Persistent fine dirt on bottom of pool.

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PrivatePilot

PrivatePilot

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Jun 13, 2013
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So, for about a year now I have been having issues with persistent fine silt building up at the bottom of my pool.

I can vacuum it up, but a day later it’s once again right back where it started.

On a few occasions I’ve vacuumed to waste which solves the problem, however given it’s only a 12x16x4 inground it ends up consuming a surprising amount of water (Even with the VSP on a low-ish speed sufficient to vacuum) that then needs to be replaced with fresh (and very cold) water. And then usually within a week or three, it’s back anyways.

The root of the problem seems to be debris not getting caught by my sand filter - question is, why.

I’ve tried DE to no avail.

Sand was last changed about 3 years ago and we only have a 5 month pool season here so I don’t think that’s the issue.

Are there any super fine filtering skimmer sock solutions or something that could be used during vacuuming to remove this debris before it simply gets sucked up by the vacuum and then eventually blown right back into the pool?

My water is otherwise crystal clear, no issues.

Thanks everyone.
 
You have been around since 2013 so I assume you have a quality test kit and understand the TFP method of pool chemistry. Post your recent test results. Describe your sanitation program. Your situation sounds like the all too familiar rising algae population so starting the diagnosis there.
 
It’s absolutely not algae, like I said, pool is crystal clear, liner not slippery anywhere, etc. I’m very familiar with all the signs of algae issues and this is not it.

I tried to take a photo however it didn’t attach for some reason. The debris collects in little ripples on the bottom of the pool as it would when you’d floc and let it settle. If you jump in they dissipate back into the water in an instant, but then effect clarity.

Water is balanced. Salt water pool. BBB method.

Its definitely a filtration issue. I’m just waiting for someone to tell me that it’s likely a broken or damaged lateral, but I’m trying to kid myself that’s not the probable issue. And in the meantime, at least until the end of this season, find at least a temporary method of letting me filter it out during vacuuming without vacuuming to waste. 😉
 
Mark,

Sounds like algae to me also.. Just because you pool is clear does not mean you don't have algae.

The good news is that a clear pool with algae is pretty easy to fix with a quick SLAM..

What is your CYA, what FC # are you trying to maintain, how are you chlorinating your pool?

Thanks,

Jim R.
 
Just checked... FC is actually nearly 6. Has been hovering in the 4-5 range consistently in the last 2-3 weeks. Need to turn down the SWG clearly.

CYA is admittedly low, but with a FC of 6 (and never lower than 4-5 in the last several weeks) I know the pool and it's use well enough to be able to say that without a shadow of a doubt a FC crash hasn't occurred in the last month. Or at all this season, for that matter.

And like I said in the title, this has been a reasonably persistent issue for around a year and there's also 0.0% chance that in 2 seasons I've been having algae issues all this time. Had higher/normal CYA last season and had the issue then as well.

I really wish the photo had attached however I've since jumped into the pool and dispersed it all so I can't get another until tomorrow.
 
So, because you are pretty darn sure it is not algae, do you have any idea what it might be? ANY correctly working sand filter will filter out ANY visible debris. Do you think your sand filter is broken?
 
Filter issues?

That’s ultimately what I’m asking.

And what I suspect it is - however, in the interest of not assuming, I’m working here towards ruling out other possibilities first but I’m not sure people are reading the entirety of my posts and replies before jumping to conclusions based on the outcomes of the millions of others newbies who come here and complain of debris floating in their pool which turn out to be basic chlorine level issues. 😉

I’m not a pool newbie. I’m not against learning, and I’m not automatically dismissing the replies suggesting it’s algae related, but every single observation I’ve made thus far seems to me to rule it out as a possibility. With a FC that’s been consistently north of 5 and about 16 hours of a day of filtration (solar through the day, a lower speed filtration cycle on the VSP through the overnight hours) it doesn’t seem to be a hospitable environment for algae?
 
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It is possible that it could be dead algae. Usually it is smaller than what a sand filter can collect. However, DE usually will trap it. How much DE did you add and what was the pressure rise when added it?
 
I'd say it was around 1 cup of DE added - enough to get a 1PSI rise on the filter as per the how-to here.

The thing that makes me wonder if this is a filter issue or not is that I'm not seeing any signs of filter sand on the bottom of the pool, so every time I start to think this might just be a broken or damaged lateral, wouldn't I also be seeing sand?
 

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Mark,

I did read your whole post, but that does not change my opinion of the problem.. That said, I could very well be wrong, but then so could you.. :)

Part of troubleshooting is eliminating possible causes... If I had your pool, I would take it up to SLAM level for a couple of days and see if the dust did not magically disappear.

One of my first rules of troubleshooting is to never believe what the guy who was working on it before you had to say, unless you verified it yourself. Or maybe in your case, never believe the gear is down unless it has been verified, during that flight, not the past flights.. :mrgreen:

Thanks,

Jim R.
 
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Mark,

You seem pretty resistant to SLAMing, if your pool is clear now it should only take a few days to rule out algae and then you just cross it off the list. If I were you, I would slam (because it's the rational thing to do to eliminate algae as the cause).
 
I have read all your posts as well......in their entirety. Again. Since it is NOT algae (your words), you have to come up with something else it might be. You don't see any filter sand on the pool floor and you have added some DE for even finer filtration and nothing. That pretty much eliminates filtration, doesn't it? Repeating, a working sand filter will not allow anything visible to pass back to your pool

I am stumped for ANY explanation as to what this debris might be.

AN OCLT indicates the presence of algae but it is NOT a rock solid promise that you have no algae even when you pass it. We have multiple reports every swim season of people who pass an OCLT but have visible algae......however small.
 
From the symptoms I very much doubt that it’s a broken lateral. The function of the laterals is stop the sand from escaping the filter and ending up in the pool. But the openings in a functional lateral are big enough that fine particles could still fit through. The sand stops the fine particles and the laterals stop the sand. So if you did have a broken lateral what I would expect to see is sand getting into your pool, not fine particles. Unless the problem has been going on for so long that a significant amount of your sand has already made it into the pool and you no longer have enough sand left to properly filter the water.

It may be that there are channels in your sand and the sand is no longer filtering properly, however, if that was the case and the sand is really in that bad of shape then I suspect that it wouldn’t be able to hold back the DE media as well. I would expect that when you add DE to the skimmer that a significant amount of it would pass right through the filter and come out into the pool. But it doesn’t sound like that’s the case.

I might even go so far as to try to get some fine dust or dirt that might be easier to see than DE in the pool and put a little of that in the skimmer and watch the returns to see if it passes through the filter. If not, then I don’t think it’s a filter issue. If it does, then you can spend more time looking at the filter.
 
I assume your dirt is the super-fine stuff that I get occasionally, so I'll throw my .02 in as well. :)
Have you had abnormal amounts of rain? My pool gets dusty dirt at the bottom from the dirt that rain brings with it.
Is there any construction near you (homes, roads, etc)? That could be a source as well.
 
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