It's a pentair 150 cartridge filter. I backwashed it twice at end of the "extended" SLAM. CYA is 35-40 now unless I'm not reading CYA correctly. For that black dot to be completely gone I'd be at 20 CYA or less...
Struggling with Algae
- Thread starter Ksbguy
- Start date
A cartridge filter is normally not set up for backwashing, its feasible, but it may be best to just open it and clean it thoroughly.
The CYA test can be challenging. We all have struggled however, if the dot doesn’t completely disappear until 20 then your CYA may be too low and you are losing FC to UV affect, which then allows any algae to take hold again. That is why it is good to run your FC at top end of the range.
Also, you may want to try this method for reading your CYA as I find it easier and avoids staring at the dot as you pour.
Pour the mixed solution to a known level, say 90, peer in and confirm you can see black dot. Now pour mixed solution to 80 mark, peer in again, if you can still see dot, hold tube up and pour mixed solution to the 70 mark, then peer in again to view dot. Continue this until you are not able to see the dot - then use your CYA number as the value you last saw the dot. This method avoids constantly looking down the tube which can create the illusion of always seeing the dot due to staring down the tube. This also helps that you only report CYA values in decade numbers due to the logarithmic scale of the tube.
Also, you are using LC, so raising your CYA to 50 is a good target for start of swim season. However, Let’s get rid of the algae before you raise your CYA. You may need to consider another SLAM to get rid of what is left. I would clean the cartridge filter first to remove any lingering algae in there.
By backwashing I mean I remove the filter and use running water on the outside of the filter media to clean. Just checked it again and brown, no algae on filter.
This morning I have no algae, it's crystal clear, seems to come and go. I'm also not sure now if I'm seeing dust/pollen when brushing....
The pool guys I see here close one eye and hold the tube a few inches away from the open eye. If I do that it's 35, if I hold it at my waist I can fill the tube all the way to the top and some black dot is visible. The pool stores say it's 40. But my FC level never drops more than 1 - 1.5ppm/day. Since the SLAM it has not been below 5, I've tested daily and also tested 30 minutes after adding to make sure that pool math is correct for the size pool I entered and it is. I'm adding 24-32oz of liquid CL daily. If I see it at 5 I put it to 6.5-7 given it never looses more than 1.5 and won't drop below 5.
Given that my CYA is probably lower than 40, 5 - 7 CL should be plenty according to the chart.
I think I need to do the test in areas where I see this happen to see what FC is after the pump stays off overnight, maybe it's dropping below 4 in those areas. I changed the returns to point down after the SLAM to try and improve flow to bottom of pool if that is the case.
Chlorine (as well as most other additives) does not "pool up" Once mixed, It distributes evenly throughout your pool.
Last edited:
That could be accurate. Appears you have everything else handled and maintained.
So it's not possible for levels to drop a bit in certain areas after pump sits off overnight more than others? Others here have suggested that could be occurring hence why I was going to check.
Not really possible.
Now, if you fail to run your pump, the water will begin to stratify from temperature rise but if you manage your pool correctly. You should get the same test results at any location in your pool.
Now, if you fail to run your pump, the water will begin to stratify from temperature rise but if you manage your pool correctly. You should get the same test results at any location in your pool.
Agree with @duraleigh Liquid chlorine is hydrophilic, it rapidly disperses in a column of water. So only a small amount of actual mixing is needed.
- Jun 1, 2018
- 16,027
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Previously I was referring to checking for areas of poor circulation in the pool. For instance, I have wedding cake steps that have areas in them where the water doesn’t flow well so I had to add holes to remedy that.
The pump runs for 12 hours at 45gpm so I'm turning pool over about 2.3 times. It runs 8am to 8pm. Good?
We teach to run it enough to keep your pool clean. Vague, I know, but you will get a good feel for what your pool requires. My bet is you can cut it back to around 2-3 every 24.
I'm at a loss with this. I'm 100% certain SLAM was done properly (I went an extra two days) maintained FC 5 - 7 after (lowest I saw was 5 testing daily) and the algae came back. There's no phosphates, nitrates, anything in this water. CYA is 35, It was 40 the last time I checked hence I was maintaining 5 - 7 FC.
I have a tab feeder I don't use that I leave full open so the FC flows through there and I always also see algae in there when this happens. I don't see how since the water entering it would be chlorinated but without a tab in there is it possible it's starting in there?
I have a tab feeder I don't use that I leave full open so the FC flows through there and I always also see algae in there when this happens. I don't see how since the water entering it would be chlorinated but without a tab in there is it possible it's starting in there?
It would be very helpful for your signature to be filled in. Use link below in my signature to get started. Can you provide the full gama of the most recent test and post please.
You have done most everything right but something is missing. Let's walk you through another SLAM that should be quite brief and we'll get your pool crystal clear........promise. Our procedures are based on science and pretty much infallible.
The best way to start is to complete a new set of tests and then post them up. Tell us what your water looks like. Also would be helpful to fill out your signature.....it'll keep us from asking redundant questions.
The best way to start is to complete a new set of tests and then post them up. Tell us what your water looks like. Also would be helpful to fill out your signature.....it'll keep us from asking redundant questions.
A tab feeder could be one of the areas, especially if you turn your pump off. The tab feeder has a check valve on the bottom, so it possibly is allowing it to drain the receptacle when the pump stops which could allow algae to form. Other places of concern are light niches, under the rungs of a ladder, etc.
Our methodology for SLAM has worked for many, many members, so something is a little off as to why you are still fighting algae.
Also, for future discoussion, we round up the CYA test to the highest decade number. As you can see, the distance between each of decade lines is different because the scale is logarithmic. So rather than guessing the number, just round up to the decade line that you last saw the dot. So for your latest test, round 35 to 40 and the SLAM level FC would be 16ppm If you pursue another SLAM.
It's full blown algae hunting time. It's likely hiding in plain sight. Ladder rails, light niches, autofills, etc. Every inch is suspect until it's been drained/cleaned.
Behind weir door under skimmer baskets and have seen it in the autofill sump too.
- Jun 1, 2018
- 16,027
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Yup, check ALL the crannies! It’s hiding somewhere.
Jump on the
SLAM Process asap before it gets any worse.
Once you’ve scoured all the hiding places & pass all 3 end of slam criteria aim for a scootch above high target
for fc & see how you fare.
Jump on the
SLAM Process asap before it gets any worse.
Once you’ve scoured all the hiding places & pass all 3 end of slam criteria aim for a scootch above high target
for fc & see how you fare.I really appreciate all the help!
Signature filled out. I've covered every inch of this pool, there is no visible algae anywhere. I performed another SLAM until I had 0ppm FC drop overnight and no visible algae. The pool is crystal clear, been here before many times... I put a tab in that feeder and closed the flow, my theory is it starts in there. There are no rails, ladders, anything in this pool aside from a sun-shelf with two bubblers.
TA - 50
FC - 9 Currently coming off SLAM (keep 5 - 7)
CYA 40. To be honest here for me to not see that dot at all I have to fill it to the top of the tube at waist level. The dot is cloudy at 40 but still visible so it's probably lower.
CH 350
PH 7.6
Signature filled out. I've covered every inch of this pool, there is no visible algae anywhere. I performed another SLAM until I had 0ppm FC drop overnight and no visible algae. The pool is crystal clear, been here before many times... I put a tab in that feeder and closed the flow, my theory is it starts in there. There are no rails, ladders, anything in this pool aside from a sun-shelf with two bubblers.
TA - 50
FC - 9 Currently coming off SLAM (keep 5 - 7)
CYA 40. To be honest here for me to not see that dot at all I have to fill it to the top of the tube at waist level. The dot is cloudy at 40 but still visible so it's probably lower.
CH 350
PH 7.6