Yes that is exactly what I think happened; Chlorine was probably on the lower end, storm happened at night and dumped a fair bit of water, pump was not on at night, didn't have time to add some extra chlorine in the morning, afternoon became slightly cloudy probably due to the top layer of rain water not mixing in well. Couple that with the water temp in the pool sitting at 30C and it was a recipe for disaster. I will be more prepared next time - if I know a storm is coming, add some extra chlorine the evening before and let pump run for a few hours at night.
Dealing with dead algae dust
- Thread starter Krulligo
- Start date
So another week has passed now and pool is still 99.5% clear (it's super clear and probably acceptable to most people) but not as sparkling clear as I remember it being before the algae started. It's definitely not getting any worse over the past week but hasn't been getting better. I kept checking OCLT every 2 or 3 days and I have no loss over night (and also no extra chlorine loss over during a sunny day compared to what I was used to). At night when I shine a bright flashlight in the water I can see extremely fine particles in the water.
Yesterday I turned the pool pump off early and let the pool water settle for about 15 hours. I looked at the pool this morning and finally and looked crystal clear like I was used to before. However, upon brushing the floor, as suspected there was dust all along the button of the pool that puffed up (you definitely did not notice it laying at the bottom of the pool, but a slight dusty cloud did form when you brushed around). I have a round pool so usually larger debris eventually accumulates in the center of the pool when the pump is turned off, but I did not notice that this happens with this dust, so it must be extremely fine. So after fully brushing, once again the water is back to looking very clear but dull.
So I'm pretty much sure this fine dust is getting through my sand filter and I need another means of getting it out.
Any suggestions? Things I am thinking about is either putting a white sock or thin weave fabric on the skimmer basket to try to catch the dust, adding DE to sand filter (although I have so far been reluctant to do this since I don't want to be dealing with potential DE dust in the pool in addition), letting the water settle for 24hours and vacuum floor to waste, or finally, giving up and using a clarifier product that might clump this stuff together and be captured by the filter.
SLAM process was great in quickly killing off the algae, but dealing with the last bit of extremely fine algae dust to go from super clear to sparkling clear water seems to be a nightmare.
Brief summary timeline of SLAM process:
July 12th - Storm at night - lots of water accumulated in pool.
July 13th PM - came home from work noticed the water has become slightly cloudy and green tinted (still could easily see the bottom). Measured chemicals - chlorine was 4.5ppm at this time, CYA was 30 which is what I have maintained it at, dropped pH a bit down to 7.2, upped my chlorine to 12-14 ppm. Water quite quickly turned from a green tint to a blue-whitish tint.
July 15th - I ended up turning pump off for the night, letting dead algae settle to bottom, and vacuumed floor to waste, this helped out a lot.
July 18th - maintained SLAM levels diligently until here, where water finally became crystal clear to my Wife's eyes, however to my eyes, was super clear but not really as crystal clear as it was before (maybe like 99.5% of the way there). Small fine particles seen with flashlight at night. I have passed OCLT every night since the 14th. We have been diligently brushing every couple hours to keep any dust in suspension to get it to pass through the filter.
July 26th (today) - I have been running chlorine at 8-10ppm every since - slightly above the max for my CYA, but below SLAM levels. Pool is neither getting any worse or any better, water still very clear but does not have that sparkle it did before. Between July 18th and 26th, I did a few OCLT and each time was no loss in chlorine. Pump was off for 15hours since yesterday evening, and some brown dust can be brushed up from the bottom of the pool.
Yesterday I turned the pool pump off early and let the pool water settle for about 15 hours. I looked at the pool this morning and finally and looked crystal clear like I was used to before. However, upon brushing the floor, as suspected there was dust all along the button of the pool that puffed up (you definitely did not notice it laying at the bottom of the pool, but a slight dusty cloud did form when you brushed around). I have a round pool so usually larger debris eventually accumulates in the center of the pool when the pump is turned off, but I did not notice that this happens with this dust, so it must be extremely fine. So after fully brushing, once again the water is back to looking very clear but dull.
So I'm pretty much sure this fine dust is getting through my sand filter and I need another means of getting it out.
Any suggestions? Things I am thinking about is either putting a white sock or thin weave fabric on the skimmer basket to try to catch the dust, adding DE to sand filter (although I have so far been reluctant to do this since I don't want to be dealing with potential DE dust in the pool in addition), letting the water settle for 24hours and vacuum floor to waste, or finally, giving up and using a clarifier product that might clump this stuff together and be captured by the filter.
SLAM process was great in quickly killing off the algae, but dealing with the last bit of extremely fine algae dust to go from super clear to sparkling clear water seems to be a nightmare.
Brief summary timeline of SLAM process:
July 12th - Storm at night - lots of water accumulated in pool.
July 13th PM - came home from work noticed the water has become slightly cloudy and green tinted (still could easily see the bottom). Measured chemicals - chlorine was 4.5ppm at this time, CYA was 30 which is what I have maintained it at, dropped pH a bit down to 7.2, upped my chlorine to 12-14 ppm. Water quite quickly turned from a green tint to a blue-whitish tint.
July 15th - I ended up turning pump off for the night, letting dead algae settle to bottom, and vacuumed floor to waste, this helped out a lot.
July 18th - maintained SLAM levels diligently until here, where water finally became crystal clear to my Wife's eyes, however to my eyes, was super clear but not really as crystal clear as it was before (maybe like 99.5% of the way there). Small fine particles seen with flashlight at night. I have passed OCLT every night since the 14th. We have been diligently brushing every couple hours to keep any dust in suspension to get it to pass through the filter.
July 26th (today) - I have been running chlorine at 8-10ppm every since - slightly above the max for my CYA, but below SLAM levels. Pool is neither getting any worse or any better, water still very clear but does not have that sparkle it did before. Between July 18th and 26th, I did a few OCLT and each time was no loss in chlorine. Pump was off for 15hours since yesterday evening, and some brown dust can be brushed up from the bottom of the pool.
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The filter can only catch particles that enter the skimmer, and the skimmer can only suck stuff in that’s floating on the top of the water. So DE in the filter, clarifier in the water, or even SLAM chlorine won’t remove stuff off the floor.
Sounds like you just need to keep brushing so the stuff gets into the skimmer or vacuum to waste. Sounds like the SLAM is done.
When there is as you decribe stuff on the floor and there's a MD I then valve off all and get the MD pulling hard. Then brush all towards the deep and all the fine stuff gets sucked in.
No main drain, only 1 skimmer. I been brushing quite often for a week straight. When the pump is running, I don't nice any dust clouds when brushing the ground so the stuff is always in suspension when the pump is running. So it must be going into my skimmer and into my filter. However since it hasn't been getting any better for a week of filtering now, I suspect that the filter filtered out 99% of the larger particles from my SLAM, and I am left with the extra small stuff that is not being trapped by the filter.
From my readings the general consensus is that sand can only filter down to 20 um in size, while living algae is like 2-7 um. However once dead and broken apart, the algae dust is probably even smaller. Logic does not make sense in everyone saying that this stuff that's well below 10 um I size will get filled out by a sand filter that can only do down to 20 um in size to get TPF crystal clear water after an Algae outbreak and SLAM. Can anyone explain?
I can't, but I can promise you it works. Consider the millions of sand filters in the US all not being able to filter out dead algae.
Well maybe 99.5% crystal clear water is what everyone is used to? I'm comparing to what water was like when I had the liner replaced and put in fresh clean tap water. The pool was sparkling crystal clear like this for a year and a half before it got away on me one night and I had to SLAM. Now it's super clean and clear but not as sparkling as before, but maybe this is as best that can be achieved with a sand filter due to the limit of sand filter filtering down to a minimum of 20 um and whatever left after a SLAM that is below this is just in the water now?
I'm looking at the water right now in daylight and I cannot see any particles at all floating in the water so it clearly filtered out everything visible to the naked eye.
There are plenty of sand filters in both of our water clarity pic contests
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We Have a Winner! TFP Pool of the Month (June 2023); Theme - Water Clarity
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If you maintained the sparkly fill water for a year with your sand filter, you filtered it *that* much. Add some DE to the filter to speed along that last little bit.
Add DE to a Sand Filter
A clean pool filter will increase the efficiency of your pool! ... your filter are to backwash it, clean the manifolds and grids, and add new DE.
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Cartridge, DE or a sand filter with DE added to it will to the naked eye even at night be very close in clarity. The difference between all is the time it takes to get to that point which a sand filter takes the longest. Also there is no knowing how large or small your filter is or if it's even working properly so go figure.
My filter is a Hayward sand filter that takes 100 lbs of sand so I think that's on the smaller side, but its also for a 4600g AGP. Pump is a Hayward 1HP pump.
OK so I added DE today. Filter was backwashed a few days ago and was still at the clean 12 PSI it normally is when backwashed. I added 1/4 cup at a time and noticed the needle would only go up slightly. Was also watching the return jet when adding the DE to the skimmer, and the return jet looked super clear so I don't think any DE was coming back into the pool. I kept adding 1/4 cup at a time until my PSI became stable at 13 (total of 2 cups). Everything seemed to go as per instructions in the DE to sand filter article so I think I don't have any channeling in my sand filter. I kept checking the filter pressure up to 20 minutes after adding the DE and it was stable at 13 PSI.
I brushed every half hour and I checked again 2 hours later and now the PSI is closer to 14 (went up almost additional 1 PSI so far). I am hoping this means that the fine dust is being captured, but can this also mean that the DE is just settling a bit more and increaseing the PSI even higher? I am planning to do a backwash once the filter gets up to 15-16PSI and then re-add DE. I was planning to run the pump over night, but with the PSI increase being so fast, I don't want to risk it with not being able to check the pressure often. So I will keep filtering until I go to sleep, then turn the pump on. Will see tomorrow morning if it has gotten clearer and if there is any more dust that has settled on the bottom when brushing. Then will continue to filter all day tomorrow. Very promising so far and hoping this will solve my issue.
OK so I added DE today. Filter was backwashed a few days ago and was still at the clean 12 PSI it normally is when backwashed. I added 1/4 cup at a time and noticed the needle would only go up slightly. Was also watching the return jet when adding the DE to the skimmer, and the return jet looked super clear so I don't think any DE was coming back into the pool. I kept adding 1/4 cup at a time until my PSI became stable at 13 (total of 2 cups). Everything seemed to go as per instructions in the DE to sand filter article so I think I don't have any channeling in my sand filter. I kept checking the filter pressure up to 20 minutes after adding the DE and it was stable at 13 PSI.
I brushed every half hour and I checked again 2 hours later and now the PSI is closer to 14 (went up almost additional 1 PSI so far). I am hoping this means that the fine dust is being captured, but can this also mean that the DE is just settling a bit more and increaseing the PSI even higher? I am planning to do a backwash once the filter gets up to 15-16PSI and then re-add DE. I was planning to run the pump over night, but with the PSI increase being so fast, I don't want to risk it with not being able to check the pressure often. So I will keep filtering until I go to sleep, then turn the pump on. Will see tomorrow morning if it has gotten clearer and if there is any more dust that has settled on the bottom when brushing. Then will continue to filter all day tomorrow. Very promising so far and hoping this will solve my issue.
The pressure rise means its capturing the stuff you want. Let it go to 18 psi before you backwash. No the DE doesn't settle like you think but it goes in-between the sand grains to tighten up the gaps to stop smaller junk.
OK sounds good then.
So yea, the sand was definitely not capturing this fine dust as once I backwashed, the gauge never moved from 12PSI even though I tried to filter this stuff for about a week.
So just a quick update from this morning. Last night before I went to sleep, the PSI was at 16 (clean=12psi, DE charged=13psi, took about 5 hours to get up to 16). Thinking that I would backwash around 18PSI, I let the pump run for 3 more hours into the night before it auto shot off.
This morning, the water looked more sparkly and clear. Since the pump was off for several hours at night, I decided to do the floor sweep test. To my surprise I was hard pressed to notice any visible cloud when brushing, definitely nothing like yesterday.
So I turned the pump back on to keep filtering and see what pressure it has reached. Thinking the pressure would should up to above 16PSI, it did something weird. The pressure only reached 13.5psi and stabilized - so only 0.5psi above DE filter pressure. Why would the PSI drop from 16+ last night compared to now 13.5psi when the pump turned off, rested for several hours then turned back on? Very confused.
I was planning to do a backwash this morning thinking it would be close to 18psi, but now it's so low. Should I backwash anyway and recharge with DE? Or should I keep filtering?
This morning, the water looked more sparkly and clear. Since the pump was off for several hours at night, I decided to do the floor sweep test. To my surprise I was hard pressed to notice any visible cloud when brushing, definitely nothing like yesterday.
So I turned the pump back on to keep filtering and see what pressure it has reached. Thinking the pressure would should up to above 16PSI, it did something weird. The pressure only reached 13.5psi and stabilized - so only 0.5psi above DE filter pressure. Why would the PSI drop from 16+ last night compared to now 13.5psi when the pump turned off, rested for several hours then turned back on? Very confused.
I was planning to do a backwash this morning thinking it would be close to 18psi, but now it's so low. Should I backwash anyway and recharge with DE? Or should I keep filtering?
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I'd try and stay in the medium dirty sweet spot as long as possible. If the PSI goes up, then backwash it.
The only explanation I can give is when the filter is off for a while the fine dirt retreats from where it's forced within the sand grains as there's no pressure behind it so naturally when you turned it on this morning it was a looser mixed and less pressure but as the filter runs it'll eventually get to where it was last evening and yet some so you will see the higher pressure again soon.
I was thinking along the same lines. Was just afraid that some of the dirt/DE blew threw the filter into the pool when I restarted but doesn't make sense as the pool water has definitely improved. Will keep filtering like this throughout the day today (filter is still 1.5 PSI higher above clean pressure). But just really happy that the water is looking more like it did before the SLAM now.
So after about 6 hours of brushing and DE filtering yesterday, and another 5 hours today, the water finally has its sparkle back. With sand alone, The water got clear but the dullness never got better after a week worth of filter, something that the addition of DE fixed in less than 12 hours of filtering.
I am not sure whether its my specific sand filter, the sand in the filter is bad, or whatever but I do not believe that I could have achieved sparkling clean water with the sand filter I have. I feel like it should be a prerequisite part of the SLAM protocol when using sand filters to add DE to go from clear but dull water to sparkling clear. I will definitely be charging up my sand filter with DE from now on after every backwash, especially now that I know exactly how much I need to add and that it doesn't blow back into the pool.
Thanks for all the help everyone!
I am not sure whether its my specific sand filter, the sand in the filter is bad, or whatever but I do not believe that I could have achieved sparkling clean water with the sand filter I have. I feel like it should be a prerequisite part of the SLAM protocol when using sand filters to add DE to go from clear but dull water to sparkling clear. I will definitely be charging up my sand filter with DE from now on after every backwash, especially now that I know exactly how much I need to add and that it doesn't blow back into the pool.
Thanks for all the help everyone!
When was the last time it was deep cleaned. We reccomend opening up any filter at least once a season to ensure everything is in working order, and while you're in there, clean it up.
It has not been done for over 3 years at least (we purchased the house 3 years ago - first time pool owner). I don't have any idea when or whether the previous owners did a deep clean so it might have been a while. Also not sure how old the sand is, whether chemicals such as clarifiers or flocculants were filtered through the sand, or when the last time the sand was replaced.
I didn't want to do this mid season this year, so my plan is to just get through the rest of this swim season and next spring before opening up the pool, I will open the sand tank and replace the sand inside (only 100lbs so it shouldn't be to difficult to do, just never done it before).
Sand doesn’t wear out so don’t replace just because. If it’s chunked up with floc, that’s a different story. It is a very small filter but the pool is small too, so maybe not a big deal.