Maybe a low level algae problem that I cannot kill??

[Pauls234]

Hello all,

Short question - could algae "hide" or grow in retaining wall blocks given how porous they are? I continue to get dead algae on the floor, clean it up, go through the SLAM process, pass the 3 criteria, only to have it very slowly reappear dead on the floor and I am wondering if the retaining wall blocks that I use (edit) to weigh down my ladder(end edit) are its home. I've brushed them, and don't visually see anything. Are they just generally a bad idea?

For the usual suspects, I've brushed the ladder and don't visually see anything there (would I see algae if it were growing there?)

The only light I have is the return eyeball and I cannot remove that without draining down the water level, but this seems like an unlikely source given the constant circulation.


Here is my background for the last few days, in case it helps, I use the recommended test kit:

While my water stays clear and I pass the OCLT and CCs have never shown up on my tests, I continue to see what I believe is dead algae accumulate on the bottom. I vacuum it up, and within several days, it is back. I keep a solar cover on almost all of the time and the cover itself does not appear to accumulate any filth, so there is little evidence pointing to it just being dirt.

I raised to shock level again Wednesday night (17ppm for my CYA of 40), wife tested yesterday around 3pm (20 hours later) and FC was down to 11, so definitely something in there that is consuming it, particularly given that I left the cover on this whole time. I raised back to shock, then tested last night for the OCLT. Tested 17ppm before bed, then 17.5 ppm this morning (assuming a small testing error in there somewhere) so I passed there. I've gone through a similar exercise 2-3 times over the past month.

 

[duraleigh]

I am wondering if the retaining wall blocks that I use are its home.

Are you saying you have retaining wall blocks in your pool?

 

[Pauls234]

I do, and realize now how funny that sounds without a few key words that I erroneously left out!

I am wondering if the retaining wall blocks that I use [to weigh down my ladder] are its home.

I'll edit the initial.... but really what am I asking is, am I playing with fire because they are porous, or is that really no more/no less of a concern than the liner or plastic ladder, or solar cover, etc.

 

[linen]

Yes, I could see the blocks being a harbor for algae, since it may be difficult for the water to circulate in and through them. With that said, if you pool gets a lot of sun, going from 17 to 11 ppm FC during the day at 40 ppm cya is not unusual.

I would check a sample of the stuff on the bottom to see if it is slimy or if it is dirt (usually small grains of "sand").

 

[duraleigh]

Algae loves any hidey-hole. Water doesn't circulate well so the chlorine doesn't get in their to kill it. I'm not sure if the blocks are the exact source of your issue but I am certain they are not helping.

Why do you think the algae is returning? Even with the blocks, that is not something I would expect after the SLAM.

Are you maintaining CONSTANT adequate chlorine after you SLAM? What is your CYA level?

On a different subject, constantly covering your pool is not good practice. Pools like to breathe fresh air every day or every couple of days at least.

 

[Pauls234]

Linen,

Hard for me to say if it is dirt or algae by feel. It doesn't exactly feel slimy to me, but it is just too voluminous and persistent to be dirt, relative what has gathered on the bottom of my pool in the past. There is also no real source of dirt in the area, i.e. no construction sites or dirt roads, and lastly, if it was dirt, I would expect to be seeing it gather on the top railing, solar cover, and deck which I don't. The 17 to 11 is very high for me as I had the cover on. In June and July I was often losing only .5-1 ppm each day, plus I got another pile of whatever it is on the floor again this morning after a thorough vacuum yesterday. It is these reasons why I'm leaning towards dead algae and not dirt, though the water is always clear.

Dave,

I've actually been keeping my FC levels somewhere between target and shock for this past month just to be safe, my CYA is 40 and have been keeping my FC from 6-9. I'm totally stumped as you can tell, so I'm kind of grasping.

What else can I do? Figure I'll clean the filter just for the heck of it (pressure has only moved up 10% from clean, 10-11), remove and brush the blocks again and try get through the end of the season. Then, seal up the blocks for next year? What else could I use to weigh down the ladder? I'm not using bags of sand, did that once and had one break open so went to the blocks. If it is the blocks, should that be obvious through a visual inspection?

 

[linen]

In June and July I was often losing only .5-1 ppm each day

But I would assume your FC level was much lower? FC loss to the sun is a percentage of total FC. 6/17= 35%...1ppm/0.36= ~ 3ppm starting FC, and of course down at those FC levels the test uncertainy could be higher.

A solar cover will not block all of the uv rays from the sun. What type of cover do you have?

With that said, it could be something bypassing your filter. Did your filter pressure go up during the SLAM process?

 

[duraleigh]

I agree your results are a bit puzzling so always go back to a clear, hard fact.........Chlorine is consumed by only 2 things - sunlight and organics in your pool.

How or why they got there seems hard to justify but, once you eliminate sunlight, organics (algae) is the only acceptable answer.

If it was my pool, I think I would SLAM it.

 

[linen]

Figure I'll clean the filter just for the heck of it (pressure has only moved up 10% from clean, 10-11)

Whoops I missed this comment. If you pressure only went up that much during your SLAM process, it seems that the dead algae could be bypassing the filter. Make sure you inspect it closely when you clean it.

 

[Pauls234]

I agree your results are a bit puzzling so always go back to a clear, hard fact.........Chlorine is consumed by only 2 things - sunlight and organics in your pool.

How or why they got there seems hard to justify but, once you eliminate sunlight, organics (algae) is the only acceptable answer.

If it was my pool, I think I would SLAM it.

But that's the part that is really puzzling me. I go through SLAM, pass the 3 criteria very quickly, and end up with slow build up of dead algae over the next several days as I allow the FC level to drift down. This is why I was speculating on a low level algae problem that I am just not finding. Most recently, I started SLAM Wednesday night, continued through Thursday, and then passed the OCLT this morning (Friday), no CCs and water is clear as long as you don't count whatever is sitting on the bottom. Maybe it is finally dead this time....

Linen - how would it be bypassing the filter? A hole in the cartridge? Would it require a lot of holes or just a couple? What am I looking for when I inspect?

Thanks again to you both for your help in thinking through this, at least I have a few more things to try.

 

[linen]

I does not take much of a hole to basically bypass the filter. Also look for a possibility of a poorly seated filter, or damaged end.

 

[Pauls234]

Quickly, just tested fc at 16.5 so almost zero consumption in the last 22 hours. I also cleaned tje cartridge which was filthy! Didn't see obvious damage or holes, so maybe it's just a dirty filter issue

 

[linen]

Does you gauge go to 0 when the pump is off?

 

[Pauls234]

It used to, but I checked that today and noticed it only falls to 3 or so. What does that mean besides it's probably bad?

 

[Pauls234]

In other words, is it overstating, understating, or just useless altogether?

 

[linen]

Hard to say, it may be overstating the pressure, but once they go bad (as yours has) then they are unreliable and need to be replaced. I would use the google search at near the upper right to search the site on liquid filled pressure gauges. They last much longer.

 

[Pauls234]

So, I finally broke the filter down to clean and inspect the cartridge over the weekend. It wasn't all that dirty, but I did find one a tear, perhaps large enough to fit the tip of my finger into. It actually appears to be a manuafacturer defect, or imperfection. Where it is located, the pleat doesn't go nearly as deep as the others, almost like they were glued together and then pulled apart leading to the tear, if that makes any sense. I attempted to glue it back together using fabertac, not sure if it will hold.

Would this one hole be enough to cause so much to bypass the filter? The cartridge is not that old, purchased last July.

 

[linen]

Would this one hole be enough to cause so much to bypass the filter? The cartridge is not that old, purchased last July.

I would guess that is your culprit.

 

[Pauls234]

thanks, just surprising given that the hole accounts for probably 1% or less of the total surface area of the filter! But, when you rule out the impossible.....

 

[linen]

Well a lot of water (and debris) is going to find that hole since it is the path of least resistance.