used exclusively with fiberclear (or equivalent) since first installed. All new grids at the start of the season. High chlorine levels destroyed the original grids in 3 years (broken embrittled plastic spines, holes in fabric).
• Pump: I run the (single speed) pump about 4 hours a day, which should be about 1 to 1.5 turnovers.
• Trees: The pool has a lot of oak trees (live oak, valley oak, black oak, etc.) around it, but I've trimmed them back so they're not directly over the pool. They don't drop a huge amount of stuff in the pool, and what they do drop tends to get picked up by "Squirt" (booster pump driven pool cleaner).
• Winter: I'm in California so I don't winterize per se, just raise the chlorine to about 10-15 ppm and then put the safety net and leaf cover over it. Try to run the pump a few hours a week, and add algaecide if the algae appears to be getting out of hand. Normally open the filter and clean the grids at opening.
• Borates: I added borates in the middle of last season (20 mule team + acid). It seems to work for its primary purpose of buffering rises in pH (but the buffering is asymmetric because it the pH seems to fall quickly), but it hasn't change anything with regards to the algae. If anything it seems to be worse this year.
• Combined chlorine: Always tests at 0, or at most 1 drop (so less than 0.5)
• CYA: For whatever reason, this always returns to 0 or close to it when the pool is first opened. It does not appear to be converting to ammonia, however, because the CC is always 0. I normally use some pucks of trichlor in a floater at the beginning of the season to bring up the CYA to about 30. I'd guess the level was about 10 at the beginning of this season, and I have added maybe about 3 pounds of trichlor so it should be around 20.
• Polyquat 60: I use this over the winter to keep the algae away. It works great, but it seems to load up my filter and make for short filter times between backwash until I remove and clean the grids. I considered using it tonight but it seems to interact strongly with the bleach--they destroy each other. Also, I don't want to break down the filter again right now.
• Phos-free: I've actually considered going to [BIG NATIONAL POOL STORE] and trying Phos-free just to try to lower the phosphate levels (I don't think they're particularly high) and help keep the algae under control. Please save me from this.

Tonight's test results (Taylor 2006): FC 7.0, CC 0, temp 82 °F, pH 7.3. Not tested tonight, but previously (and they're quite steady): CYA ~20, TA 110, CH 325, Borates 50
I dumped in 4 gallons of bleach tonight so theoretically the levels should be 31 ppm. I guess I'll buy more tomorrow and keep adding it to keep the levels up until it seems to be gone.

Questions:

• Why don't the recommended chlorine levels from the pool calculator keep the algae away, even after SLAMing it to 3x the shock levels? I don't want to keep destroying my equipment with high levels.
• Could the rough plaster surface be causing much of this problem? (I can see algae hiding in the edges of the pop-offs). If so, we're considering a pebble surface for the resurfacing. Wouldn't that rough surface have the same problem?

 

[Isaac-1]

Have you checked for hidden algae pockets under steps or perhaps in a light niche?

 

[anonapersona]

I suspect the light niche also. And the cover may be part of it as well.

 

[gwegan]

I would check the light and the plaster. If you have pop offs there may be locations where the algae has worked its way up behind the plaster and has insulated itself from much of the chlorine. It sounds like the algae doesn't come back immediately, is that correct?

 

[afrikaanmomma]

I suspect the light niche. I have a problem with ours almost every year. We unscrew the light and lay it out to float when we are SLAMing. Scrub the niche out. under the ladder steps is a great algae hiding place, too.

 

[ping]

I would also suspect that there is algae hiding in the pool somewhere that you have not seen. The rough plaster is not doing you any favors either and if your pool has dead spots you might need to brush 2-3 times a week.

Have you followed the SLAM process from start to finish by passing all three criteria in the past?

You should not need to raise the chlorine too much above the suggest SLAM level for the CYA level to clear the algae up. We suggest those levels so the equipment will not be damaged.

 

[brian4110]

fight with algae growth continuously throughout the summer unless I SLAM it (and hold) to 2-3 times the recommended shock level.

This makes my CYA level detector start to ping. How certain are you that your CYA test is accurate? I feel your pain and hope you can find a solution soon!

 

[JesseWV]

It certainly sounds like a pool with a higher CYA level.

 

[chem geek]

If the green algae is only showing up in areas with poor water circulation, then you could try changing the circulation pattern pointing the returns differently.

 

[SiliconFiend]

Sorry, I didn't see any replies to this thread until tonight, even though I checked earlier today. Weird. The light niche is a good idea; I know it had a lot when I first cleaned & pressure-washed. I'll try to get the light out and brush the niche. There is no ladder, only steps and a couple benches, so no hiding place for algae there. I suspect the pop-offs are a big part of the problem (I hope so, anyway, because that means it won't be such a fight once we resurface). I know I can see algae hiding in the corners of the pop-offs--I scrub it as best as I can, but I'm sure there are crevices at the margins.

The algae tends to collect in a broad area around the middle of the pool. I have only 3 pool returns (plus 1 in the spa) so I'm limited in controlling the circulation. Also I think the eyeballs need to be replaced anyway--they're probably original, and they don't move easily (I didn't try too hard for fear of breaking something).

I haven't had the water tested yet this season by [BIG NATIONAL POOL STORE] but I have in the past and they correlate pretty closely with my testing so I'm reasonably confident in the CYA. I might take a sample down there if I get a chance and see what they think. Regarding the levels, that is, not any advice ($$$) they might give.

I guess I'll let the chlorine drift down so my family doesn't kill me for making the pool unusable when the weather is nice. I'll probably try to maintain it at around 15 for a while though.

The thing that bugs me is even if there is some (mostly hidden) algae in the pool, why is it growing steadily even when I maintain my normal chlorine level not far from the recommended shock level of 11 ppm? And why wouldn't it show up as CC?

 

[jagster]

I have similar problems. I opened up my pool out in the country this year with green swamp. Did all the slamming stuff and it turned blue but has been cloudy. Has taken 2-4 weeks to get pretty clear though not perfectly clear. Added some big pool store floculent to clean up the dead algae it definitely helps but not perfectly clear. Just have a sand filter.

The pool also has oak trees and other trees around it trimmed back. I can shock hard, but no matter what I seem to do algae grows in the steps area and in the shallow end and other random places with poor circulation perhaps. Bleach alone does not seem to do the trick like everyone raves on here.

I have added Borates this past weekend to see if it helps but am not convinced it will. The agae comes literally in hours at normal chlorine levels recommended based on CYA levels. I had measured 100+ cya but now measure 30 or so. I don't know? lol I can shock it up high and let it drift back down when I travel for work weekly, it seems to work pretty well but the aglae is always there. Sometimes green sometimes brownish looking algae. I also tried one gallon of "professional" anti phosphates (man that's expensive) and it did nothing at all. Is Algaecide or anti phosphate work better for you Siliconfiend? I sometimes don't trust my CYA measurements; I take it at a level below surface about arms length down in deep end. Pumps runs a lot while I play then when I travel it's for 6 hours, 38000 gal pool.

I can understand your frustration with aglae and chlorine levels, for sure! You keep your levels much higher. I think when I shock it really high it stays away but immediately reappears upon falling to "normal" levels based on CYA. Crazy!

Thanks

 

[BoDarville]

In addition to the light niches, check around and under any ladders or removable steps if either of these apply to your pool.

If you have pop offs there may be locations where the algae has worked its way up behind the plaster and has insulated itself from much of the chlorine.

While not common, this is certainly is a possibility. A pic might help us diagnose the likelihood of this.

• Polyquat 60: I use this over the winter to keep the algae away. It works great, but it seems to load up my filter and make for short filter times between backwash until I remove and clean the grids. I considered using it tonight but it seems to interact strongly with the bleach--they destroy each other. Also, I don't want to break down the filter again right now.
• Phos-free: I've actually considered going to [BIG NATIONAL POOL STORE] and trying Phos-free just to try to lower the phosphate levels (I don't think they're particularly high) and help keep the algae under control. Please save me from this.

Do not bother with algaecides - they will do nothing for an existing algae bloom. Also, do not bother with phosphate removers. One of our Moderators has phosphate levels ranging from 2,000 - 4,000 ppm and has no problems with algae. Proper chlorination according to the pool's CYA level will keep algae at bay regardless of the phosphate level.

A reliable CYA reading is critical for ongoing management of the pool along with properly following the SLAM process. Suggest checking the links in my signature as all of them apply to managing and SLAMming a pool properly. You need to follow the SLAM process exactly as outlined - a single or intermittent "shock" dose of chlorine will not get it done. The SLAM process is effective when it is done properly; It is, however, not necessarily convenient on the part of the pool owner.

 

[jagster]

After reading several posts for hours, I'm fairly confident I have mustard algae. I will try slamming and then raising to mustard shock levels, and cleaning more thoroughly and see if I can shake it. I think this is best approach.

 

[SiliconFiend]

In addition to the light niches, check around and under any ladders or removable steps if either of these apply to your pool.

While not common, this is certainly is a possibility. A pic might help us diagnose the likelihood of this.

Here's a couple:

And just for fun, here's a "before" picture when I first drained it:

Don't you love the green plaster color? Very 70's. Goes great with the brown fleur-de-lis water line tiles. Sorry, the pics are somewhat hard to see. The sun just set and the pool light doesn't illuminate them very well (although it highlights them quite clearly when it's dark). The pop-off shown by itself (same as the right-most one in the wider pic) is probably about 4-5 inches across. The pic was taken at the shallow end, probably 3.5 feet deep. There are larger ones, too (up to about 10-12 inches), and a bunch of smaller ones. The algae does tend to collect in them, but you can't see it now because I brushed them really well yesterday with my small stainless algae brush.

Do not bother with algaecides - they will do nothing for an existing algae bloom. Also, do not bother with phosphate removers. One of our Moderators has phosphate levels ranging from 2,000 - 4,000 ppm and has no problems with algae. Proper chlorination according to the pool's CYA level will keep algae at bay regardless of the phosphate level.

I dunno, the poly 60 works quite well in the winter. In February it halted an advanced bloom in its tracks. I suppose it's not lasting, though (but neither is bleach!). To jagster: I've never tried phosphate removers. They're expensive (but so is the poly 60).

A reliable CYA reading is critical for ongoing management of the pool along with properly following the SLAM process.

Well, I'll check it again but it can't be very high since it started the season at around 10 and I've only added one floater's worth of pucks this season (maybe 3 pounds?).

Suggest checking the links in my signature as all of them apply to managing and SLAMming a pool properly. You need to follow the SLAM process exactly as outlined - a single or intermittent "shock" dose of chlorine will not get it done. The SLAM process is effective when it is done properly; It is, however, not necessarily convenient on the part of the pool owner.

Thanks. I've read those posts in the past, but I'm sure I'm not following the procedure exactly. The thing is, the chlorine consumption is so predictable (1 ppm/day) whether there is an active algae bloom or not, so the OCLT doesn't seem to tell me much. Also, brushing the pool is the worst part of pool ownership for me. It's not even the physical effort, it's the time--takes about an hour to do it properly...! The other issue with following the SLAM procedure exactly is that with electricity at around $0.35-0.45/kWh (tier 4) it kills me to run my single-speed pump continuously for days on end. Even at only 4 hours a day it still costs me about $100/month over my baseline electrical bill to run the pump (an upgraded control system and 2-speed pump motor are also in the offing, hopefully after this season). At some point the algaecide and/or phosphate removers are cheaper (and easier).

 

[Zadd]

From what I understand the mustard algae will disappear during a normal SlAM but will reappear several weeks later. So if you can SLAM to completion simply add an extra day at Mustard agae level for 24 hours then let Chlorine levels drop back to normal.

 

[chem geek]

I have similar problems. I opened up my pool out in the country this year with green swamp. Did all the slamming stuff and it turned blue but has been cloudy. Has taken 2-4 weeks to get pretty clear though not perfectly clear. Added some big pool store floculent to clean up the dead algae it definitely helps but not perfectly clear. Just have a sand filter.

The pool also has oak trees and other trees around it trimmed back. I can shock hard, but no matter what I seem to do algae grows in the steps area and in the shallow end and other random places with poor circulation perhaps. Bleach alone does not seem to do the trick like everyone raves on here.

I have added Borates this past weekend to see if it helps but am not convinced it will. The agae comes literally in hours at normal chlorine levels recommended based on CYA levels. I had measured 100+ cya but now measure 30 or so. I don't know? lol I can shock it up high and let it drift back down when I travel for work weekly, it seems to work pretty well but the aglae is always there. Sometimes green sometimes brownish looking algae. I also tried one gallon of "professional" anti phosphates (man that's expensive) and it did nothing at all. Is Algaecide or anti phosphate work better for you Siliconfiend? I sometimes don't trust my CYA measurements; I take it at a level below surface about arms length down in deep end. Pumps runs a lot while I play then when I travel it's for 6 hours, 38000 gal pool.

I can understand your frustration with aglae and chlorine levels, for sure! You keep your levels much higher. I think when I shock it really high it stays away but immediately reappears upon falling to "normal" levels based on CYA. Crazy!

Thanks

After reading several posts for hours, I'm fairly confident I have mustard algae. I will try slamming and then raising to mustard shock levels, and cleaning more thoroughly and see if I can shake it. I think this is best approach.

If you have tried all those things and still have this green/brown stuff, then why do you think it's algae and not pollen, dirt or other debris (organic material) from trees? Also, did you try adding DE to your sand filter for improved filtration (rather than using a flocculant)? High chlorine levels also bleach out organic matter but more slowly so if you have such being blown into the pool then at more normal chlorine levels it may show up more. If you can capture some of the material and feel it, that can help. If you can look at it under a microscope, then that can be definitive.

If you have yellow/mustard algae as you surmise, then this takes roughly double the FC/CYA level to stop its growth. However, it tends to prefer shade and it poofs up like dust. You have to completely get rid of it from the pool or else it will come back at normal FC/CYA levels.

 

[SiliconFiend]

Good news! I can't get the light out of the niche. :-| My screwdriver just spins in the screw head like it's stripped. I last had it out 3 years ago when I first cleaned out the pool, but I don't remember any particular difficulty with it. I can't see the screw head very well, though, so I'll have to get in the pool with goggles to take a closer look at it, probably this weekend. In the meantime, I'm returning the pump to its regular schedule and letting the chlorine drift back down to the 6-9 range. At the least I've bought myself a few weeks of reprieve from the worst of the algae growth anyway.

 

[SiliconFiend]

Well, it turned out that the light was held in by a hex head cap screw, so I was able to get the light out with no problem. I brushed out the niche and got some green puffs, but there is some plaster in there and it's likely been breaking down somewhat over the last 3 years, so the green puffs could be plaster and not algae. The rest of the pool looks algae-free, but it's hard to know for sure, especially in the corners of the pop-offs. I'll keep the chlorine level up a little for this week but with a normal pump schedule, just to (hopefully) take care of any remaining algae.

 

[JesseWV]

I would leave that light cover off for a week or so to let it be fully exposed to shock level water. I'd probably also be crazy enough to fill a pump sprayer with 50/50 bleach/water solution and spray in there real good.

 

[SiliconFiend]

Thanks for the tip. I left the light out for over a day (while the level was around 15 ppm) and brushed it well a couple times. If there was algae, it was hard to tell with the (green) plaster dust flying around. I think I'm going to call it good for now, keep my chlorine up at the 6-9 range and see how it goes the rest of this summer.