New pool owner here. I've been having this problem for a couple months now. When I first got the pool, I was having an issue with my filter losing suction within 5 mins. My pool guy came out an opened the sand filter and took the top layer off, said cottonwood buildup was the culprit. Ever since then, every single day the entire bottom of the pool is covered in little piles of dead algae. I thought it was sand at first but it disappears into the water if you go near it, and is noticeably green if brushed. My pool has never been green and the chemicals are constantly maintained. If i vacuum to waste and turn the filter off and leave it off, the piles of dead algae do not return. I've tested this for days on end, they don't reappear. Within 1 hour of the filter being turned on the bottom is covered again. My pool guy suggested filter cleaner and DE powder, both did nothing. I've vacuumed to waste a dozen times but the issue persists. Any suggestions?
Dead algae piles daily coming from the filter.
- Thread starter gjantz
- Start date
You need to take the water testing into your own hands with one of the kits
Test Kits Compared in the link. Also read up on the following
Pool Care Basics
FC/CYA Levels
PoolMath
Overnight Chlorine Loss Test
SLAM Process
The filter won't stop the algae from growing and only sanitization of the water via chlorine will hep.
Test Kits Compared in the link. Also read up on the following
Pool Care Basics
FC/CYA Levels
PoolMath
Overnight Chlorine Loss Test
SLAM Process
The filter won't stop the algae from growing and only sanitization of the water via chlorine will hep.
- May 27, 2021
- 1,281
- Pool Size
- 17000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Ok, dumb question……but because you didn’t specify I’ll ask. Did he replace the sand he removed? All indications point to algae and improper sanitization, however if your filter is low on media it will not filter effectively. Follow advice above and confirm if you can that the filter was topped up with appropriate media.
In my opinion, "Dead Algae" is mostly not a real thing.
Unless you have really bad algae and you kill it with chlorine, you are not going to have dead algae.
In my opinion, most reports of dead algae are mustard algae, especially if the dust has any color other than white.
Green, brown, yellow, olive etc. all indicate live algae.
Algae mostly gets oxidized to carbon dioxide.
Unless you have really bad algae and you kill it with chlorine, you are not going to have dead algae.
In my opinion, most reports of dead algae are mustard algae, especially if the dust has any color other than white.
Green, brown, yellow, olive etc. all indicate live algae.
Algae mostly gets oxidized to carbon dioxide.
Must be a sand filter. Too low on sand, and extremely dirty. Do a deep clean, as instructed part way down in this post: Deep Cleaning a Sand Filter
Make sure the lower laterals are not damaged. Some sand filters are not as good at capturing things as others. Yours seems to be, but is overloaded for the amount of sand in it, and is recirculating a portion back into the pool.
Since you see green - you have algae. Valid testing as detailed previously, and doing a SLAM. After the filter cleaning, vacuum the stuff on the bottom out to waste, so you reduce the amount of backwashing/future deep cleaning you may have to do.
You don't say what chems at what levels it has been maintained - but the root of the matter is not enough Chlorine to prevent the algae.
I fear to differ with JamesW, as he really, really knows his stuff - but it could be dead algae. Along with lots that is still growing. Alive or dead, it has to get out of the system one way or the other. That means lots of Cl over time, and frequent cleanings.
Make sure the lower laterals are not damaged. Some sand filters are not as good at capturing things as others. Yours seems to be, but is overloaded for the amount of sand in it, and is recirculating a portion back into the pool.
Since you see green - you have algae. Valid testing as detailed previously, and doing a SLAM. After the filter cleaning, vacuum the stuff on the bottom out to waste, so you reduce the amount of backwashing/future deep cleaning you may have to do.
You don't say what chems at what levels it has been maintained - but the root of the matter is not enough Chlorine to prevent the algae.
I fear to differ with JamesW, as he really, really knows his stuff - but it could be dead algae. Along with lots that is still growing. Alive or dead, it has to get out of the system one way or the other. That means lots of Cl over time, and frequent cleanings.
Hi All,
Thanks so much for all the input.
@wireform I will review your suggested content.
@JamesW I will share pictures after work tonight. My first thought when this started happening was that it was mustard algae after looking at pictures. Of course the pool company I deal with told me it's not that. The more I talk with them, the lest I trust them. After all my conversations with them trying to rid myself of this issue they finally contradicted themselves and told me this was normal and something I'd just have to deal with. I know at least 10 people with a pool and none of them have ever had this so I knew it was time to go elsewhere. The one thing I really don't understand is why does it only occur if the filter runs... that makes no sense to me and really had me thinking the filter itself is infested and pushing into the pool.
@Lake Placid No, I don't believe so. It was only a single handful, is that little amount a concern?
@sande005 Yes, sand filter but I'm really considering buying a cartridge filter next season.... I'll take a look at that topic about cleaning it. I use the strips my pool company recommended to keep the chemical levels balanced. SPARCO 5way test strips, FC around 3ppm, PH between 7.2 -7.8, alkalinity between 80-120ppm, and stabalizer at 100ppm. And I have them test the water once a month for the difference in TC and FC. Though after finding this forum I see this is not a good way to go about it and obviously will have to follow the recommendations here on water testing.
My immediate concern now is that here in MI the temps are dropping quick, was down to 40 last night and I really need to get the pool closed. I planned on doing it next week. I don't know if I'm going to have enough time to get the recommending water testing kit and go through the SLAM process before it starts frosting. I've only just briefly read about it but seems like a lengthy process. Would it be detrimental to close it with this issue active?
Thanks so much for all the input.
@wireform I will review your suggested content.
@JamesW I will share pictures after work tonight. My first thought when this started happening was that it was mustard algae after looking at pictures. Of course the pool company I deal with told me it's not that. The more I talk with them, the lest I trust them. After all my conversations with them trying to rid myself of this issue they finally contradicted themselves and told me this was normal and something I'd just have to deal with. I know at least 10 people with a pool and none of them have ever had this so I knew it was time to go elsewhere. The one thing I really don't understand is why does it only occur if the filter runs... that makes no sense to me and really had me thinking the filter itself is infested and pushing into the pool.
@Lake Placid No, I don't believe so. It was only a single handful, is that little amount a concern?
@sande005 Yes, sand filter but I'm really considering buying a cartridge filter next season.... I'll take a look at that topic about cleaning it. I use the strips my pool company recommended to keep the chemical levels balanced. SPARCO 5way test strips, FC around 3ppm, PH between 7.2 -7.8, alkalinity between 80-120ppm, and stabalizer at 100ppm. And I have them test the water once a month for the difference in TC and FC. Though after finding this forum I see this is not a good way to go about it and obviously will have to follow the recommendations here on water testing.
My immediate concern now is that here in MI the temps are dropping quick, was down to 40 last night and I really need to get the pool closed. I planned on doing it next week. I don't know if I'm going to have enough time to get the recommending water testing kit and go through the SLAM process before it starts frosting. I've only just briefly read about it but seems like a lengthy process. Would it be detrimental to close it with this issue active?
This is common with mustard algae.
Probably not a big risk if you close without fully clearing especially if you have a solid cover.
Some types of algae would be a big problem like black algae because that can embed into the pool surfaces.
Most likely, you can SLAM in the Spring after opening.
Note that there is some risk of the algae growing by a lot if it is not completely removed by a SLAM, so you are taking some risk, but probably not a lot.
You also risk getting bacteria because the existing algae will eat up the chlorine and leave the pool open to bacterial growth.
- May 27, 2021
- 1,281
- Pool Size
- 17000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
No it is not. If a large amount of sand had been removed and not replaced, the effectiveness of your filter to clear the water would be in question. That’s not the case here.
Attachments
Can you explain more about why it's common for mustard algae to reappear only when the filter runs?
I am not sure why it happens.
I suspect that it accumulates in the filter and goes through with water flow.
It doesn't only reappear when the filter is on in all cases.
Mustard algae acts different from other types of algae in several ways.
Despite slamming for over a week the issue still persists. It definitely has reduced, not nearly the accumulation per day as before. However, after the first 3 days its been at the same level since. I have no choice but to close the pool, can't wait any longer. Aside from that, I can't get an accurate CC level since I have hundreds of leaves entering the pool daily at this time of year. I'm wondering if changing the sand before opening next year is a good idea, I have an inkling there may be a flow path in there the water is following and not sufficiently getting cleaned.
- Jun 7, 2024
- 410
- Pool Size
- 7300
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Intex Krystal Clear
Your choice whether to replace at some point or not. Sand doesn't ever wear out. New sand will be extremely dusty, so has to be mega rinsed before firing up the filter. So take out your old sand, and inspect the lower laterals and other components to see if they need repair. Put either your old sand back, or the new. Use the deep cleaning method I linked to earlier to rinse either all the dirt/debris out of the old, or dust out of the new. You'll then have clean sand either way. Reassemble and bring it back into operation.
Dust in the sand depends on brand, in my experience. HTH is very low dust, quikrete seems to be entirely dust and no sand (slight exaggeration, but only slight). Those are the only two brands I have experience with.
Have you been brushing daily? I just dealt with mustard algae in my pool, and even when I was sure it was gone, brushing the bottom would kick up a big, colorless cloud. Water was clear and the bottom looked totally clean, but brushing proved it wasn't! Mustard algae seems really sneaky... I never had overnight chlorine loss or CC (maybe one day CC was almost 0.5, because the water barely took on a hint of pink). But it kept coming back until I slammed and then mustard algae slammed. I plan to keep pH lower and FC higher next season.
I've read that you can add some DE to a sand filter to catch finer particles. If you backwash near a stream, probably not (can harm fish). But maybe worth researching over the winter
- Jun 7, 2024
- 410
- Pool Size
- 7300
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Intex Krystal Clear
Adding DE helped with my SLAM. It’s a simple process. Trying to find a small amount is the challenge.I've read that you can add some DE to a sand filter to catch finer particles. If you backwash near a stream, probably not (can harm fish). But maybe worth researching over the winter
Sand Filter Use and Care - Further Reading
www.troublefreepool.com