SIlt (?) Collecting on Pool Bottom Every Morning

Steelfanman

Member
Aug 2, 2019
13
Peoria AZ
About a week ago I noticed what appears to be fine silt collecting on the table bench and in lesser quantity on the pool bottom. Repeated daily vacummings and brushings didn't stop it from reappearing every day after the nightly pump cycle. The quantity of silt seems to be about the same every day.

Three days ago I replaced the filter cartridges, thinking there may be micro tears in the old cartridges which are about 5 years old. Then I rebrushed/vacuumed the pool.

The silt did not reappear for 3 days and just this morning there it was again on the bottom of the pool and in larger quantity on the bench (maybe it built up slowly over the last 3 days and I didn't notice??). The water this morning was also cloudy compared to what it is usually. I took pics and vacuumed and took more pics, and you can see the before/after from this morning.

I've never had any problems filtering out any dirt, even after dust storms. There was a post on here kind of similar that led me to believe it COULD be algae, but if so it should not have disappeared for 3 days after the filter change, it doesn't seem to be getting worse, just the same amount, and my CC is normal. Plus I thought algae was green - it sure was the last time I had some!

This mornings test results:
FC = 6
CC <.5
ph=8.0 (immediately added acid, it is now 7.3 and the water is not as cloudy)
alk = 80
CYA = 60

Any ideas, suggestions, advice????


20200523_093144.jpg20200523_093158.jpg20200523_095739.jpg20200523_095752.jpg
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
33,711
Sebring, Florida
That is dead algae on your pool floor and bench. It gets there (and returns there) because you are killing some live algae (you can't see it) each day and the "algae carcasses" are settling on your pool floor.

You need to SLAM the pool and kill the algae with chlorine. Your filter will pick it up but if you kill more each day, the problem never goes away. That's the point of the SLAM......to eradicate ALL of the algae once and for all.

Do not think of this as a filtration problem......it is a chemistry problem.
 

Steelfanman

Member
Aug 2, 2019
13
Peoria AZ
I was afraid of that. Can I start SLAM tonight and still use the pool tomorrow, or is that amount of chlorine bad to float around in? (still too cold to actually swim). Or if I want to use the pool should I wait to SLAM until after the weekend but keep the chlorine high, knowing I may still get the "dirt" in the mornings? Seems like I could hold off if I want to use the pool tomorrow since the issue hasn't gotten worse.

My FC never tests lower than 4 when I test and chlorinate at night, meaning it's 6-7 most of the day, so I'm a little frustrated I've got a problem now.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,218
Laughlin, NV
You can safely swim in a pool as long as the FC is above the minimum and at or below SLAM level based on your CYA. You must also be able to see the bottom of the pool in the deep end of the pool.

Do you brush those small flow areas often? How much flow goes through them normally?
 

Steelfanman

Member
Aug 2, 2019
13
Peoria AZ
I can see the bottom very well (as the pictures show), but it's just not QUITE as crystal clear as usual. - a bit cloudy that improved during the time I ran the pump lowering the ph this morning. but not completely today.

I brush the pool when I need to - usually when there is debris in the dead areas the pop-ups don't completely cover, or after a dust storm. Not usually a problem in the winter, so I didn't brush much at all until a few weeks. But I guess I should more often regardless of whether I think I need to or not?

If the pool is already almost clear, and my CC is already <0.5, how do I know when to end SLAM? The overnight FC loss test?

You mentioned running that test tonight, but after today the FC is probably around 4 right now. Wouldn't I want to start SLAM instead rather than risk a further drop in FC since I'm not supposed to add any during the test?

Sorry....so many questions! Very helpful though.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,218
Laughlin, NV
Having 'silt' which is dead algae means you do not have clear water. That is the number one criteria for a successful SLAM.

You can run a Overnight Chlorine Loss Test at nearly any FC. Best if 10% or greater of CYA.

Your pool. You can leave it be and see how it goes. If you can live with what you have, great.
 

Steelfanman

Member
Aug 2, 2019
13
Peoria AZ
So I upped the chlorine last evening and ran the Overnight Chlorine Loss Test and these are the results:

FC 10pm last night: 10.5
FC 8am this morning: 10.0 (maybe 10.5 but the pink I detected at 10 might have been confirmation bias)
CC: I dont think it turned pink at all.

There was "silt" on the bench this morning. I didn't see any cloudyness looking into the deep part today, it looks pretty normal other than the dusting on the bottom (see before and after pics of brushing on the bottom, and the "silt" on the bench this morning).

To me it doesn't make much sense based on the test results, but that's why I'm here for more advice.

20200524_091810.jpg20200524_092555.jpg20200524_091829.jpg
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,218
Laughlin, NV
Sounds good. Go with your normal maintenance.

If there is any way to capture some of the debris, put it on a paper towel and smear it. If it has a green tinge to it, it is algae.
 

Steelfanman

Member
Aug 2, 2019
13
Peoria AZ
Thanks. It's going my way as far as chemistry is concerned, but going back to my original post and the questions I asked there - what could be going on where silt collects in this location (and on the bottom to a lesser extent) some mornings after the pump has run all night?

The pump program runs a nightly 4 hour high rpm clean cycle then a 4 hour low rpm circulation cycle. I'm guessing by the pattern on the bench the silt settles during the circulation cycle. But it doesn't settle in the usual areas of the pool where small debris not collected during the cleaning cycle usually collects .

This issue has only started happening in the last week or so and isn't accompanied by anything else unusual that I can point to except what I describe above and the actions I have taken so far to eliminate the issue.
 

Rocco

Well-known member
Dec 23, 2012
257
Manassas Park, VA
I recommend you fill a bucket with water and place it beside the pool. If the bucket of water also has the silt then you can confirm this is something coming into the pool from the outside. Here in Northern Va we have a lot of pollen at this time and it can settle on the pool floor as well.
 

Steelfanman

Member
Aug 2, 2019
13
Peoria AZ
Thanks for the advice everyone. I like the bucket idea, I am going to try that. My yard is fenced in and we have tile shingles (and no rain) so I'm ruling that out.
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,414
Houston, Texas
It looks like corse sand to me. It looks like you have rocks behind the pool in your avatar. Could be that the corse sand is coming from the rock landscaping. How has the wind been in your area lately?
 

Saturn94

Well-known member
Mar 11, 2015
872
SE Virginia
So I upped the chlorine last evening and ran the Overnight Chlorine Loss Test and these are the results:

FC 10pm last night: 10.5
FC 8am this morning: 10.0 (maybe 10.5 but the pink I detected at 10 might have been confirmation bias)
CC: I dont think it turned pink at all.

There was "silt" on the bench this morning. I didn't see any cloudyness looking into the deep part today, it looks pretty normal other than the dusting on the bottom (see before and after pics of brushing on the bottom, and the "silt" on the bench this morning).

To me it doesn't make much sense based on the test results, but that's why I'm here for more advice.

View attachment 141382View attachment 141383View attachment 141384
On that 3rd pic it looks like most of the dirt is below an expansion joint. Perhap you have ants digging in there and dumping the sand/dirt into the pool?
 

Steelfanman

Member
Aug 2, 2019
13
Peoria AZ
It looks like corse sand to me. It looks like you have rocks behind the pool in your avatar. Could be that the corse sand is coming from the rock landscaping. How has the wind been in your area lately?
It has been pretty windy lately. If it wasn't for the quantity of dirt, I would have thought the wind was to blame. Even dust storms don't leave this much, and not usually in that area of the pool, but hopefully you are right. The bucket test I am running now will hopefully confirm it.

On that 3rd pic it looks like most of the dirt is below an expansion joint. Perhap you have ants digging in there and dumping the sand/dirt into the pool?
Haven't seen any ants around the deck but I'll keep a lookout for them.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
33,711
Sebring, Florida
That is dead algae on your pool floor and bench.
No, it isn't. It's obviously sand/dirt. I am sorry that I guessed at that. Experience has taught me on this forum that that issue will be algae 95 times out of 100 but I guessed nevertheless. I would not pursue "algae" as your problem.....it is sand.

So, if this sand suddenly appeared a weeks or so ago, can you recall any changes you made to the pool at that time? It looks too coarse to be blown in.

Curious.....why are you calling it "silt". Silt is powdery and close to mud........your pics look like clean washed sand.