Help me diagnose my pool

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pieter3d

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Aug 17, 2009
12
Gilbert, AZ
First off: Pool is pebble, in ground, chlorine, about 12000 gallons (I think). All chemical tests are within limits according to my local pool shop. 300lbs sand filter.

Lately I have been getting very fine dust on the bottom, where the creeper doesn't reach. I can easily brush or vacuum it away, but it just shows up again the next day. Because of this you can always see a dark and light area on the bottom from where the creeper reaches, and the water is never 100% clear. I was worried one of the laterals had broken in the filter or something, so I emptied it out to check them, but they are all fine. Also put in new sand (regular #20 silica sand), and of course backwashed before using it.
The dust/sand in the pool is extremely fine, if i move my hand near it it just billows up, so I am thinking it is just too fine for the filter to handle and just gets pumped right back into the pool. Also the dust has kind of a greenish tint to it, but it isn't algae, since it settles and forms little ripple patterns on the bottom from the current, just like sand at the beach.

I backwash, shock and de-phosphate regularly, keep tablets in etc. I tried using a clarifier, both an 8oz dose and half a bottle, neither helped. I diluted it with a bucket of water as per the instructions first. At this point I am kind of at a loss, and not sure what else I can try, short of buying and installing a DE filter.


Picture was taken a while back.
IMG_0992.JPG
 
Welcome to TFP!!

The only way to know for sure whether it's algae or not is with good test numbers!

Have you read Pool School?

The honest truth is that there is NO other pool site you could log on to to get the advice you need :!: However, we need more info about your pool and what's going on to be able to definitively help you :( Sounds like you probably have too much cya in the water, but we'd need some test numbers (from a decent test kit!) to even begin to start to help you.

Have you read Pool School? (It's linked in my sig - and also at the top right of every page)

We are here for you! :whoot: But we need more info on your pool, especially the chem levels :cool:
 
Hi pieter3d ,

I see you have met waste (a/k/a Ted) and, as usual, he has given exlcellent advice! :goodjob:

Yep, we need the info listed in the first article of Pool School to give you the best help.

Welcome to the forum :wave:
 
If you are lucky, it's just dust that the filter can't catch. Brand-new sand is usually pretty good, but with sand you don't want it too clean--it actually works a little better when slightly dirty. One thing that some people do is add about 1/2 lb DE to the sand filter; it is especially helpful with old sand, not sure it will help much with new sand. If you have a main drain, brush the stuff down toward the drain and we'll see if the filter can catch it the 2nd or 3rd time around.

You are chlorinating with trichlor tablets. This has gotten your CYA up very high, and your FC is too low for the high CYA level. According to Pool School's Chlorine/CYA chart with CYA 100 you need to keep FC above 7 at all times, and preferably up more like 12.

But, with CYA that high, we usually recommend replacing water to lower the CYA (that's the only way). Where do you live and how much sun does the pool get? That will help us figure out what a reasonable CYA target is.
--paulr
 
Hi, I'm in Phoenix. I'd say, if it is greenish, then it's algae perhaps mixed with dust/dirt and it could very well be mustard algae. Dust/dirt here looks dark brown when it settles on the bottom, not greenish.

Your CYA of 100 means you need to keep your minimum FC at 8ppm and max at 13ppm. Your shock level is 25 and your mustard algae shock level is 54. Keeping your FC at 5 is under enough to have a slight algae problem but strong enough to probably keep it from going full bore. You need to take care if it, regardless.

So, you either need to shock with liquid chlorine and keep your chlorine levels up that high or do a series of backwashing and replacing water a little at a time until your CYA is reduced. You need to stop using tri-chlor tablets and dichlor based shock because it is just adding to your CYA problem. Cal Hypo is also usually not good to use because we naturally have a high calcium level in our water. You shouldn't drain much at a time when the temperature is above 90.
 
Hey,

Welcome to the forum. Your water issues are almost surely algae related.

You will need to shock the pool but would be very wise to do as Buggsw and PaulR suggests and do a partial drian and refill (you can even do them simultaneously) and get your CYA down around 60.

It will be much easier to clear your pool from that point.
 
Ah, Arizona, land of majorly hard water... what's your CH? I notice that isn't in the list you posted earlier.

With that much sun I'd shoot for replacing a total of 1/4 to 1/3 of your water, CYA in the 60-70 range is not uncommon in that environment.
--paulr
 

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lovingHDTV said:
Don't panic of your CYA still measures 100, as 100 is the highest you can measure without diluting the sample. This just means that your CYA was over 100 and you need to do some more water drain/refill.
Click to expand...
Oh, right, yeah, I knew that could be the case, uh huh. :oops:

After the refill finishes, and the fresh water has had maybe an hour with the pump on to mix in, try the CYA test again. If it still shows 100+, do this:
- Pour the content of the mixing bottle (and view tube) into some other cup.
- Fill the mixing bottle half full with tap water.
- Top it off with the stuff from the other cup.
Now you've diluted your sample, and you can try the view-tube part of the test again. Double the result, natch.
This extends the range of the test (with some loss of accuracy but not enough to matter in your situation).

--paulr
 
Thanks for all the tips guys. All this time I have been using the tablets with the floating dispenser thing, and dichlor shock, on advice from the pool shops. It seems like everyone would run into this problem eventually using that. Guess I'll be buying bleach from now on.
 
Yes this is a common thread for pool maintenance.

My neighbor pays a local company to maintain his pool. Every other year they do a complete drain to fix his pool as it is "over stabilized". Then they leave him with a case of di-chlor shock for his weekly shocking.

He has a cartridge filter so he never backwashes. No wonder he over stabilizes his pool so often.

dave
 
It is a huge issue for a lot of people, they just don't know the root cause. They work around the real problem by shocking their pool everytime it rains, someone swims in it, there is too much sunshine, someone looked at it wrong, phase of the moon, or it hasn't been shocked in more than 48 hours. They might also spend tons of money on all kinds of chemicals to fix all of the problems they have because the pool store tells them that is what they should do. These are the same people that will tell you that a pool is a huge money pit and takes several hours a week to maintain. In reality, none of this stuff (including shocking) is required if the chlorine level is always kept within the effective range for the amount of stabilizer in your water.

The secret to keeping CYA in check is to chlorinate with clorine only instead of products such as Trichlor that contain CYA or other ingredients. Liquid chlorine (or bleach) or a SWG are all good options for chlorinating without adding other junk.
 
The pool store today looked at me weird for wanting to use liquid chlorine, saying it would be gone within a day or 2, and it is only really for shocking. They seem to think I couldn't deal with tending to the pool every day.

How much liquid bleach should I be using? I think they have 10% strength. Are we talking about gallons per week or what?
 

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