Dusty Bottom/Cloudy Water Issues

[MattTexas]

I have a 15x30 AG pool that was installed last year. About 11000 gallons. It has a Heyward pump and sand filter with multiport valve - it can vacuum to waste and recirculate.

About filtration media: The sand tank has zeolyte. According to label recommendations on the zeolyte, when I installed it last year, I only included about HALF the amount of recommended sand. Until now, I haven't had filtration issues, but the tank DID get shaken around a lot while I had it winterized - It even got rolled on its side some. However, it was sealed at that time.

About location of pool: pool is located partially underneath a pecan tree. Due to the nature of our yard, we just didn't have a choice here when we installed it.

Chemistry:
Ph=7.4
Alk = 125
CYA = 40-ish
FC = 3.0 (last test for CC, about 3 days ago, was at <.5)
CH = circa 380 (I have trouble reading the color change on this test)
Phosphates - my pool store tested today and indicated no phosphates

Here is the problem: The pool has been opened since mid-March. From the start, I noticed that a very fine brown-ish "dust" was settling in the crevices of the pool, particularly along the edges. In addition, during the last few weeks, it has rained 2-3 times. After raining, the bottom of the pool tends to develop green patches, and a very fine layer of what I would call "dust" tends to fall across the bottom of the pool. When the pool is in this condition, water clarity is very good, but the walls and ladder tend to start turning green.

In response to this, I always shock and brush. I also add algaecide. Chlorine levels tend to go down to about 3ppm overnight and I then maintain them there. I run the pump constantly. I also run an automated cleaner on the bottom of the pool for about 3 hours. If I brush again the next day, I can see that I am again stirring up a layer of "dust" off the bottom of the pool.

The green continues to gather in a few isolated patches on the walls overnight, and I can also see a layer of green covering various crevices in the portion of the ladder that is in the pool.

The pool is blue-cloudy - moreso after I brush and less so several hours later. I can see the bottom of the pool, and even see the walls/bottom on the opposite side of the pool, but it is still obviously cloudy. I have tried water clarifiers and organic enzymes as well as oxidizing shock. Nothing seems to help.

I haven't yet tried this, but I suspect that, if I turned off the pump overnight, all of the cloudiness in the water will disappear as the "dust" settles back on the bottom. I'll end up with clear water and a cruddy looking layer of the dust-like stuff on the bottom.

Here are the things I HAVEN'T yet tried:

1. Let it settle on the bottom and vacuum to waste
2. Try to maintain FC at 15 until it clears (I've seen this recommended on the boards here)
3. Check for filtration problems (Don't really know how to do this)

Any suggestions?

[aylad]

Hi, and welcome to the forum!!

It sounds like you're not completely killing the algae before you let your chlorine drift down. With a CYA around 40, you need to run your chlorine level up to 15 ppm and hold it there not just overnight, but until you can go overnight without losing more than 1 ppm of chlorine. This usually takes more than one day....but it's the only way to really kill off the algae. You need to thoroughly brush the pool just after the chlorine addition, as well, with special attention to the places that you know the green is growing. Don't add anymore clarifiers, algaecides, or other goop--just plain chlorine will do the trick.

Regarding filtration problems--do you have a working pressure gauge on your filter? When you run your pump, does the pressure rise any? When you backwash, what color is the stuff coming out? You can check your filter (and with the treatment you describe it got during closing, I would!) by adding a handful of DE to your skimmer and watching the returns to see if it blows back into the pool. If it does, then your filter will need some work. If not, then the DE will coat the sand in the filter and will help it collect finer stuff than the sand would alone.

How are you testing your water?

[MattTexas]

Janet-

Thanks for the quick reply! I do have a working pressure gauge. It rises whenever my pump is primed and the system is set on filter, but it never seems to increase in pressure from there. I have backwashed a couple of times in the last 2-3 days. The first time, I got LOTS of green. The second day, I got some brown. It does seem to be catching stuff - more generally speaking, whenever I backwash, I tend to get a lot of brown water before the stream clears up.

Any suggestions on the best place to buy DE?

Re, my testing: I have a K-2006 kit. For day-to-day/quick-n-dirty readings, I also keep a FAS-DPD kit handy.

[aylad]

Just re-read your post and realized that you have zeo instead of sand--don't add any of the DE to it yet, let me check with Pooldoc or one of the other filter gurus and make sure that it won't create problems. You can get DE at a pool store, but I think I also saw Ben post a smaller quantity that he found through Amazon. At any rate, don't add it it until Ben says it's okay....

Janet

[MattTexas]

An update: yesterday I chlorinated the pool in a manner calculated to get it well above 15ppm. I didn't do my K-2006 test on it this morning, but the DPD test kit showed it was still WELL over 5 ppm. Based on the very dark color of the liquid, I think it probably held pretty well overnight, but the DPD kit won't register the exact reading above 5ppm.

[Watermom]

Like Janet said above, you need to maintain shock level until you can go from sundown one evening until within 2 hours of sunrise without losing more than 1ppm of chlorine, and you have no greater than 0.5CC. Then, we usually suggest holding the chlorine high for one additional day for added insurance. Only then, can you let the chlorine drift down. So, you really need to use your K-2006 kit so you can accurately see what is going on.

[MattTexas]

Got it.

Is it okay to let it drift down to 15ppm, assuming it is higher than that right now? 15ppm is the amount recommended by Janet, but I had shocked it at a higher level last night before I saw her post. Not sure, but when I do a K-2006 reading on it, it might still be higher than 15ppm at sundown today. <G>

- Matt

[Watermom]

Yes, it is ok to let it come down to 15. Test it this evening and if it hasn't dropped to 15ppm, don't add any more chlorine. If it has, add enough chlorine to take it back up to 15. By the way, what are you using to chlorinate with?

[MattTexas]

I'm using this stuff: http://www.lesliespool.com/Home/Pool...ock/14181.html

I apply it into the skimmer. Yeah, I know (now) that I could use bleach from the grocery store, but I bought this in bulk, so I thought I might as well keep using it as long as I have it. Do you see anything about it that could be harmful? My assumption is it is just granular chlorine that dissolves quickly.

I'd also kind-of like to know for future reference. I want to support my local pool store, and I don't mind buying chlorine there, even if its more than I'd pay for grocery items at Wal-Mart.

[MattTexas]

Update: last night I brought the level up to 15ppm. As of about 2 hours after dawn this morning, I had lost 2ppm (reading was 13). No growth showing on walls. A little less cloudy, but there is a large buildup of brown-ish "dust" in the crevices of the floor.

On a related note: anyone have advice on whether I should put some DE in the skimmer basket to test the filter and to help the filter catch smaller particles? I have zeo sand in my filter.