Why is there so much dirt on the bottom of my pool?

mang

Member
Sep 2, 2012
6
I have to vacuum the complete bottom every 2-3 days - very powdery dirt/dist settles to bottom and covers in a brown film. First started happening during first week of July here in St. Louis - multiple weeks of 100+ degrees. I live in a new home development where there has been non-stop construction digging foundations, grading, etc. on about 10 large home, and, until this past week (due to remnants of hurricane Isaac, very little rain).

The water is clear (from a distance), but once in the pool, lots of crud on surface and suspended in the water can be seen with goggles underwater. Vacuuming has been stirring up some of the bottom.

I test my water with a Poolmaster Basic 5 test kit and once a week at the retail store for the company that built the pool.

Is there something chemically wrong in my numbers? Total Chlorine 5.9; Free Chlorine 5.9; pH 8.2; Alk 130; Calcium Hardness 75; Salt 2900. I ran my Goldline Aqualite system on Super Chlorinate a day before so my Chlorine is high but will be on its way down.

I backwash for 2 minutes and rinse for 1.5 minutes after each vacuum )my pressure gage never goes above 20psi. When I close down the other inlets to drive all the suction through my hose for vacuuming, the filter shows 15psi.

Is it possible that I have some type of scaling or just that much dirt in the air?

Appreciate any help you can give me. I had a pool service come once a week last season and this season I took over. However, no houses were under construction last summer near my house and there were no drought conditions like this year.

I also wondered if the potential added load of the dust and dirt is overwhelming my filter's capacity. While the design rate is 98GPM, I believe that the pump is generating closer to 50GPM at 1.5HP and what looks like a 1.5" pipe.
 

duraleigh

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Welcome to the forum. :lol: I would speculate that what you are seeing is not dirt but dead algae. The best way to tell is to capture some and feel if it is gritty or just dissipates between your fingers.

On another subject, you need to get your pH down right away. Should be around 7.5 and yours may be quite a bit higher than 8.2.
 

mang

Member
Sep 2, 2012
6
Thanks so much for your input. I had that thought about dead algae -- it indeed does just dissipate in my fingers -- the fact that there is so much 'real' gritty dirt as well on the pool bottom was greatly confusing to me . Since my water is not green - where is this algae coming from - could it be resident in the filter itself -- where is it living before it winds up dead on the bottom of my pool? (hopefully not too dumb of a question form this rookie)
 

zea3

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You don't list a test result for CYA. If the chlorine is too low for the CYA level you can have algae that is constantly growing and being killed, with a full algae bloom being held at bay until the FC drops a little more.
 

duraleigh

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Algae can be present in your pool and you not see it..... until the chlorine kills SOME of it and it falls to the floor
 

mang

Member
Sep 2, 2012
6
So, it looks like I may be in for shocking my pool. I had been told by my pool center that running the salt system in "super chlorinate" mode was the equivalent of shocking the pool.

Now, I understand that a certain FC level must be reached and maintained during the shocking period to insure a complete kill and that level depends on where the CYA level is.

But first, I must get my pH down from 8.2 to something like 7.2 or the effectiveness of the FC will be diminished.

So, sounds like my first step is to put some muriatic acid into the pool tonight and test pH in the morning.

I will also need a source of chlorine i.e. bleach since my SWG will not get to high enough FC fast enough.

Thanks for your helpful comments and the "Pool School" resource.

I also need to get better testing capability at home.
 

duraleigh

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mang,

Everything you posted is correct. There is a small chance you do not need to shock the pool but I doubt it so....


1. Reduce your pH using muriatic acid

2. Elevate your chlorine to around 16ppm and then hold it there until your pool is crystal clear.

3. Run the pump 24/7 and vacuum and brush often. Clean the filter as needed.

4. You have picked up a lot from Pool School....keep reading up there and ask questions....we'll all help.
 

zea3

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After you have completed the shock process raise the CYA to 70 if you plan to continue using the saltwater chlorine generator.
 

mang

Member
Sep 2, 2012
6
Thanks for all the help, from everybody. I have a bit more confidence today than I did yesterday. I am glad I found this resource.

I only had 48 oz of muriatic for last night and put that in. Looks by my test this morning that I am below 8 but in high 7s. My test for acid requirements says I need about 2 quarts more to get to 7.2 so I am off to pick some up.

I don't have test capability to determine FC beyond 5 at home and 10 at the pool company. It only shows that I max'd the home test at some number above 5 and the pool company shows pegged at 10 but I do not know how much above I am.

I did order the TF-100 kit yesterday so it will be a few days before that arrives - I think that will get me the ability to see higher FC numbers.
 

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Stuamurr

LifeTime Supporter
With all that construction dust it may well be undissolved particulate matter that is too fine for the filter to trap. I had a similar problem. Have you been vacuuming to waste or just on normal filter mode? Does it return to the bottom after around 2 days when you just vacuum to filter?

Definitely consider it may be dead algae, but what you describe, sounds like you just have fine dust particulate in your water that needs to be vacuumed down the drain.

Regards
Stuart
 

mang

Member
Sep 2, 2012
6
Stuart:

The fine particulate was my operative theory all along - others in the area say this has been the worst year for dirt in the pool. It has truly been a rough year of being a slave to pool care. I will definitely look for an auto vac option for next season.

I have, on several occasions vacuumed to waste and I think that it helps to simply get the junk, whatever it is, out. Due to drought conditions, I have been a little sensitive to how much water I throw out of the pool to waste vs. backwashing/rinsing, so I can't do it every two days that way. It is a large pool and takes hours to vac esp with the amount of material that is on the bottom.

I think I'll go through the shock approach to see if that makes a difference. Whether I shock or not, I am still going to get the dirt but will have the peace of mind that it is not a combination of algae and airborne particles from construction.

Thanks much for your comment and suggestion.
 
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